732 FXUS66 KSEW 240230 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 730 PM PDT Wed Apr 23 2025 .SYNOPSIS...High pressure will build over the region through Thursday, with dry and warming conditions. Cooler and wetter weather will move in later this weekend, with a return of drier and warmer weather possible towards the latter half of next week. && .SHORT TERM /TONIGHT THROUGH SATURDAY/...Another evening under the ridge with clear skies in place over W WA. Some low 60s still in place over the south Sound and SW interior at the time of this writing, while remaining obs find themselves in the mid to upper 50s. Inherited forecast remains on track with no need for evening updates. For additional forecast details, please refer to the Previous Discussion section below. 18 From Previous Discussion...Upper level ridging will continue to build over the region through Thursday for dry and warm conditions. Temperatures this afternoon have been warming steadily into the mid to upper 60s, with some localized spots in 70s. Temperatures will warm a touch more on Thursday, with most of the interior locations seeing temperatures in the lower 70s - areas along the water will see highs close to the mid 60s. A weak trough offshore will start to increase cloud cover slightly heading into Friday, as a cutoff low continues to move southward into California. Latest ensemble guidance has continued this track of a southward progression, which would decrease precipitation chances for western Washington. High temperatures on Friday will continue to be the upper 60s/lower 70s. A split flow regime looks to set up heading into the weekend, with Saturday looking to be mainly dry and temperatures in the low to mid 60s. .LONG TERM /SUNDAY THROUGH WEDNESDAY/...Split flow will slightly differ as a upper trough opens way for precipitation chances on Sunday. Ensembles are having a difficult time grasping on the strength and spread of precipitation as it seems weak, but overall, it looks generally light, if any precip, on Sunday. Showers may linger through midweek before drier weather returns. Mazurkiewicz && .AVIATION...An upper level ridge axis over the coastal waters will shift onshore tonight with north to northwest flow aloft becoming light southerly overnight. The low level flow remains northerly. The air mass is dry and stable. Mostly clear skies expected through the period except for some patchy stratus along the coast and locally in the Chehalis Gap on Thursday morning. KSEA...VFR. Surface winds north/northwesterly 5 to 8 knots becoming light northeasterly tonight then north/northwesterly 7 to 10 knots once again Thursday afternoon. 27 && .MARINE...A surface ridge centered offshore will weaken through tomorrow. A broad area of weak surface low pressure will develop late in the week over the Pacific Northwest while high pressure remains centered well offshore. This will lead to an overall increase in onshore flow leading into the upcoming weekend. The end result will likely be a period of small craft advisory winds across the coastal waters as well as the central/east portions of the strait. 27 && .HYDROLOGY...No river flooding is expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

888 FXUS66 KPQR 240447 AFDPQR Area Forecast Discussion National Weather Service Portland OR 947 PM PDT Wed Apr 23 2025 .UPDATED AVIATION DISCUSSION... && .SYNOPSIS...High pressure will maintain dry weather and mostly clear skies through Thursday afternoon. An approaching system will bring a 15 to 20 percent chance of thunderstorms Thursday evening across the Linn and Lane County Cascades as well as the southern Willamette Valley. Cooler temperatures and mostly dry conditions expected this weekend with lingering showers over the Cascades. && .SHORT TERM...Now through Friday Night...High pressure will maintain dry weather with mostly clear skies across northwest Oregon and southwest Washington through tomorrow (Thursday) morning. Expect this afternoon`s highs in the upper 60s to low 70s for interior valleys, and upper 50s to low 60s along the coast. Tomorrow is forecast to be the warmest day of the week, with highs in the mid to upper 70s for interior valleys. Can`t rule out reaching 80 degrees in the greater Portland/Vancouver Metro Area, with NBM suggesting a 40-60% probability of certain areas exceeding 80 degrees. Overnight lows remain seasonably cool, generally in the 40s. Winds will be light and out of the northwest today, with gusts up to 20-25 mph along the coast. Tomorrow, a weak thermal trough moving northward will return 5-15 mph easterly winds for coastal and inland areas north of Tillamook and Salem. Thursday evening (mainly 3-11 PM Thursday), an upper-level trough will approach the Pacific Northwest, turning flow aloft more southerly to southeasterly. This pattern will favor more moisture advection from the south, as well as elevated instability as cooler air moves in aloft. The latest HREF guidance shows MUCAPE values between 100-400 J/kg across the Linn/Lane County Cascades and southern Willamette Valley, which is enough to produce some isolated thunderstorms. Taking a look at HREF soundings, wind speeds aloft look weak (no stronger than 20-30 kt) and directional wind shear looks minimal, so any thunderstorms that develop are expected to be sub-severe. The soundings are also showing some of that instability tapping into the -10 to -30 deg C hail growth zone. Therefore, potential impacts from any isolated thunderstorms would be lightning, small hail (likely bb-sized), brief downpours, and brief gusty outflow winds. NBM doesn`t capture elevated thunderstorms very well, so went ahead and increased thunderstorm probabilities to 15-20% (slight chance) for the Linn/Lane County Cascades and southern Willamette Valley Thursday evening. Will note that the south-southeast steering flow aloft could push some convective debris into the Coast Range or even the coast. The slight chance for thunderstorms will diminish late Thursday night into early Friday morning as instability aloft decreases. Friday is beginning to trend drier for more locations west of the Cascades. Guidance is tracking the upper level trough more southeastward into California. Therefore, the highest probabilities for precipitation remain across the Cascades (50-80%) as showers wrap around the low. West of the Cascades, probability of precipitation has decreased to around 15-40%. Many locations may see at most a sprinkle or remain completely dry. The probability of 24 hour rainfall exceeding 0.25 inch (5 AM Friday to 5 AM Saturday) has fallen to 10-20% west of the Cascades, and 30-60% in the Cascades (highest over