927 FXUS66 KSEW 222217 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 317 PM PDT Thu May 22 2025 .SYNOPSIS...Warmer and drier conditions develop across Western Washington through the end of the week as high pressure builds over the region. A approaching front may bring some showers in the mountains Monday and a slight pause on warmer temperatures, but dry and warm conditions return early next week. Another disturbance approaches again around the middle of next week with lower confidence in the pattern by this time. && .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...Temperatures have warmed into the 60s for much of the interior already this afternoon under mostly sunny skies across much of the region, while some banks of clouds remain along the mountains and extending into the lowlands of Lewis County. With zonal flow in place over the region and light low-level flow, not seeing much change over the next 24 hours or so. Expect another day with primarily sunny skies and temperatures again near normal on Friday. It`s worth noting that some spots with clear skies and light wind could drop into the upper 30s in the typically colder spots, while most of the area will bottom out in the 40s. Looking ahead to Saturday, the heights will rise over the region in response to the upper low dropping from the Gulf of Alaska. This will bring warming across the region with afternoon temperatures into the 70s for the interior. .LONG TERM /SUNDAY THROUGH THURSDAY/...The upper ridge remains in place this weekend, with Sunday likely the warmest day for most Expect temperatures to reach well into the 70s and a few of the warmest spots could even approach 80. With the offshore trough in place and the ridge axis shifting east, there is some potential for increasing southwesterly flow aloft to perhaps bring a focus for some convection near the Cascades late Sunday or early Monday. While the chances for thunderstorms remains somewhat low (around 10%) at this time, those with outdoor plans in the Cascades over the holiday weekend will want to maintain aware of this potential. With the passing disturbance on Monday, expect temperatures to run a few degrees cooler with increasing clouds and a cooler air mass. Another round of higher heights on Tuesday/Wednesday with another ridge building over the area will bring another round of temperatures will into the 70s for the interior as southerly flow aloft settles over the region. Confidence in the details of the forecast break down around midweek with ensemble guidance split between maintaining the high pressure over the region and warmer temperatures to persist and allowing the next front to push through the Pacific Northwest and bring slightly cooler, cloudier conditions with a return of rain chances. && .AVIATION...Flow westerly aloft as the upper-level pattern trends more zonal. For tonight, mostly VFR is in store for terminals but isolated MVFR cigs are possible. A 30-50% chance of cigs below 3,000 ft exists for KHQM, KPWT, and KPAE overnight into Friday morning. Onshore flow keeping surface winds at a westerly component this afternoon between 5-10 kt but winds are to decrease in magnitude tonight. More widespread VFR expected on Friday. KSEA...VFR conditions expected through the TAF period. Winds WNW 5- 10 kt this afternoon before becoming lighter and variable overnight. Cloud coverage will vary throughout the period but again, cigs aren`t expected to be less than 5,000 ft. McMillian && .MARINE...High pressure will maintain into the weekend. A weak disturbance is still on track to dissipate before making it to the coastal waters on Friday. As a result, impacts are unlikely. What we`ll have to watch is diurnal westerlies through the Strait of Juan de Fuca. For tonight, HREF guidance has a 60-80% chance of SCA gusts (21-25 kt) occuring over the central/east strait. This is a marginal situation as gusts appear to be infrequent but we`ll continue to monitor the threat this afternoon-early evening. The next front is currently forecast to arrive on Monday, with high pressure remaining stubborn over the coastal waters shortly afterwards. High pressure may trend into Wednesday as well but of lesser strength. Seas 3-5 ft tonight into Friday. A slight uptick in seas is expected again Saturday night into Sunday, with seas building towards 5-7 ft. Seas then look to persist within this range through the early part of next week. McMillian && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

950 FXUS66 KPQR 222216 AFDPQR Area Forecast Discussion National Weather Service Portland OR 316 PM PDT Thu May 22 2025 .SYNOPSIS...A warming and drying trend takes hold across the region for much of this Memorial Day weekend. More active weather returns late Sunday into Monday, including a 15% chance for Cascade thunderstorms, however, forecast confidence degrades dramatically by Wednesday of next week. && .SHORT TERM...Tonight through Sunday...Radar and satellite imagery shows lingering shower activity has remained fairly isolated this afternoon, primarily confined to the higher terrain of the coast range/Cascades, likely persisting into the evening hours before drier weather returns. Another weak and progressive trough will pass over the region early on Friday with almost all areas remaining dry locally due to a lack of moisture/upper-level forcing. By Friday afternoon, heights aloft will begin to rise in earnest as longwave ridging begins to build over much of the western CONUS. Temperatures jump into the 60s and 70s Friday afternoon which is right around normal. This warming trend continues into Saturday as well with the axis of the amplifying upper-level ridge passing west to east over the Cascades leading to another 5-8 degree jump in high temperatures. Confidence is high for maximum temperatures rising into the mid 70s to near 80 along the I-5 corridor and other inland valleys Saturday afternoon, above