Graphical Hydro Meteorological Discussion

833
FXAK68 PAFC 220054
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
454 PM AKDT Sat Jun 21 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

Discussion:

Hot, dry, windy conditions continue this afternoon in the Copper
River Basin, where a red flag warning remains in effect until 10
PM AKST this evening. A pattern change is on the horizon as an
upper level ridge continues to move east into Canada, allowing a
large low in the southern Bering to increase southerly flow into
Southcentral. This will bring several shortwave troughs up
through the Gulf. Model agreement remains poor to moderate
concerning the timing and strength of these waves, however,
southerly flow will increase cloud cover, lower temperatures
slightly, raise the relative humidity, and improve air quality by
evacuating residual haze of the past several days.

The NAM and ECMWF are most in agreement that Light rain will
start this afternoon across the eastern Kenai Peninsula and
continue through Sunday. By early Monday morning, southeasterly
flow brings rain into Cordova, Valdez, and potentially the Copper
River Basin with lower chances (due to downsloping) for the
Anchorage bowl and MatSu regions by the afternoon. A second wave
also sweeps across Kodiak late Monday, which intensifies and moves
north into Cook Inlet by Tuesday morning.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Tuesday night)...

An upper level low spinning just north of the Central Aleutians
is becoming vertically stacked with a nearby 996 mb surface low.
Although the surface low has reached maturity and has begun to
occlude, foggy and misty conditions will continue through the
weekend for the Pribilof Islands.

Onshore flow for coastal and parts of the mainland Southwest is
causing areas of light rain for the Kuskokwim Delta. Fire danger
levels are trending down for the short term due to light rain and
cloud cover, although chances for wetting rain (0.1 inches in a 12
hour period) remain low. Temperatures will remain on the cooler
side across Southwest due to the southerly flow off of the Bering
Sea. Southeast winds through Kamishak Gap into Interior Bristol
Bay and the Kuskokwim Valley will begin to diminish early this
evening into the overnight hours. A warming trend will begin into
the new work week as low-level to mid-level flow becomes more
southeasterly Monday and into Tuesday. Clouds and showers will
linger with upper level shortwaves lifting across the area from
the North Pacific and Bering Sea.

Farther west, gusty southeast winds continue across the southern
Alaska Peninsula (AKPEN), especially through Cold Bay, through
Sunday evening before winds slowly begin to relax. Gusts should
peak up to 45 mph this afternoon and evening. Showery conditions
will also persist through the weekend and into the new work week
across the southern AKPEN with low cloud ceilings and off and on
showers across the Eastern Aleutians. Another front works eastward
from Kamchatka Sunday morning to over the western Bering and
Western Aleutians by Sunday evening. Southerly gale-force winds
are expected to accompany this front across the Western Aleutians
before it quickly begins to fall apart and its winds weaken to
small craft as it reaches the Central Aleutians Monday and the
Eastern Aleutians, Pribilof Islands, and southern AKPEN Tuesday.
The heaviest rain is expected to be confined across the western
Bering and Western Aleutians Sunday evening with light to moderate
rain across the Central Aleutians Monday and light rain across
the Eastern Aleutians, Pribilofs Islands, and southern AKPEN for
Tuesday. What is left of the front will merge with the remnants of
the aforementioned occluded low/trough heading into Tuesday.

-DN/AM

&&


.LONG TERM FORECAST (Days 4 through 7: Wednesday through Saturday)...

We are beginning to get a little more motion in the weather
systems across the Alaska region through the forecast period. A
closed upper level low over the Central Bering begins its trek
across the Alaska Peninsula into the Gulf of Alaska by the
weekend. Several shortwaves rotating through the pattern help
accelerate its movement, and help set up some Easterly wave
conditions across Southcentral Alaska. The upper level ridge
across the Northern portions of Mainland Alaska drift into the
Arctic through Saturday. Forecast guidance begins with a
deterministic blend of GFS / ECMWF and Canadian models that
diverge early in the period, so a change to ensemble means will
carry the large scale features through the rest of the forecasts.

Diminishing warmer temperatures over Interior Alaska helps draw
down the possibilities of convective activity across the Central
Alaska, with the last of the showers and thunderstorms occurring
in the Eastern border zones. A slowly weakening surface low near
the Pribilofs slips across the AKPEN into the Central Gulf of
Alaska by the weekend. Windy conditions close to gale force slips
over the Western and Central Aleutians for Wednesday. Gusty winds
cross the Central Aleutians late Thursday into early Friday.
Widespread rain over the Eastern Bering moves over Southwest
Alaska, AKPEN and Kodiak Island through Friday and spread along
the Southcentral coast through Saturday. Gusty Easterly winds set
up over the Northern Gulf of Alaska late Friday into Saturday. A
moderately strong North Pacific low approaches the Western
Aleutians with rain for Friday before heading back into the North
Pacific for Saturday.

- Kutz

&&

.AVIATION...