the Linn/Lane County Cascades). With the low tracking further south, skies are trending more scattered or broken the closer you get to the Portland/Vancouver Metro and southwest Washington. This is leading to warmer forecast temperatures on Friday for interior valleys, with upper 60s to low 70s especially north of Salem. -Alviz .LONG TERM...Saturday through Tuesday...As the aforementioned upper level trough continues to move into the Intermountain West, cooler air will settle into the area and precipitation chances will gradually decrease. Daytime highs are forecast to fall into the 60s across interior valleys. Most areas will remain dry, but the Cascades may continue to see some lingering showers. Heading into early next week (Monday-Tuesday), the majority of GFS, Euro, and Canadian ensemble members are showing an upper level ridge shifting into the Pacific Northwest, leading to slightly warmer temperatures. However, about 25% of ensemble members do show a shortwave trough coming in by Tuesday, so there remains some slight chances for precipitation early next week. -Alviz && .AVIATION...VFR conditions are expected to persist at most sites going through the forecast period. Winds are out of the north to northwest but will eventually shift offshore overnight into Thursday morning. This will help maintain clear skies, however, one potential exception is at KONP where offshore winds may be too weak to prevent the development of low stratus which is already slowly forming along the south Oregon coast. Expect a drop to MVFR/IFR CIGs where this stratus forms. It`s also worth noting right towards the end of the TAF period (after ~22-23z) we`ll need to keep an eye on the potential for isolated shower and thunderstorm development in the Lane County Cascades/foothills southward - confidence was too low to mention in the KEUG TAF. PDX AND APPROACHES...VFR conditions and clear skies continue through the TAF period with northwest winds around 5-10 kt turning more easterly during the day on Thursday. -Schuldt && .MARINE... Strong high pressure offshore will maintain northerly to northwesterly winds across the coastal waters through the upcoming weekend. The strongest winds expected at any time this week are occurring right now due to a surface thermal trough along the south Oregon coast tightening the surface pressure gradient over the coastal waters, resulting in breezy north winds with gusts up to 20-30 kt and seas around 5 to 7 ft. Expect these conditions to continue through Wednesday evening. A Small Craft Advisory remains in effect for all marine zones (except the Columbia River Bar) until 11 PM tonight. The thermal trough will break down Wednesday night, allowing winds to ease Wednesday night into Thursday. Seas are expected to persist around 5 to 8 ft at 10 to 12 seconds through Friday. -TK && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

210 FXUS66 KMFR 240514 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1014 PM PDT Wed Apr 23 2025 .UPDATE...Updated Aviation Discussion. && .AVIATION...24/06Z TAFs...Along the coast, MVFR ceilings are developing and will become widespread tonight with a mix of MVFR/IFR conditions, including at North Bend (KOTH), lasting into Thursday morning. Conditions will lift of MVFR along the coast in the late morning and afternoon, with IFR returning Thursday evening. Inland, expect mainly VFR except for areas of MVFR stratus spreading into northwest Douglas county, mainly northwest of Roseburg (KRBG). There is about 20% chance of occurrence for brief MVFR/IFR around sunrise at Roseburg though. Scattered showers will develop Thursday afternoon and evening with low thunder chances (15-25%) at both Medford and Roseburg. East of the Cascades, expect a 10-15% chance for showers and isolated thunderstorms, including at Klamath Falls (KLMT). && .PREV DISCUSSION... /Issued 803 PM PDT Wed Apr 23 2025/ UPDATE...Updated Marine Discussion. MARINE...Moderate north winds will gradually lower overnight. Winds should drop below small craft levels by early Thursday morning, but seas will remain just elevated enough for Small Craft conditions to continue through late Thursday morning. Calmer conditions are likely Thursday afternoon through Friday as low pressure moves to the south. Showers are likely during this time period, then stronger north winds and steep seas are possible again by Saturday afternoon. PREV DISCUSSION... /Issued 154 PM PDT Wed Apr 23 2025/ DISCUSSION...Satellite imagery shows a mid-level disturbance moving east of the Cascades this afternoon with some convective/congested cumulus across SE portions of the CWA. These extend from southern Klamath and eastern Siskiyou counties eastward across Modoc and southern Lake counties. Any showers and isolated thunderstorms that manage to develop this afternoon will diminish and end this evening as the upper trough axis shifts east of the area. Best chance for thunder (still less than 20%) will be over the Warner Mtns south of Lakeview. Otherwise, it`s a nice afternoon out there in most other areas with sunny skies and temperatures about 5-8F above normal. A weak upper short wave ridge will move in overnight into early Thursday morning with dry conditions, though marine stratus will likely revisit coastal locations/Coquille Basin (it`s already forming near Cape Arago). The next upper trough digging offshore will allow the flow to back to the SSE on Thursday. It`ll remain mild in advance of this system, so high temps will be similar to where they are today. A short wave disturbance in the SSE flow aloft will arrive across NorCal Thursday afternoon. Instability parameters are modest with about 100-500 J/KG of MUCAPE, but also some decent mid-level moisture moving in aloft. This will provide enough lift to generate some showers, especially from the Cascades westward (Siskiyou County north-northwestward) during Thursday afternoon and into Thursday evening. These probably get going around 2-4 pm and propagate off toward the NNW through early Thursday evening. Probability of showers during this time frame is 40-60% across the west side, with thunder chances mostly in the 20-40% chance range. Activity should be more isolated over the East Side Thursday afternoon/evening. The upper trough will develop into a closed low off the NorCal coast Thursday night, which will maintain showers over our area Thursday night through Saturday, but also with a cooling trend (high temps back to near or even below normal). The low eventually moves eastward across California and into southern Nevada by Sunday morning. Showers will be most numerous in the afternoons/evenings coinciding with peak