normal for late May. Late Sunday chances begin to increase for a brief breakdown in upper ridging as an increasing number of ensemble and deterministic models favor a negatively-tilted shortwave trough undercutting the ridge, before potentially becoming cutoff over California. Given the warm antecedent conditions and advection of a mid- level moisture layer preceding the trough, thunderstorms remain a possibility (15-20%) late Sunday afternoon, mostly near the crests of the Cascades eastward. Models like the GFS/NAM currently show around 200-600 j/kg of MUCAPE in this region but the exact timing of shortwave forcing will determine the extent of convective development; a delay of this feature further into the evening hours would keep activity weaker and pushed to the east. Still, it`s definitely worth paying attention to if you plan on venturing outdoors for the holiday weekend, especially the Cascades. .LONG TERM...Monday through Thursday...Ensemble and deterministic guidance generally depict the axis of the aforementioned upper-level trough with the attendant cut-off low to our south passing overhead on Monday leading to a slight chance for showers in the interior valleys but better probabilities for activity along the coast/coast range and Cascades due to more advantageous orographic forcing. Still, exploring the NBM an other ensemble products overall rainfall accumulation during this period looks rather low, <0.05-0.1" for the Willamette Valley, 0.05-0.2" coast/coast range, and 0.1-0.3" Cascades. Resurgent ridging into Tuesday would then see a quick return to warm and dry weather across the region. Then, confidence rapidly decreases Wednesday and beyond as ensemble spread increases dramatically. Persistent ridging could see a prolonged period of warm to hot temperatures and dry weather continue (50% of ensemble members), while a breakdown of the ridge could instead see a return to cooler and wetter conditions (also ~50% of ensemble members). This has resulted in a nearly 30 degree temperature spread (ranging from 65 to 95 degrees) between the NBM 10th and 90th percentile for the potential high on Wednesday. The current forecast sits in between (upper 70s to mid 80s) with hopefully better model agreement in the coming days increasing forecast confidence. -Schuldt && .AVIATION...Onshore flow will maintain broken to overcast mid level clouds through tonight, with more clearing expected on Friday. As of 20z Thursday, predominately VFR conditions with MVFR CIGs lingering at a few locations. Coastal sites have a 50-60% chance of MVFR CIGs returning around 04-06z Friday. Winds remain onshore and generally less than 10 kt. /DH PDX AND APPROACHES...Predominately VFR conditions expected through the TAF period with broken mid level clouds. Northwest winds expected around 4-6 kts. /DH && .MARINE...Weak high pressure offshore will maintain north to northwesterly breezes across the coastal waters into the weekend. Winds generally remain below 10-15 kt, though inland daytime heating could drive the diurnal strengthening of the pressure gradient, allowing winds to gust up to 20 kt along the nearshore waters. Seas will persist around 3 to 4 ft through Saturday. By early Sunday, winds turn southerly ahead of a weak front, increasing through the day, but expected to remain below 20 kt. A northwest swell will also build seas to around 6 to 7 ft. /DH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

974 FXUS66 KMFR 222102 AFDMFR Area Forecast Discussion National Weather Service Medford OR 202 PM PDT Thu May 22 2025 .DISCUSSION...Generally, westerly flow will continue in the mid-levels throughout the next week, with periodic waves of energy passing over the area every other day or so. This low- impact pattern will keep temperatures near to above normal for this time of year (with a gradual warming trend as the pattern gradually becomes more ridge dominated), and also provide a few periods of shower and thunderstorm chances. An weak upper trough passed over the area early this morning, and is now passing to the east. Arriving too early in the day to take advantage of daytime heating, only a few lingering showers remain along the northern Cascades, and these should taper off and end over the next few hours. Shortwave ridging is now building in and drying the area out, but this will be short lived, as the next weak upper trough arrives tonight into Friday morning. This impulse isn`t expected to have much, if any affect on the weather, other than increased clouds and breezes, and perhaps a few showers or maybe even a lightning strike or two well east of the Cascades tomorrow afternoon. A stronger ridge then builds in for the weekend, with dry conditions across the region on Saturday and Sunday, and temperatures rising to levels more typical of late June or early July. The next upper trough will slowly move east towards the coast late Sunday afternoon, and if it gets close enough before the end of the day, it could trigger a few showers along the coast and an isolated thunderstorm or two in the northern Cascades. Otherwise, most shower activity will be along the northern portions of the forecast area through the overnight and morning hours. By Monday afternoon, the trough will shift to the east, and shower activity will intensify along and eats of the Cascades. With the cooler air aloft, and daytime solar heating in the afternoon, some modest instability is forecast to develop, so some isolated thunderstorms are possible, mainly across Klamath and Lake counties. Any precipitation should dissipate through Monday night as the trough exits to the east. Temperatures will be a little cooler Monday, with clouds and showers helping to keep temperatures right around normal for this time of year. Models are indicating that ridging will then enter the area and remain in place through at least Wednesday or Thursday, keeping the area dry and pushing