PANC...VFR conditions will persist. Southeast winds developing
along the Turnagain Arm may bend into the terminal this evening,
with occasional gusts up to 25 kts. However, there is still a
chance these Turnagain Arm winds don;t bend toward the north
enough to move over the terminal which would keep westerly winds
prevalent as they are the result of the eddy shearing off the
core of stronger Turnagain winds. Either way, the winds will
slowly diminish and become more southerly overnight into early
Sunday morning.

&&


$$

857
FXAK69 PAFG 212117
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
117 PM AKDT Sat Jun 21 2025

.SYNOPSIS...The ridge of high pressure aloft continues to slowly
break down with cooling today through Monday before more dramatic
cooling on Tuesday as a low from Bristol Bay undercuts the ridge
in the Gulf of Alaska. Thunderstorm activity will shift north this
afternoon and evening to the Brooks Range before diminishing
Sunday. Increasing showers, humidity, and moisture across the
Interior on Monday. The West Coast will maintain mostly light
winds while east winds increase to 20 to 25 mph across the Arctic
Coast Monday through Wednesday.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
- A cooling trend over the next several days. Highs mainly in the
70s but cooling into the 60s early next week.

- Widely scattered thunderstorms are expected over the Eastern
Interior but becoming more isolated as temperatures cool.

- South winds through Alaska Range Passes will gust to 40 mph
today. A Red Flag Warning for gusty south winds...low humidities
and dry fuels south of Delta Junction.

West Coast and Western Interior...
- A cooling trend over the next several days. Highs mainly in the
70s but cooling into the 60s early next week.

- Isolated thunderstorms this afternoon in the north, except
scattered storms from Hughes northeast to Ambler and Shungnak
and north to the south slopes of the Brooks Range. No
thunderstorms expected Sunday.

North Slope and Brooks Range...
- Scattered thunderstorms developing throughout the region today
into Sunday. Focus for storms Sunday will be the central and
eastern Brooks Range. Any storm can come with frequent
lightning, heavy rain and strong gusty winds.

- Temperatures remain warm through the weekend and into next week.

- Generally northeast winds around 10 mph. East winds increase to
15 to 25 mph from Utqiagvik eastward on Monday and persist
through Tuesday.

&&

.FORECAST ANALYSIS AND DISCUSSION...Bering Sea low pressure system
is pushing a moist southerly flow over southwest and southcentral
Alaska today. Shortwave energy will move up into the northern
Interior and Brooks Range and be the statewide focus for today`s
thunderstorm activity. The Yukon Uplands and White Mountains
should continue to see isolated storms today. Confidence is high
this low will bring several days of cooler - more seasonable
weather to the southern Interior.

Sunday convection will be focused from the Central Brooks Range
southeast to the Yukon Uplands - roughly along a line from Utqiagvik
to Eagle. Across the western and central Interior more stable
conditions should exist as cloud cover and rain showers move up
from the south.

&&

.FIRE WEATHER...A Red Flag Warning has been issued for the Delta
Junction area this afternoon for hot, dry, and windy conditions as
south winds gust to 35 mph through the Alaska Range passes. The
focus for thunderstorm activity moves northwest today to be from
Hughes to Shungnak to Ambler and north to Howard Pass as a
shortwave trough that brought scattered thunderstorms near Galena
yesterday continues to move northward. There will also be widely
scattered thunderstorms across the entire Brooks Range as
southerly upslope flow helps initiate thunderstorm activity there.
Thunderstorms across the rest of the Interior and North Slope
will be isolated. On Sunday, thunderstorm activity further
decreases with just widely scattered storms over the Central and
Eastern Brooks Range and isolated storms north and east of
Northway to Fairbanks to Howard Pass. Temperatures cool on Monday
and significantly on Tuesday as a low undercuts the ridge to the
east. Should see highs mainly in the 60s by Tuesday across the
Interior with increasing showers and humidity. This looks to last
through at least Thursday before a modest warm up next weekend.
Widely scattered thunderstorm activity is still expected across
much of the Interior on Monday.

&&

.HYDROLOGY...We are observing water levels dropping for all
the North Slope rivers as snowmelt ceases. All remaining
advisories have been cancelled. Expect steady rises along all of
the Tanana River as hot temperatures have caused an increase in
glacial and snow melt near the headwaters. Will be keeping an eye
on this next week as precipitation begins to increase across the
basin as well. The current forecast brings the Tanana at Fairbanks
to within about a foot of action stage by late Monday night. Small
streams may see quick rises near where thunderstorms drop heavy
rain today along the south slopes of the Brooks Range. Otherwise
there are no concerns.