heating/instability and there is still a slight chance of thunderstorms. The focus will be near the mountains and west of the Cascades through Friday, then south and east of the Cascades on Saturday. Convective showers are quite difficult to assess just exactly where and how much precipitation there will be. But, amounts of 0.25-0.75 of an inch appear to be most likely with this event, some places (mountains) receiving a little more and some (valleys) a little less. Heights begin to rise Sunday, though there is still a chance of showers over the mountains and SE portions of the CWA. It`ll remain on the cool side, but should be mostly nice for outdoor activities. Models then show more pronounced upper ridging arriving on Monday with temps rebounding to above normal levels. Aside from a weak trough swinging by to the north on Tuesday, the ridge should amplify into mid next with temperatures getting back close to 80F here in Medford by Wednesday. -Spilde && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Thursday for PZZ350-356-370-376. Hazardous Seas Warning until 11 PM PDT this evening for PZZ356- 376. && $$

944 FXUS66 KEKA 232159 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 259 PM PDT Wed Apr 23 2025 .SYNOPSIS...An upper level trough approaching the area will bring cooler temperatures each across the interior through Saturday. There is a slight chance for thunderstorms over the mountains each afternoon as well. More widespread showers are expected to bring rain to most areas on Friday. Cool nights and pleasant sunny afternoons will return Sunday and into next week. && .DISCUSSION...Water vapor satellite shows a trough moving over the area this afternoon. This is bringing cooler temperatures to the area this afternoon. Quite a few cumulus clouds have developed over the mountains, but as of 1:30pm they are fairly flat. These may produce a shower or even a lightning strike, but confidence is low on this. Tonight frost is possible again in the coldest valleys of Trinity county, but with all the CU around it may keep temperatures in the upper 30s. So for now have not issued a frost advisory. Closer to the coast widespread marine clouds are expected to develop around sunset or shortly after. Thursday afternoon inland areas are expected to see a number of showers and possibly some thunderstorms as well. CAPE varies quite a bit of model to model, but the HREF mean is showing around 200 j/kg. Shear is only around 20 kt and mid level lapse rates are generally around 6.5 to 7c/km. This will likely be enough to generate a few thunderstorms Thursday afternoon. Thursday night into Friday showers are expected to become more widespread as the upper level trough moves. There is the potential for some thunderstorms again Friday afternoon, but in general it looks like there will be too many clouds around to generate enough daytime heating and instability. Saturday the upper level low starts to move out of the area, but there is expected to be a resurgence of showers in the afternoon with the daytime heating. High temperatures across the area expected to struggle to break 60 degrees even in the warmer areas. Overnight lows are not expected to drop too much due to the moisture and clouds around. Any areas that do remain clear Saturday night could see some frost. Sunday clearing skies are expected and temperatures will start to warm back up again. Inland areas are expected to see highs in the 60s. Sunday night into Monday morning is expected to be the coldest night and frost is possible in the colder valleys. High pressure continues to build in through the week with highs around 80 for the inland areas by Wednesday. MKK && .AVIATION...Banks of fog prevailed along much of the North Coast this morning...especially over Humboldt Bay to ACV where a thin layer lingered into early afternoon. However, webcam and satellite imagery showed a different picture. Perhaps the lingering BKN017 layer at ACV (became sct018 at 1324 LST) can be attributed to sea spray? Low clouds over Mendocino could not overtop the coastal range... therefore UKI remained SKC. A weaker coastal gradient resulted in less gusty winds at CEC. Overnight/Thursday: All model guidances return stratus along the coast, with Cigs expected from low MVFR to IFR, most notably at ACV. River valleys will also develop stratus with UKI possibly getting a brief morning period of IFR/MVFR Cigs. By later day Thursday, local airports could be slightly impacted by weak convection/showers. /TA && .MARINE...Northerly winds are easing and will continue to trend downward tonight. Seas will drop below 10 foot in all zones going into early Thursday morning, but advisory level steep seas will be slower to drop off going into midday Thursday. Of note, there will be a pronounced and persistent wind eddy for the far northern inner zone and around Point St George starting tonight around 8 pm. The resulting localized southerly return flow will generate southerly winds with gusts up to over over 18 kts tonight. In fact, models retain this feature through most of Thursday. A weather system will move in on Thursday and weaken the pressure gradient. As a result, winds Thursday afternoon will generally range from 10 to 15 kts, with lower winds and seas of 5 ft on Friday. Behind this system, northerly winds will then begin slowly increasing Friday night, and will continue strengthening through Saturday. Winds of up to 25 kts are forecast Saturday evening, and this similar magnitude of northerly winds can be expected into next week. There is currently a low probability for winds over 25 kts (30- 40%) through that period, and mainly for the afternoons south of Cape Mendocino and Point St George. /JJW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 AM PDT Thursday for PZZ450-455. Small Craft Advisory until 11 AM PDT Thursday for PZZ470-475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png