temperatures back to above normal. Another trough may be lurking just offshore, however, and could enter the area late in the week with another round of showers and cooler temperatures. There is a fairly large spread in the model guidance regarding the timing and strength of the trough and how far inland it will push, so changes and updates regarding this part of the forecast are likely over the next few days. -BPN && .AVIATION...22/18Z TAFs...VFR conditions continue across northern California and southern Oregon this morning. Ceilings over Roseburg are currently just below the MVFR threshold, but these ceilings are not expected to persist very long. Usual afternoon winds are expected, with these winds calming into tonight. North Bend and the Umpqua Valley may see some borderline MVFR ceilings develop late tonight into Friday morning. -TAD && .MARINE....Updated 200 PM Thursday, May 23, 2025...Below advisory seas continue today under stable atmospheric conditions. Northerly winds increase south of Cape Blanco on Friday morning. Wind-built steep seas are forecast south of Port Orford and within 50 nm of shore on Friday afternoon through late Friday night. Below advisory seas return on Saturday. On Sunday, westerly swell increases through the day, peaking Sunday night into Monday morning. Scattered marine showers are also possible early Monday morning, but these should be unimpactful. Stable conditions could return on Monday afternoon and could continue into the middle of next week. -TAD && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. PACIFIC COASTAL WATERS...None. && $$

177 FXUS66 KEKA 221900 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1200 PM PDT Thu May 22 2025 .SYNOPSIS...Upper level disturbances for the rest of this week and weekend will bring cooling temperatures. Another period of warm temperatures and high pressure return this weekend before another chance for light rain Sunday into Monday. && .DISCUSSION...Thursday and Friday broad/weak troughing will drift by to our north, but will not have much more effect than mid level cloud cover and cooler temperatures, especially in interior valleys. The chance of isolated thunder Friday afternoon is becoming less and less likely for eastern Trinity county with minimal moisture available to initiate convection. High amplitude ridging is expected to return Saturday and Sunday, allowing temperatures to briefly rebound into the 70`s and 80`s. Long range models are becoming more confident in another upper trough and surface frontal system clipping the region late Sunday into Monday. NBM indicates 30 to 40% probabilities for >0.01 inches, most likely Monday morning should it occur. This is forecast to be followed by more warming mid next week. && .AVIATION...High pressure will wedge back into Northwest California during this TAF period. This afternoon and into the evening, north to northwesterly winds will pick up at most all area terminals. In southern Mendocino and Lake counties, gusts to 20 knots are likely into this evening. Late this evening and into early Friday, marine stratus is projected to develop under an inversion, mostly around the Humboldt Coast north of Cape Mendocino. There could be southerly reversal winds around the Del Norte Coast which brings the possibility of stratus moving into KCEC. HREF indicates about a 20 to 30 percent chance for MVFR conditions at KCEC by early Friday morning. MVFR conditions are most likely at KACV by early Friday morning; however there is a 50 to 60 percent chance for IFR ceilings and a 25 to 35 percent chance for LIFR ceilings. KUKI is expected to remain VFR. /JLW && .MARINE...Northerly winds will increase again as high pressure builds back over the Pacific throughout today and into Friday. As a result, small craft winds and seas are forecast for the southern waters Friday and Saturday. Another weak system will approach the region over the weekend allowing winds to decrease again and possibly even turn out of the south briefly in the northern waters by Sunday. Northerly winds and steep seas are projected to increase again by the middle of next week as high pressure builds back into the region. /RPA /JLW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM Friday to 3 PM PDT Saturday for PZZ455-475. && $$ 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

114 FXUS66 KMTR 221626 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 926 AM PDT Thu May 22 2025 ...New UPDATE, MARINE... .SYNOPSIS... Issued at 238 AM PDT Thu May 22 2025 Elevated fire weather conditions remain the primary concern today as warm, dry, and windy conditions continue. && .UPDATE... Issued at 926 AM PDT Thu May 22 2025 Fairly clear skies across the region this morning with only a few patchy areas of stratus along the coastline. The Fort Ord Profiler shows the marine layer is around 1,000 ft and is expected to deepen to around 1500 ft tonight. Elevated fire weather concerns continue in areas where grasses are cured due to dry daytime conditions and gusty winds between 25-35 mph. Otherwise, no updates needed. && .SHORT TERM... (Today and tonight) Issued at 238 AM PDT Thu May 22 2025 The marine layer is being observed at 800 feet by the Fort Ord profiler with satellite just starting to show some stratus forming over Tomales Bay and along the San Francisco Peninsula Coast. Despite this, the 00Z KOAK sounding revealed a LowRH (surface-850 mb) value of 25%, a MidRH (850mb-650mb) value of 9%, and a precipitable water value of 0.45 inches which is slightly above the 10th percentile of 0.42 inches for 00Z May 22nd. An upper-level shortwave trough will skirt the region today, bringing temperatures back down to seasonal normals. Of more impact will be the strong onshore winds that it brings with gusts of 25-35 mph expected over the waters, along the immediate coastline, through northwest/southeast oriented valleys, and in the higher terrain. These winds in conjunction with poor relative humidity (both overnight recovery and daytime minimum) will continue to support elevated fire weather conditions. && .LONG TERM... (Friday through Wednesday) Issued at 238 AM PDT Thu May 22 2025 An approaching second, deeper upper-level shortwave trough will deepen the marine layer and finally ease fire weather concerns for the time being as excellent relative humidity recovery (70%+) returns to all but the highest terrain of the Central Coast. Sensibly, temperatures will drop to 5 degrees below normal, dubbing tomorrow the coolest day of the week. Heights will begin to build and temperatures rebound to seasonal normals Saturday as a positively tilted upper-level longwave ridge builds into the West. Due to the orientation of the upper-level pattern, the warmest day for the Bay Area will be Saturday with the Central Coast having to wait until Sunday to achieve that feat. The unofficial start of Summer (Memorial Day) will feel anything but with below normal temperatures brought to you by a dry cold front. The previously mentioned upper-level longwave ridge will build and broaden across the Western two-thirds of CONUS with an upper-level shortwave trough likely to undercut it, resulting in split flow and unimpactful weather for our region Tuesday and Wednesday. && .AVIATION... (12Z TAFS) Issued at 416 AM PDT Thu May 22 2025 VFR is expected to prevail with a dry airmass across our region in place. Local geographic effects are responsible for low stratus in the vicinity of the Monterey Bay terminals. Vicinity of SFO...VFR is expected to persist through the day and evening hours with a chance of MVFR/IFR cigs late in the forecast period for early Friday. Confidence is too low for mentioning in the TAF attm. Gusty onshore winds will develop this afternoon and persist until after midnight. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...MVFR/IFR cigs early this morning due to local effects from an otter eddy in Monterey Bay. Short term guidance suggests that the low stratus will lift after 15z this morning and remain VFR until after midnight, when there is a chance for MVFR/IFR cigs developing in the early morning hours Friday. && .MARINE... (Today through Tuesday) Issued at 926 AM PDT Thu May 22 2025 Widespread hazardous marine conditions continue today as strong northwesterly breezes with near gale to gale force gusts and rough seas persist. Fresh to strong northwesterly breezes and moderate to rough seas will prevail Friday through Monday. && .FIRE WEATHER... Issued at 238 AM PDT Thu May 22 2025 The combination of poor daytime relative humidity of 15-25% and onshore winds with gusts of 25-35 mph along the immediate coastline, in northwest/southeast oriented valleys, and in the higher terrain will continue to support elevated fire weather conditions today. The greatest period of concern is today in cured grass areas. Remain fire wise and do not be the reason for fire starts. Sarment && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Friday for SF Bay N of Bay Bridge. Small Craft Advisory from 3 PM to 9 PM PDT Friday for SF Bay N of Bay Bridge. Gale Warning until 9 PM PDT this evening for Mry Bay. Small Craft Advisory until 9 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Gale Warning from 9 AM Friday to 3 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory until 3 PM PDT Friday for Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning from 3 PM Friday to 3 AM PDT Saturday for Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 0- 10 nm. Gale Warning until 9 PM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...JM MARINE...Murdock 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

071 FXUS66 KOTX 222142 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 242 PM PDT Thu May 22 2025 .KEY MESSAGES... - Warm Memorial Day Weekend with a minor heat risk. Temperatures warming into the 80s Sunday. Water temperatures remain cold. - Widely scattered showers with a 10-30 percent chance of thunderstorms Sunday night into Memorial Day. && .SYNOPSIS... Temperatures will gradually warm through Sunday as high temperatures warm into the 70s and 80s for the weekend. There is growing potential for showers and thunderstorms from Sunday night into Memorial Day. && .DISCUSSION... Tonight through Saturday Night: An upper trough over Eastern WA/N Idaho will exit into NW Montana tonight leading to a decrease trend in shower activity this evening, followed by dry conditions overnight. Afternoon sunbreaks have helped destabilize the atmosphere in the Central Panhandle Mountains where there is a 20% chance of thunderstorms through the early evening. These storms only have near 200 J/KG of CAPE to work with so main impacts will be brief downpours with any storms that develop. Friday begins the warming and drying trend as a large closed low digs off the west coast providing south to southwest flow over the region. Residual moisture and afternoon heating is expected to produce another round of afternoon showers on Friday over the northern mountains and ID Panhandle. Given the lack of forcing these showers will be isolated to widely scattered in nature. On Saturday more significant rising of the upper heights occur as a ridge develops over the area. This will bring more significant warming as high temperatures warm into the mid 70s to low 80s. JW Sunday through Thursday: The warm, dry conditions will continue for Sunday. The region can expect its warmest temperatures with highs in the 80s to low 90s. Ensembles continue to bring a shortwave on Monday. It will mainly bring light rain showers to the Inland Northwest. Instability with the wave could generate an occasional thunderstorm. The best chances for the thunder is along the Canadian border, Southeast WA, and the Lower ID Panhandle. The wave will bring slightly cooler temperatures for Tuesday. It will be short lived. Another ridge will be filling in behind the wave. Temperatures will climb back into the 80s and low 90s for Wednesday. Another wave will bring another round of showers and thunderstorms on Thursday. /JDC && .AVIATION... 