885 FXUS66 KMTR 240447 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 947 PM PDT Wed Apr 23 2025 ...New AVIATION... .SYNOPSIS... Issued at 140 PM PDT Wed Apr 23 2025 Cooler conditions prevail through the weekend. An approaching cut-off low will bring light rain to the Bay Area and Central Coast this weekend with up to 0.5" possible across the Santa Lucia Range. A low chance of thunderstorms exists Friday through Saturday morning. && .UPDATE... Issued at 838 PM PDT Wed Apr 23 2025 No changes to the forecast this evening, as marine layer stratus continues to make a farther intrusion inland than we`ve seen the last couple of nights. The forecast for Friday into Saturday continues to evolve with NWP models struggling with the position of the closed low as it moves on shore. Read details below for highlights on potential for thunderstorms from Santa Cruz south through Big Sur Friday night into early Saturday. && .SHORT TERM... (This evening through Thursday) Issued at 140 PM PDT Wed Apr 23 2025 Satellite shows stratus receding across the interior and portions of the coastline. Confidence is mixed on if coastal areas, such as Half Moon Bay and Monterey, and the SF Bay Shoreline will clear today as stratus continues to feed onshore in those places. The current satellite imagery aligns well with HREF cloud cover guidance which indicated clearing across the interior areas and Santa Cruz Mountains but not for the aforementioned coastal areas and SF Bay Shoreline. The fact that HREF guidance is in agreement with current satellite observations increases confidence that stratus will persist along most of the coast and the SF Bay shoreline through the rest of today. There is a slight chance clearing will happen during the afternoon but any clearing that does occur along the coast is expected to be short-lived before stratus returns tonight. We are starting to see temperatures warming up across the interior with temperatures forecast to peak upper 50s to 60s today. The warmest locations (portions of northern Sonoma and Napa counties and interior southern Monterey County) will reach the upper 60s to low 70s. The marine layer is expected to remain at a similar depth (2500- 3000 ft) again tonight as troughing continues to move into the West Coast. This will result in widespread overcast conditions again with fog likely to develop overnight across the valleys. If you encounter fog on your morning commute, remember to slow down and leave extra time to arrive at your destination as sudden decreases in visibility may be possible. Temperatures will cool down a little more heading into Thursday with highs forecast to be in the mid 50s to mid 60s. Breezy conditions are expected beginning mid to late Thursday morning through early Friday morning. Gusts will generally be between 20 to 30 mph but locally higher gusts between 30-35 mph are possible across elevated terrain (particularly East Bay Hills, Gabilan Range, and Santa Lucia Range). While well below Wind Advisory criteria, it would still be good to secure any loose outdoor decorations tonight before winds pick up tomorrow. && .LONG TERM... (Thursday night through next Tuesday) Issued at 140 PM PDT Wed Apr 23 2025 Thursday night into Friday, upper level troughing will deepen as it continues to move into the West Coast with a cut-off low developing offshore. This cut-off low has continued to shift further south, now moving inland over the Central Coast. An associated surface low and cold front is set to move into the Central Coast overnight Friday into Saturday. As this front approaches, forecast PWAT values increase along the coast of the Central Coast to 0.6"-0.8". The forecasted precipitation totals have increased slightly over the Central Coast with up to 0.5" forecast in the Santa Lucia Range and up to 0.25" across coastal and interior Central Coast. Up to 0.25" is possible across the Santa Cruz Mountains and Santa Clara Hills while the rest of the Bay Area will see up to 0.1". This approaching system will transport in a cooler airmass which will contribute to an increased risk of thunderstorms across the marine environment and Central Coast Friday to Saturday. A 10-15% chance of thunderstorms exists across the marine environment while a 10% chance of thunderstorms exists throughout the Central Coast and Monterey Bay region. Forecast soundings show a few hundred J/kg of CAPE across the Central Coast overnight Friday into Saturday with forecasted CAPE values to peak Saturday morning. To have a thunderstorm you need four main ingredients: moisture, instability, lift, and wind shear (speed or directional). With this system incoming, we have a source of moisture, a source of lift (cold frontal passage), and some instability forecast. The questionable ingredient is wind shear. As of right now during the time of the highest thunderstorm probabilities (5AM-5PM Saturday), forecast soundings show some directional wind shear (winds veering with height indicating some warm air advection is occurring) but not very much speed wind shear. The surface to 500 mb bulk shear shows much higher speed shear values located just to our south in San Luis Obispo County (NWS Los Angeles` CWA). While the current trend for this cut-off low has been to shift southwards, if the low were to shift just slightly northward we could potentially see those higher bulk speed shear values shift into Monterey County. If this were to occur, it would increase confidence that we may see some thunderstorms across southern Monterey County given the alignment of wind shear with our area of moisture, lift, and instability. It`s worth watching over the next few days to see where this cut-off low tracks (further south or further north) and how our thunderstorm risk along the Central Coast changes this weekend. Cooler temperatures in the 50s to low 60s will persist through Sunday before upper level ridging moves back in on Monday. This will kick start a warming trend back to more seasonal temperatures with inland temperatures rising into the 70s and coastal temperatures into the low to mid 60s. Minor HeatRisk, primarily impacting those who are extremely sensitive to heat, is forecast to return to the Bay Area and Central Coast on Monday and Tuesday next week. Long range guidance indicates upper level ridging is likely to persist in the longer term with the CPC outlook showing above normal temperatures and below normal precipitation for the month of May. The rainy season in California typically goes through the end of April with the dry season beginning in May. Our incoming Friday- Saturday system is likely to be one of our last systems of the rainy season before dry summer weather returns. && .AVIATION... (06Z TAFS) Issued at 937 PM PDT Wed Apr 23 2025 MVFR pretty much across the board this evening, pending stratus arrival at KSTS which appears imminent. Deep upper low pressure system approaching the West Coast will increase moisture and onshore flow in the marine layer ahead of its arrival, enhancing stratus coverage further inland and for longer than usual. Expecting MVFR through much of the TAF period with a few hour period of SCT low clouds Thursday afternoon. The approaching system will also act to lift cigs through the period, so should be dealing with cigs a few hundred feet higher in about 24 hours time, as of writing. Some coastal terminals may begin to experience -DZ towards the end of the period as lift within the marine layer increases. Vicinity of SFO...MVFR through the TAF period. There does appear to be a period Thursday afternoon where the lower cloud deck may scatter out enough to result in FEW-SCT, but this is lower confidence. Higher confidence is in thicker lower cloud decks lingering through the afternoon, so included those conditions in TAF. SFO Bridge Approach...Low clouds will linger along the San Mateo Bridge Approach, particularly across the San Francisco Bay from SFO to OAK. Monterey Bay Terminals...MVFR through much of the TAF period with a period of SCT low clouds Thursday midday and afternoon. && .MARINE... (Tonight through next Tuesday) Issued at 838 PM PDT Wed Apr 23 2025 Conditions improve Thursday as winds and seas begin to abate. Quieter conditions to start the weekend outside of some light rain chances over the waters Friday into Saturday. Strong northwesterly breezes and rough seas return late Saturday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 9 PM PDT Thursday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...Behringer MARINE...Behringer Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea

859 FXUS66 KOTX 240503 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1003 PM PDT Wed Apr 23 2025 .KEY MESSAGES... - No significant weather impacts expected for the remainder of this week into the weekend. - Dry weather through Thursday with chances for showers Friday into early next week - Breezy Saturday and Sunday, especially over central WA and near the Blue Mountains. && .SYNOPSIS... Temperatures will trend warmer for the remainder of the week with highs in the 60s today with widespread 70s by Thursday, Friday, and Saturday. Dry weather is expected through Thursday night followed by chances for showers Saturday afternoon and evening, with breezy conditions for Saturday and Sunday. && .DISCUSSION... Today through Saturday: As a ridge begins setting up over the Pacific Northwest coast, it will bring warmer than average temperatures to the area and widespread dry conditions through Saturday. Starting tomorrow, high temperatures will be roughly ten degrees above what is normal for this time of year. This warming in temperatures will last through Saturday, which will see temperatures in the low to mid 70s throughout the valleys. Winds through this period will be light and mostly variable, with breezy gusts to the teens in the Columbia Basin. Minimum relative humidity percentages will be in the high teens and the low 20s. While winds will be mostly calm, these hot and dry conditions could enhance any grass fires that ignite. Saturday through Monday: Late Friday night into Saturday, as a cutoff low makes its way through Northern California, a weak trough will track across northern Washington and bring temperatures down, though they will still be slightly above average. Main impacts with this trough will be gusty winds Saturday afternoon and evening in the Cascades, Waterville Plateau, and the Northeast Blue Mountains. Right now, NBM probabilities have much of the Waterville Plateau seeing a 60-80 percent chance of seeing wind gusts up to 40 mph. Downwind sides of the Cascades and the Northeast Blue Mountains have similar probabilities. Right now, these gusts don`t quite warrant wind headlines, but will keep an eye on them. This trough will also bring chances of rain and thunderstorms to the far southeastern portion of our forecast area, particularly the Northeast Blues and the Lewiston-Clark Valley. Precipitation totals will be light, with less than a tenth of an inch expected. Much of this rain will fall Saturday night into Sunday morning. Surface-based CAPE values of 200- 300 J/kg support thunderstorm formation in these areas as well, though we will have more of an idea once CAMs begin picking up on the thunderstorm potential. Tuesday through Wednesday: As the trough moves out of the area, another ridge will begin setting up, bringing mostly dry conditions and warming temperatures again to the area. Best chances for precipitation during the extended forecast period will be over mountain areas due to orographic lift. /AS && .AVIATION... 06Z TAFS: Widespread VFR conditions and light winds expected through the 24 hr TAF period. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions at TAF sites through the period. && .Preliminary Point Temps/PoPs... Spokane 37 70 43 72 44 73 / 0 0 0 10 10 10 Coeur d`Alene 36 69 42 71 42 71 / 0 0 0 10 10 10 Pullman 36 67 43 70 45 67 / 0 0 0 10 20 20 Lewiston 41 72 45 75 50 73 / 0 0 0 10 20 30 Colville 34 71 38 74 40 75 / 0 0 0 10 10 10 Sandpoint 36 68 40 70 41 70 / 0 0 10 10 10 10 Kellogg 38 65 43 69 46 69 / 0 10 10 10 10 30 Moses Lake 37 74 45 76 47 78 / 0 0 0 10 10 10 Wenatchee 43 71 47 74 51 75 / 0 0 0 10 10 10 Omak 39 73 43 76 45 77 / 0 0 0 10 10 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$

542 FXUS66 KPDT 240541 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR Issued by National Weather Service Spokane WA 1041 PM PDT Wed Apr 23 2025 .UPDATE...Issued Freeze Warnings for the Foothills of the Blues and Lower Columbia Basin in WA from midnight tonight through 9AM Thursday. Low dew points combined with clear skies will create effective radiation cooling to lower temperatures in these areas from the high 20s to low 30s overnight. .AVIATION...06Z TAFs...VFR conditions are expected through the TAF period. Winds will generally be less than 10 kts overnight, and will be around 10 kts or slightly higher during the afternoon into the early evening. && PREV DISCUSSION... /issued Issued by National Weather Service Spokane WA/ SHORT TERM...Today through Friday...Light winds and warm, dry conditions for the rest of today into tomorrow morning as the upper ridge continues moving across the PacNW. With the ongoing northwesterly flow aloft, winds remain locally breezy (15-25 mph) over the Blue Mountain-Foothills extending through central OR this afternoon into evening when they will then decrease. Skies will remain clear as well before cloud coverage increases tomorrow late morning onwards along with locally breezy conditions over the Cascade Gaps until tomorrow evening. The ridge gradually moves east tomorrow evening as a upper trough develops and deepens near the west coast with the shortwave trough moving across the PacNW Friday. Showers will develop at OR Cascades first tomorrow evening but chances are low (<20%). With the southwesterly flow taking over and increased moisture and instability, thunderstorms could develop Friday evening over the Grande Ronde Valley and portions of the Wallowas. However, chances are low (<20%) on their development and extent with CAPE values being relatively low (500 J/Kg or below) and weak moisture content. The soundings for the aforementioned areas were also dry in the lower troposphere as well thus lowering chances on its severity. Chances of showers will increase Friday morning before spreading across most of the forecast area through the day with the Lower Basin, Kittitas and Yakima Valley, and Simcoe Highlands dry. The raw ensembles remain having less than 20% probability for QPF amounts up to 0.10 over the lower part of the East slopes of OR cascades and Ochoco-John Day Highlands, but increases to 30-50% prob Friday night. Winds will remain locally breezy up to 25 mph across the Cascade Gaps as the southwesterly flow aloft persists during the day Friday. High temperatures will continue to be seasonably warm through this forecast period. Feaster/97 LONG TERM...Saturday through Wednesday... Key Messages: 1. Breezy to windy conditions Saturday and Sunday. 