18Z TAFS: A weak deformation band across eastern Washington into the Idaho Panhandle this morning into the early afternoon will produce light rain for KGEG/KSFF/KCOE. The boundary layer is starting out dry and the incoming rain won`t do much to moisten it up with ceilings anticipate to only drop down to between 4-6 kft AGL and VFR conditions prevailing. Although winds will be fairly light today up to 7-10 kts, there will be a wind shift of northeasterly to westerly between 18-20Z with the passage of a low to the south. Showers will continue to be prevalent closer to the low in the afternoon with isolated thunderstorms south and east of KLWS. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence in VFR conditions today. Chances for enough moisture to produce lower ceilings for MVFR conditions at KPUW/KGEG/KSFF/KCOE remain at a 10% chance. There is high confidence that thunderstorms this afternoon will remain south and east of KLWS with less than a 10% chance for thunderstorms developing at the terminal. JW ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .Preliminary Point Temps/PoPs... Spokane 41 68 44 74 48 83 / 20 10 0 0 0 0 Coeur d`Alene 42 68 44 74 47 83 / 20 10 0 0 0 0 Pullman 39 66 42 73 47 80 / 10 10 0 0 0 0 Lewiston 47 74 49 80 52 88 / 10 10 0 0 0 0 Colville 36 69 39 75 42 83 / 10 20 0 0 0 0 Sandpoint 42 68 43 74 46 82 / 30 20 0 0 0 0 Kellogg 44 65 46 73 49 82 / 30 10 0 0 0 0 Moses Lake 44 76 46 81 50 88 / 0 0 0 0 0 0 Wenatchee 47 76 50 80 55 86 / 0 0 0 0 0 0 Omak 43 75 46 80 50 85 / 10 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$

057 FXUS66 KPDT 222141 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 241 PM PDT Thu May 22 2025 .SHORT TERM...today through Saturday...Radar shows the line of showers that passed through the CWA earlier today has mostly dissipated and is heading off east towards Idaho. A few showers remain possible across the Blues and parts of the WA Cascades as we head through the rest of the night. A stray lightning or two from a shower is possible across parts of the Wallowas later this afternoon. Yakima/Ellensburg have slight chances (15-25% chance) to see an isolated thunderstorm as clouds cleared out from earlier in the day, allowing for some additional instability to re-enter the atmosphere. As the shortwave exits the region, precip chances and sky cover decrease headed into Friday. High temperatures across the board Friday rise to the low 70s to mid 70s. Higher elevations will see low 60s as their high. A secondary shortwave develops later into Friday just south of the CWA, but some moisture advection will make it`s way into the southern parts of the region. Coupled with daytime heating with highs in the high 60s and low 70s and moisture entering southern parts of the CWA, there`s a slight chance (15-25% chance) for an isolated thunderstorm to pop-up in the Southern Blues and eastern mountains Friday afternoon. Ridging will return Saturday and into Sunday morning. The ridge axis will be placed over the region late Saturday morning/early after- noon. By nature, this pattern will set-up for a clear, hotter profile heading into the holiday weekend. Highs will depart 5-15 degrees above the normal for this time of year on Saturday, starting the weekend in the mid to low 80s across parts of the Basin and high 70s across higher elevation areas. Winds will remain light with diurnals patterns, with sustained up to 15 knots. .LONG TERM...Sunday through Wednesday... Key Messages: 1. Isolated thunderstorms Sunday and Monday. 2. Breezy winds Monday afternoon and evening. 3. Thunderstorm chances return Wednesday afternoon and evening. The extended period is characterized by an upper level trough passing through the Pacific Northwest Sunday and Monday before upper level ridging builds through the midweek. The late weekend trough will bring with it periods of light rain across the area Sunday evening through Monday evening as rain amounts of up to 0.10" will be possible for elevations below 4000 feet, and 0.15-0.25" of rain for elevations above 4000 feet. The primary concern associated with this incoming trough will be the potential for isolated thunderstorms as the trough erodes the backside of the retreating ridge of high pressure. CAPE values of 150-250 J/kg are present along the east slopes of the Cascades and across Central Oregon Saturday and from Central Oregon through northeast Oregon on Sunday. Ensembles depict variability on both the incoming trough and present ridge strength, relating to 76% of ensemble members suggesting similar or slightly more CAPE values with 55% of members suggesting an additional 100-300 J/kg Sunday. This suggests that there is slightly more confidence in increasing thunderstorm potential on Sunday afternoon and evening, predominately after 5 PM. Members also suggest that the best probability of increased CAPE would be over the east slopes of the Oregon Cascades extending east through Deschutes and Crook Counties on Sunday. 55% of ensemble members for Monday`s potential for thunderstorms suggest an additional 50-200 J/kg of CAPE than what is currently forecast. However, only 19% of members suggest more than the 50 J/kg increase, which is based on a much stronger upper level trough developing and eroding the ridge. The main hazards associated with these storms will be gusty/erratic winds and the potential for small, pea-sized hail. The incoming trough and the associated cold front will allow for a pressure gradient to develop along the Cascades to allow for breezy winds along the east slopes of the Cascades, Kittitas Valley, Simcoe Highlands, Eastern Gorge, and the Southern Blue Mountains/foothills. Sustained west-northwest winds of 15 to 25 mph with gusts of up to 35 mph will be possible, peaking between 4-9 PM Monday. Confidence in these wind values is moderate (50-60%) as the GFS suggests a pressure gradient of 9-10 mb between Portland and Spokane (PDX-GEG), which is below the normal wind advisory threshold of 12 mb. Ensemble clusters are also split as 53% of members hint at slightly higher winds than what is currently forecast in relation to a stronger incoming trough. At this time, there is low confidence (20-30%) in wind gusts reaching advisory-level (45 mph or greater). Long-range guidance struggles with the weather pattern after Monday, either exiting the trough to our east or dropping it to our south as a closed low pressure system. Either way, it does allow for upper level ridging to occur across the Pacific Northwest, but how much ridging is able to develop will be a result from which solution ends up panning out. The dropping closed low scenario poses the best chance for isolated thunderstorms to occur across the John-Day Basin/Highlands, Southern/Northern Blue Mountains, and Wallowa/Union Counties Wednesday afternoon and evening as around 500 J/kg (ECMWF) of CAPE would be present versus 200 J/kg (GFS) with the eastward departure scenario. Currently, 58% of ensemble members are suggesting near or slightly more CAPE available across the aforementioned areas, which would align slightly more with the closed low scenario. Hazards will be similar to the thunderstorms Sunday and Monday, with gusty/erratic winds and small (pea-sized) hail being the primarily concern. 75 && .AVIATION...18Z TAFS...VFR conditions currently at all sites, with the exception of KRDM which is experiencing MVFR conditions due to reduced ceilings of 15-25kft. These ceilings will improve shortly as VFR conditions persist for all sites through the remainder of the period. Light rain is expected to occur late this morning over KALW, with dry conditions across all terminals through the day. Winds at KRDM and KBDN will be breezy with gusts between 15-20kts this afternoon, but will stay below 10 kts elsewhere. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 45 74 46 81 / 0 0 0 0 ALW 47 73 49 80 / 0 0 0 0 PSC 45 78 45 84 / 0 0 0 0 YKM 45 77 47 82 / 0 0 0 0 HRI 47 78 46 84 / 0 0 0 0 ELN 45 74 45 81 / 0 0 0 0 RDM 37 73 39 83 / 0 0 0 0 LGD 40 70 41 77 / 10 10 0 0 GCD 39 71 41 80 / 10 20 10 0 DLS 47 75 46 84 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...95 LONG TERM....75 AVIATION...75

677 FXUS65 KREV 222057 AFDREV Area Forecast Discussion National Weather Service Reno NV 157 PM PDT Thu May 22 2025 .KEY MESSAGES... * Gusty winds will produce recreation and fire weather concerns into this evening, with dry and breezy conditions also expected Friday. * Near average temperatures will continue through Friday as weak weather systems brush by to the north. * The holiday weekend continues to favor warm and dry conditions, however, be aware of fast and cold rivers and streams due to continued high Sierra snowmelt. && .DISCUSSION... Today`s trough passage across Oregon-Idaho has produced its anticipated winds across eastern CA and western NV, with gusts 30-40 mph in many locations and around 45 mph for a few wind- prone sites near US-395. Sierra crest ridge gusts peaked near 85 mph earlier today. These winds and associated impacts for lake recreation and travel for high profile vehicles will continue through the remainder of the afternoon, then decrease this evening. Another weak trough passage is on tap for Friday, but it will produce less wind with gusts mainly 30 mph or less. Although this system will have limited moisture, a small area of upper level forcing and instability with this trough could produce a few showers and possibly a stray thunderstorm for areas near the OR border Friday afternoon (10-15% chance). Little or no rainfall is anticipated with any showers that form, which will move at a relatively fast pace. The holiday weekend looks to be warm and dry overall, as a high pressure ridge moves across CA-NV. Afternoon cumulus buildups are likely for both Saturday and Sunday with the warmer air mass in place, but potential for showers/thunder is quite low, only about 5% chance. By Memorial Day, a weak trough passage could produce a few late day showers in areas near the OR border, although this potential is also rather low (about 10-20% chance). Sunday is still expected to be the warmest day of the weekend, with highs pushing the upper 80s to near 90 for western NV valleys and 70s for Sierra communities. The other weekend days won`t be quite as warm but still above late May averages. Winds will be lightest on Saturday, followed by zephyr-type breezes Sunday-Monday. Rivers and streams will look appetizing to cool off in, but they will be running fast and cold due to high Sierra snowmelt. Even limited water exposure can pose the risk of hypothermia. Stay safe this weekend! The warm pattern continues next week with highs in the mid 80s-near 90 for western NV valleys by midweek. Dry conditions are again the prevailing scenario, although a few simulations keep a remnant of Monday`s trough around the northern Great Basin for a couple more days, with low 10-20% shower chances persisting for sites near the OR border. MJD && .AVIATION... Widespread VFR conditions prevail through this weekend. Peak wind gusts of 30-35 kts at the main terminals with FL100 gusts to 60 kts continue through early this evening, resulting in mountain wave turbulence and periods of LLWS. Winds Friday will be lighter with gusts near 20 kts followed by even less wind for Saturday, then typical zephyr-type breezes return for the rest of the holiday weekend. MJD && .FIRE WEATHER... Very dry air mass has settled across the region from I-80 southward with minimum RH values in the single digits to lower teens--even as low as 4% at Hawthorne. Wind gusts have generally been in the 30-40 mph range, and these dry and windy conditions will continue until early this evening, resulting in elevated to locally critical fire weather conditions. These elevated conditions retreat Friday and into the weekend as gusty winds subside. However, dry conditions will remain in place with minimum RH between 8-16% for much of western NV southward to eastern Mono County, and 15-25% for the eastern Sierra, Tahoe basin and northeast CA/far northwest NV. Therefore, anyone celebrating the holiday outdoors this weekend should use extra caution with activities that may cause fires. This includes camp fires, sparklers, dragging trailer chains, and target shooting. MJD && .REV Watches/Warnings/Advisories... NV...Lake Wind Advisory until 8 PM PDT this evening NVZ002-004. CA...Lake Wind Advisory until 8 PM PDT this evening CAZ072. && $$