2. Rain chances Saturday and Sunday, Thunderstorms possible Saturday. 3. Cooling on Sunday before a warming trend through midweek. The extended period is characterized by an upper level low pressure system to our south and east through the weekend ahead of an incoming upper level ridge that moves over the Pacific Northwest Monday. This will bring elevated winds across the slopes of the Cascades, Gorge, and Blue Mountain foothills, widespread rain across Oregon and cooling temperatures through the weekend. Conditions moderate into the workweek as upper level ridging takes hold, but another weak shortwave may return slight rain chances to our mountain and foothill zones Tuesday. However, the primary concern through the weekend is associated with windy afternoon and evening conditions both Saturday and Sunday. A pressure gradient will develop along the Cascades as a result of the upper level low pressure to our southeast and incoming high pressure along the coast. Sustained west-northwest winds of 20-30 mph with gusts of 35-45 mph will be possible over the aforementioned areas both days. These wind values approach advisory criteria, with the NBM suggesting a 40-60% chance on Saturday and a 50-70% chance on Sunday of wind gusts reaching 45 mph or greater - with the best chance occurring across the Kittitas Valley. Ensembles are in fairly good agreement with the synoptic pattern over the weekend, so confidence in wind advisories being issued over the weekend for these areas is moderate to high (60-80%) - especially on Sunday. The proximity of the upper level low to our south will attribute to enhanced instability across the John Day Basin, Grande Ronde Valley, northern Blue Mountains, and Wallowa County Saturday afternoon and evening with surface CAPE of 150-300 J/kg. These parameters would allow for isolated, discrete thunderstorms to be possible, but current confidence is 25% of occurrence. Light rain is expected to be ongoing across the John Day Basin Saturday morning before extending into Central Oregon, Grande Ronde Valley, northern Blue Mountain foothills, and Wallowa County by mid- afternoon. Light rain is anticipated to continue through the evening and overnight before tapering off Sunday morning. Rain amounts of 0.05-0.15 of an inch are expected over the aforementioned areas. Confidence in these rain amounts is moderate 40-60%, as 59% of ensemble do hint at slightly less rain amounts of 0.03-0.05 of an inch. Flow aloft will be out of the south on Saturday to allow for high temperatures to peak into the low to mid-70s Saturday. North- northwest flow aloft develops Sunday to bring in significantly cooler temperatures Sunday ahead of a slow warming trend through the first half of the week as more westerly flow aloft develops. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 35 73 43 71 / 0 0 10 30 ALW 37 72 46 70 / 0 0 10 30 PSC 34 76 42 75 / 0 0 0 10 YKM 37 73 45 72 / 0 0 10 10 HRI 35 76 43 74 / 0 0 10 20 ELN 36 71 43 68 / 0 0 10 20 RDM 27 72 38 67 / 0 0 10 30 LGD 32 68 38 69 / 0 0 10 30 GCD 30 70 39 69 / 0 0 10 30 DLS 40 75 46 67 / 0 0 10 30 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Freeze Warning until 9 AM PDT Thursday for ORZ507. WA...Freeze Warning until 9 AM PDT Thursday for WAZ028-029. && $$ SHORT TERM...97 LONG TERM....75 AVIATION...77

355 FXUS65 KREV 232038 AFDREV Area Forecast Discussion National Weather Service Reno NV Issued by National Weather Service Elko NV 138 PM PDT Wed Apr 23 2025 .KEY MESSAGES... * Warm, springtime weather prevails through Thursday with showers and thunderstorms possible near the Oregon border this afternoon. * A late season storm will bring periods of mountain snow and valley rain, thunderstorms, gusty winds, and much cooler weather Friday through Sunday. * Warmer and drier weather returns early next week with daily chances of showers and thunderstorms in the afternoons. && .DISCUSSION... A couple more days of warm, springtime weather are in store with daytime highs near 60 and 70s degrees. Latest radar obs reveal that showers are developing within a maturing cumulus field in Lassen and N Washoe County. This area may even see a stray thunderstorm this afternoon before the loss of daytime heating after sunset. Otherwise, dry weather prevails until Friday. A considerable pattern change begins Friday as a compact upper low traverses the western states, ushering in a period of cooler, stormy weather area-wide over the weekend. Mountain snow and valley rain showers, thunderstorms, gusty winds, and abnormally cool temperatures are among the likely outcomes Friday through Sunday, although not one impact seems to be particularly significant. Disruptions to travel in and across the Sierra, and perhaps foothills communities such as Virginia City, will likely serve as the greatest impact as snow levels fall from 7000+ feet to near 5000 feet between Friday and Saturday mornings. Snow begins as early as Friday morning, but it appears that a bulk of the snow will fall Friday night into Saturday with lingering snow showers on Sunday. Snow totals have trended up in latest blended guidance, particularly in the Sierra south of US-50 and higher terrain near the Lyon, Mineral, Mono county intersection where there is a 50-80% of 3-6 along highest peaks between Friday and Sunday. Up to a couple inches is conceivable Saturday morning for lower Sierra communities and along Sierra passes (especially Sonora and Tioga passes), which may result in minor slick roads and travel delays. Its doubtful that travel impacts will be significant and prolonged with the intense sun angle and antecedent warm roadways. Lower western Nevada valleys will likely see periods of light rain with totals up to 0.2 between Friday and Sunday. Locally heavier rain is possible if/where thunderstorms develop Friday and Saturday afternoons. Saturday afternoon features the best chances of thunderstorms (15-25%), especially along and south of the I-80 corridor. Potential thunderstorm impacts include brief downpours/ice pellets, gusty outflows, and occasional lightning. Friday will be the windiest day as most areas have at least a 30% chance of wind gusts exceeding 40 mph. Breezy winds continue over the weekend, so plan on the typical wind impacts to aviation and recreational activities. This weekend will also be much cooler as daytime highs are favored to be in the 40s and 50s, followed by chilly nighttime temperatures in the upper teens to 30s. Hard freezes are possible over the weekend so be sure to protect sensitive vegetation. A warming and drying trend occurs early next week as the upper low departs the region. Well warm back up to seasonal averages by Tuesday with some showers and thunderstorms possible each afternoon. -Salas && .AVIATION... Widespread VFR conditions and breezy afternoon winds (gusts of 20-25 kts) will prevail today and Thursday. Periods of MVFR/IFR conditions, LLWS and mountain wave turbulence, and thunderstorms are possible Friday into the weekend. -Salas && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

416 FXUS66 KSTO 231946 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1246 PM PDT Wed Apr 23 2025 .Discussion... .Synopsis... Chances for afternoon and evening showers are in store into the early weekend with Friday-Saturday as the best days for widespread precipitation and thunderstorm development. A cooling trend with light mountain snow showers on Saturday is expected with minor travel impacts. && .Key Messages... * Today: Last day of warm temps and trending cooler through the rest of the week. Isolated showers and thunderstorms tonight, mainly over Shasta County. -Probability of high temperatures 75 degrees F or higher: 50-85% -10-25% chance of isolated showers or thunderstorms Wednesday and Thursday PM across northern Sacramento Valley and surrounding terrain. * Thursday-Weekend: -Cooling trend with breezy to gusty onshore winds Thursday and Friday PM -Isolated to scattered showers and thunderstorms (10-30%) possible, primarily near the Coast Range & Shasta/Tehama County, becoming widespread Friday afternoon through Saturday -High elevation snow showers possible late Friday & Saturday, with a 40-70% probability of 2 inch or more of snowfall above 5500 feet along Sierra/southern Cascades, 25-55% of 4 inches or more -Lingering mountain showers Sunday, then trending warmer and drier For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing .Changes from previous forecast... * Isolated thunderstorm potential increasing for Thursday-Friday PM * High elevation snowfall potential continues to trend higher Friday afternoon through Saturday evening && .AVIATION... VFR conditions across interior NorCal next 24 hours. South to west winds mostly below 12 kts expected, with gusts up to 15 to 20 kts for the Central Valley after 20Z Thu. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

560 FXUS65 KMSO 231857 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1257 PM MDT Wed Apr 23 2025 .DISCUSSION... KEY MESSAGES: - Isolated to scattered showers across southwest Montana, Lemhi County and north central Idaho through Friday. - Breezy easterly winds Thursday into Friday, causing choppy water on area lakes. - Gradual warming trend continues into Saturday. - Cooler with more widespread precipitation likely Sunday into Monday. Shower activity will remain in place across the southern half of western Montana and north central Idaho (generally along and south of Interstate 90) through Friday. Showers will likely become a bit more widespread in these areas Thursday as a low circulation tracks along the southern Montana/ID/WY borders. Precipitation will taper off significantly to the north, especially across northwest Montana. All areas will see breezy easterly winds develop beginning late tonight and lasting into Friday morning. Widespread gusts 20 to 30 mph will be common, with exposed terrain in northwest Montana seeing gusts up to 35 mph, especially in the evening timeframe on Thursday. Those with outdoor sensitivity to wind may want to monitor the forecast, as well as outdoor recreationalists on area lakes due to expected choppy water conditions. Overall, temperatures will be trending upwards through Saturday, with many locations seeing their warmest temperatures of the week Saturday afternoon. Shower activity will begin to increase Saturday afternoon across north central Idaho and southwest Montana ahead of an approaching trough of low pressure. For the most part, forecast models have continued to trend further south with the main low pressure system for Sunday into Monday. While wet, showery and cooler conditions look likely, the scenarios showing a very wet system are becoming less likely (15 to 20 percent chance). In fact, locations near the northwest Montana/Idaho panhandle border may see very little in the way of precipitation. The higher terrain of southwest Montana and north central Idaho will likely see some snow showers down to roughly 6000 feet by Monday, however impacts down to mountain pass levels look minimal at this time. There is growing confidence in high pressure building into the region by mid next week. While the details of this ridge are still somewhat in question, there is a growing chance for a more prolonged dry and warm period by mid to late next week. && .AVIATION... Surface observations this afternoon reveals a surface low across extreme southwest Montana and southeast Idaho. Given this low, a northerly gradient will remain in place through this evening, with sustained northerly winds of 5-10kts with occasional gusts of 15-20kts across north-south orientated valleys through 24/0300Z. Isolated showers will develop across Lemhi County Idaho in the vicinity of this low from 23/2000Z to 24/0500Z. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