111 FXUS66 KSTO 222036 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 136 PM PDT Thu May 22 2025 .Discussion... .Synopsis... Dry and periodically breezy weather expected from today into early next week with temperatures fluctuating between near and slightly above normal as a more progressive pattern sets up aloft. Elevated fire weather conditions anticipated during breezier periods as low humidity and marginal recovery persists. && .Key Messages... * Today - Saturday: -Quick moving, dry shortwaves bring periods of breezy to briefly gusty onshore winds. -Probability of South-Southwest Wind Gusts > 30 mph: --40-70%, highest across Delta and vicinity area --Strongest winds expected during afternoon/evening hours today. -Marginal humidity recovery expected in onshore flow, but elevated fire weather conditions persist, especially during periods of strongest winds. -Temperatures to fluctuate around near to slightly above normal, with areas of Minor HeatRisk. * Sunday - Thursday: -Stronger weather system to progress toward interior NorCal Sun- Mon, then remain largely stationary over the West Coast into next week. -Primarily dry weather anticipated, although a slight 5-10% chance of isolated showers/thunderstorms possible each day. Highest probabilities over the N. Sacramento Valley and Sierra. -Breezier onshore winds expected, especially Sunday as the system arrives. Probability of South-Southwest Wind Gusts > 30 mph: --60-90% across the Valley and Delta on Sunday -Marginal humidity recovery and elevated fire weather conditions likely to persist, especially during stronger winds on Sunday. .Changes from previous forecast... -Low precipitation chances possible into next week, although forecast uncertainty remains high at this time. -Ensemble guidance indicates a more robust warming trend by late next week. && .AVIATION... VFR conditions expected to prevail next 24 hours. Wind gusts 15-20 kts through 06z Friday across the Delta (westerly gusts), southern Sacramento Valley (southwesterly gusts) and the northern San Joaquin Valley (northwesterly gusts). Breezy westerly wind gusts vicinity Delta after 06z Friday. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

493 FXUS65 KMSO 221832 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1232 PM MDT Thu May 22 2025 .DISCUSSION... KEY MESSAGES: - Cool and showery conditions through Friday morning - High pressure will build this weekend - Low pressure on Monday-Tuesday will bring chances for thunderstorms A trough of low pressure is moving through the Northern Rockies this afternoon, bringing widespread rain showers. The primary circulation of the low will be over north-central Idaho. Idaho and Lemhi counties, as well as southwest Montana, will see the most rain as twenty-four hour precipitation totals will range from about 0.20 to 0.70 inches by Friday morning. Snow levels stay above about 7000 - 8000 feet. Showery conditions will persist on Friday, with the focus of precipitation being in the higher terrain, especially along the Continental Divide. High pressure will build for the weekend. Daytime high temperatures will climb into the 70s for the valleys of western Montana and the 80s for the lower Salmon and Clearwater valleys in Idaho. Sunday and Monday will be about 10 degrees warmer than Saturday. While the ridge amplifies over the Northern Rockies, a trough will dig along the West Coast. Low pressure and an associated cold front will arrive by Monday evening. Southwesterly flow aloft, along with daytime heating, Pacific moisture, and the cold front, will be a good recipe for some afternoon/evening thunderstorms on Monday. Precipitation will be favored south of about I-90 and along the Divide on Monday. A shift to more westerly flow aloft with some embedded moisture will keep showers and thunderstorms in the forecast into midweek. && .AVIATION...A shortwave trough is moving through the Northern Rockies this afternoon. Expect brief reductions in ceiling and visibility under intermittent rain showers into early Friday morning. There will be chances for thunderstorms south of about Interstate 90 (including KMSO) this afternoon after about 22/2000Z. Chances for thunder are about 20-30 percent for KSMN and KBTM, and about 20 percent for KMSO. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

098 FXUS65 KBOI 222029 AFDBOI Area Forecast Discussion National Weather Service Boise ID 229 PM MDT Thu May 22 2025 .SHORT TERM...Tonight through Saturday night...Afternoon showers and thunderstorms over e-central Oregon and w-central Idaho will diminish this evening. Outflow wind gust threat is 40 MPH for the remainder of today. Gusty large-scale winds will continue to gust 30-40 mph across s-central Idaho zones early this evening, tapering off towards sunset. Tonight is dry as the first of two shortwave troughs lifts into MT. The second trough will enter the region on Friday elongating as it moves through the Intermountain West. Elevated terrain will see a 20-40% chance of afternoon showers and thunderstorms Friday. The outflow wind potential from showers/storms on Friday will again reach 40 MPH. The Snake Plain will remain dry as conditions remain too stable for development. Memorial Day Weekend will start off dry as an upper ridge builds along the Cascades on Saturday. High temperatures will warm 3-8 degrees from Friday to Saturday with lower elevations closing in on 80F and mtn valleys nearing 70F, or about 5 degrees above normal. .LONG TERM...Sunday through Thursday...A narrow, amplified ridge will move overhead on Sunday, boosting temperatures to 10-15 degrees above normal with dry, calmer conditions. A weakening Pacific trough will approach late Sunday and increase the chance for showers and thunderstorms by Monday afternoon, but temperatures will only lower by a few degrees as the trough moves overhead. The trough will continue east on Tuesday, and a chance of showers/thunderstorms will remain over central Idaho on the backside of the trough. Models fall out of agreement on timing and evolution, however, so forecast confidence for temperatures and storms remains somewhat low. High pressure will begin to build for mid-week, though lingering mid- level moisture and increased daytime instability should re-introduce showers and thunderstorms over the higher terrain. Currently, Wednesday is forecast to be the hottest day of the week before the next Pacific trough arrives Thursday. && .AVIATION...Generally VFR. Isolated showers and thunderstorms this afternoon, ending by sunset. Localized MVFR/obscuration in mountains. Gusts up to 35 kt with storm outflows. Surface winds: W to N 5-15 kt with gusts to 20-25 kt, except 15-25 kt with gusts to 30-35 kt for MUO-KGNG-KJER area. Winds aloft at 10kft MSL: W 10-25 kt. KBOI...VFR. A 20% chance of thunderstorms hitting the terminal this afternoon. Erratic outflow gusts to 25-35 kt with storms. Winds outside of storms: NW-N 10-15 kt, gusts to 15-25 kt. Weekend Outlook...Generally VFR. Isolated showers and thunderstorms Friday afternoon, with outflow gusts to 25-35 kt. Mountain obscuration in precip. VFR and mostly clear Sat/Sun. Winds: W to NW 5-15 kt with 20-25 kt gusts on Fri/Sat, then generally E to S 5-10 kt Sun. && .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 SHORT TERM...DG LONG TERM....SH AVIATION.....SH

192 FXUS65 KLKN 222150 AFDLKN Area Forecast Discussion National Weather Service Elko NV 250 PM PDT Thu May 22 2025 .KEY MESSAGES... * A warming trend is expected through the weekend and into next week. * Mostly dry weather for the next several days. * A 15-25% chance of showers and a 15% chance for thunderstorms along the ID/NV border Friday afternoon and evening. * A 15-25% chance of showers and 10-15% chance for thunderstorms across portions of eastern Nevada Saturday afternoon and evening. && .DISCUSSION... Issued at 248 PM PDT Thu May 22 2025 WEATHER PATTERN OVERVIEW: Satellite this afternoon is showing mainly sunny skies at this time with a few mid-clouds over far northern Nevada, along the border with Idaho. No precipitation is noted on radar at this time. Look for mainly clear conditions tonight with lows in the 40s. All models have been consistent in showing a shortwave trough in the mid to upper levels for Friday. This feature is expected to bring a fifteen to twenty-five percent chance for showers and roughly a fifteen percent chance for thunderstorms well north of I-80and along the border with Idaho. Not much in the way of precipitation is expected. Winds will be breezy with speeds of about 20 to 25 mph. Highs will be in the 70s and 80s. Clearing and rather mild conditions expected for Friday night with lows in the 40s and 50s. Warming trend continues to build over the weekend and into next week with temperatures well above into the 80s and 90s. An off-cut low pressure system over the Great Basin area brings in some moisture Saturday, however there is very low confidence that it will bring in precipitable moisture. Only chance for light amount of rain will be over White Pine County with a less than 20% chance. Sunday, the upper level trough will dissipate with strong upper ridging moving over the state, keeping weather activity dry and sunny throughout much of central and northern Nevada, however active weather across northwestern U.S. could bring in some isolated thunderstorms along the northern state border with chances for activity remaining below 20% across the week. The dry dominant warming trend (with small chance of thunderstorms along the northern state border) is expected to last throughout the week. Breezy southerly/southwesterly winds in the afternoon Monday and Tuesday at 10-15 mph, then shifting to a more westerly direction Wednesday afternoon at 10-15 mph. FORECAST CONFIDENCE & DEVIATIONS: NBM has been fairly consistent with the strength and timing of the next upper level feature for Friday and Saturday, along with the warming temperatures through the weekend. No changes were made to the forecast. && .AVIATION... (00Z TAFS) VFR conditions expected at all terminals over the next 24 hour period. Zonal flow pattern over the state will aid in increasing winds over all terminals from a westerly direction and shifting from a northerly direction this afternoon with speeds up to 15-20 kts, gusts 25-30kts. Late afternoon to evening winds are expected to dissipate below 10 kts except at KTPH staying breezy above 10 kts. && .FIRE WEATHER... An upper level wave traversing the area Friday will bring isolated to scattered showers and isolated thunderstorms to the far northern sections of fire zones 437, 438, 469 and 470. Not much in the way of rainfall is expected and areal coverage is expected to be limited to locales north of I-80. Another round of isolated activity is possible in central Nevada Saturday with little to no accumulations expected. Afternoon high temperatures will be increasing to above normal conditions by Sunday with mid to upper 80s by early next week. && .LKN WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...86 AVIATION...97 FIRE WEATHER...86