028 FXUS65 KBOI 240224 AFDBOI Area Forecast Discussion National Weather Service Boise ID Issued by National Weather Service Pocatello ID 824 PM MDT Wed Apr 23 2025 .DISCUSSION...An upper trough will continue to move across the area through Thursday. Moisture with the trough is limited, confining the showers to areas along the Nevada border this evening. Shower chances increase to 20-50 percent in central Idaho as the core of the trough shifts to our east, along with a slight chance of afternoon thunderstorms. Elsewhere, dry conditions are favored. Temperatures trend warmer on Thursday with highs approaching 70F in the lower valleys. No updates. && .AVIATION...VFR with mid/high level clouds. Isolated showers near the Nevada border this evening. Surface winds: NW-NE 5-15 kt, becoming variable less than 10 kt late tonight. Winds aloft at 10kft: variable 5-15 kt. KBOI...VFR. Surface winds W-NW up to 10 kt, becoming variable less than 5 kt overnight. && .PREV DISCUSSION... SHORT TERM...Tonight through Friday night...Warm and dry across most of the area into the Thursday ahead of the next upper level trough. Expect showers (30% chance) to develop later this afternoon over the higher terrain near the Nevada border ending by sunset. Instability this afternoon is still limited but there could be enough lift for a few lightning strikes over the higher terrain along the Nevada border. Upper level trough approaches the California coast on Thursday setting up a weak ridge across the region. This will limit shower and thunderstorm potential to the Central Idaho mountains. It will also help boost temperatures into the low 70s in the Treasure Valley. The trough forms a low center by early Friday and begins moving inland across California increasing moisture as well as instability across the region. Widespread showers look to begin across Southeast Oregon Friday morning spreading into Southwest Idaho after sunrise. In general, less than a tenth of inch of rain is expected. Shower lift north of the area by late afternoon with partial clearing along the Idaho/Nevada border. Surface heating looks to be more than sufficient along the Idaho/Nevada border with SBCAPEs of around 800 J/kg and shear around 30 kts to support thunderstorm development should this clearing occur. Thunderstorms look move northward into the Snake Plain and into the Central Idaho Mountains Friday evening. Clouds and cooler temperatures across southeast Oregon would likely limit the thunderstorm threat. Gusty winds, brief heavy rain and small hail is possible with the strongest storms. LONG TERM...Saturday through Wednesday...An upper low will move inland across the Great Basin over the weekend. Precipitable water values of 125-150% of normal will support periods of showers, with thunderstorms also possible (10-20% chance) during the afternoon and evening hours as daytime heating aids weak instability. Shower chances will taper off on Monday as the low moves east. Precipitation chances will be highest across southeast Oregon on Saturday and across the mountains of southwest Idaho on Sunday, but generally range from 40-90% across the area. Temperatures will cool from around 5 degrees above normal on Saturday to near normal on Sunday, although uncertainty in the exact track of the low and precipitation coverage results in lower confidence in the temperature forecast. Light mountain snow accumulations are possible on Sunday as snow levels drop to around 6-7kft MSL. Winds will be breezy from the west to northwest on Sunday and Monday as the low departs. A gradual warming and drying trend will develop late Monday and Tuesday as an upper level ridge builds to our west. A weak trough will bring a low potential (10-30% chance) for showers late Tuesday into Wednesday. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...BW AVIATION.....BW SHORT TERM...JDS LONG TERM....ST

395 FXUS65 KLKN 231922 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1222 PM PDT Wed Apr 23 2025 .SYNOPSIS...Isolated to scattered showers and thunderstorms today and tomorrow before a mostly dry and windy Friday. Wet and much cooler this weekend transitioning to a warming pattern to start next week. && .SHORT TERM...Today and Tomorrow Current radar and satellite data shows showers setting up mainly in southern Elko county. These are largely due to a shortwave upper level trough passing over northern Nevada today. Areas of interest with this system are eastern Elko and White Pine counties and western Humboldt county. CAPE is forecast around 200 to 400 J/kg in these areas along with negative lifted indices. Combined, these factors indicate a favorable environment for the development of some isolated thunderstorms in those areas. Conditions dry out overnight but shower and thunderstorm chances return tomorrow afternoon. High temperatures both days will be in the upper 60s and low 70s, with winds 5 to 10 mph gusting up to 20, although some convective gusts up to 35 mph are possible where thunderstorms develop. Lows will be in the 30s and 40s. .LONG TERM...Friday through next Wednesday An Eastern Pacific upper-level area of low pressure will move southeastward just off the coast of California Friday. Although a few showers, and possibly a thunderstorm, cannot be ruled out in Humboldt and Northern Elko Counties, the story of Friday will be the wind. Strong, south to southwest wind gusts will develop Friday afternoon ahead of the aforementioned storm system. A Wind Advisory may be required for White Pine and Nye Counties Friday afternoon into Friday evening. The cyclone aloft should approach the coast of Central California Friday night, before making landfall Saturday. The upper-level area of low pressure will move northeastward across the Silver State Saturday night and Sunday. This cyclone aloft will enter the Great Basin Sunday night. Periods of precipitation are expected throughout Northern and Central Nevada Saturday morning into Sunday evening. Snow levels will start at around 7,000 feet Saturday morning, before dropping to about 6,000 feet Sunday morning. An inch or two of snow is possible over passes and summits along Highway 50 between Austin and Eureka Saturday morning through Sunday morning. Here are probabilities of one tenth of an inch of rain or more for select locations in Northern and Central Nevada this weekend: Owyhee - 85% Spring Creek - 80% Battle Mountain - 75% Wells - 75% Carlin - 75% Denio - 70% Elko - 65% Winnemucca - 65% McDermitt - 65% Jackpot - 60% A ridge of high pressure will move eastward across Northern and Central Nevada Monday. A trough of low pressure may impact the forecast area Tuesday into next Wednesday. && .AVIATION...Slight chance of thunderstorms in Northeastern White Pine County this afternoon into this evening. Any thunderstorm that does develop should stay north of KELY. Slight chance of thunderstorms in Western Humboldt County this afternoon into this evening. Any thunderstorm that does develop should stay west of KWMC. Southwest wind gusts near 25 knots at KELY and KTPH will abate by 02z this evening. VFR condtions will prevail at all terminals. && .LKN Watches/Warnings/Advisories... None. && $$ 94/87/87