&&

.EXTENDED FORECAST DAYS 4-7...The upper ridge is expected to
remain over northeast Alaska and the Canadian Yukon with the Bering
Sea Low energy undercutting it across southern Alaska. Cooler, more
seasonable temperatures with reduced thunderstorm activity will
occur across much of the Interior of Alaska Monday and Tuesday. We
should see scattered to widespread rain showers as well. As the week
progresses a southeasterly flow will return as a Low pressure system
moves into the Gulf of Alaska. Temperatures and thunderstorm
activity will begin to increase again across the Interior Wednesday
into late next week.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Red Flag Warning for AKZ937.
PK...None.
&&

$$

Chriest/Maier

755
FXAK67 PAJK 220549
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
949 PM AKDT Sat Jun 21 2025

.UPDATE...Aviation discussion update for 6z TAF issuance.

&&

.SHORT TERM.../through Sunday night/...
A pattern change is coming to SE AK. The ridge of high pressure
that brought the dry and warm weather will slide southeast and be
replaced by a trough tomorrow. This switch means one more warm day
before clouds return late tomorrow and rain chances return to the
forecast early next week.

Key Messages:
-Sunday will be another warmer-than-normal day with afternoon
temps in the upper 60s to 70s.
-Isolated spots reaching 80 degrees still likely for the Haines
Highway and Hyder.
-Cooler temps along the coast due to the marine layer.
-Clouds move in from the west late tomorrow and tomorrow night.
-General lights winds expected except for areas that usually
experience sea breezes.

Details:
It`s been another warm day in SE with most areas seeing afternoon
temps above normal for this time of year. Tomorrow will be one
more warm day before cooler, more normal temps return early next
week.

The ridge of high pressure begins to break down tomorrow as a
trough of low pressure pushes into the gulf from the west. This
will push the ridge southeast. This pattern change means clouds
return late Sunday into Sunday night.

Land wind speeds will be very similar to what we`ve been seeing
lately. Any increased speeds or changes in direction will be due
to sea breezes in the afternoon. Marine winds similar to the last
few days as well, more details are below in the marine section.

.LONG TERM...
Key messages:
- The ridge breaks down at the start of the week as a weak
upper level low makes its way over the northern gulf.
- On Monday, overcast cloud cover returns with slightly cooler
temperatures.
- Precipitation chances return throughout the week, but rain
stays light with low QPF totals.

Details: A pattern change occurs at the start of the week as an
upper level low and trough push the ridge away from the panhandle.
This will increase cloud cover across the panhandle which will in
turn reduce maximum temperatures back down to the mid 60s. Along
with increased cloud cover, a short wave will bring precipitation
chances back to the panhandle very late Monday into Tuesday. The
timing for the start of precipitation has slightly changed moving
more toward Tuesday than Monday. For the start of the week, QPF
totals remain very low with only light precipitation expected.
Probabilities of greater than 0.5 inches of rain in 24 hours remain
below 50% for the entire panhandle and below 40% for southern areas.
So rain rates will be very light creating more of a nuisance rain.

Rain chances continue and slightly increase mid to late week as a
more structured system moves into the panhandle. Although chances
increase, no significant rain totals or impacts are expected at this
time. The most rain is expected Friday into Saturday, focused in the
northern part of the panhandle.

Winds along the coast will increase Sunday into Monday morning to 15
to 20 kts as the trough pushes the ridge toward the panhandle. This
will slightly increase the pressure gradient until the ridge weakens
and moves past the panhandle. Otherwise, slight increases in winds
will continue to occur during the afternoon hours in N. Lynn Canal
as a sea breeze tries to develop. Increasing cloud cover will help
to weaken any stronger sea breezes that develop, but a slight
thermal gradient will still be present. Winds in the gulf through
mid to late week remain light before increasing Thursday and Friday,
due to a low that moves into the gulf.

&&

.AVIATION...VFR conditions for interior TAF sites across southeast
Alaska Saturday night. Along the outer coast, a stubborn marine
layer will once again filter into coastal sites early Sunday
morning, as well as slither into Icy Strait, bringing CIGs below
1500 ft. Sites that saw fog Friday night can expect it to form
once more as conditions remain relatively similar. Surface winds
across the panhandle should remain 15 kts or less Sunday, with
the sea breeze at Skagway Sunday afternoon/evening being the
exception. No LLWS concerns for the TAF period.

&&

.MARINE...
Outer Waters: No big changes to wind magnitudes or directions for
the outer waters. Still expecting widespread fresh to strong NW
breezes (near 20 to 25 kt) along the outer coast this evening
into early tomorrow. Also, the marine layer currently over the
outer waters have descending clouds to the surface, resulting in
widespread fog with visibilities dipping down to 1 NM at times.
This fog will linger into tomorrow.

Inside Waters: Highly localized sea breezes are still expected
into Saturday evening. A thermal gradient around 10-15 degrees
between the outer waters and inside channels is still expected to
result in westerly winds in Icy Strait. Increased wind speeds in
Cross Sound and Icy Strait to around 15 to 25 knots for these
areas during the late afternoon and evening timeframe, when
heating is maximized. Less confidence for the Lynn Canal area,
specifically extending the higher wind speeds from Taiya Inlet
down to Eldred Rock, due to no real increased reported wind speeds
yesterday. For now, kept the current forecast going.

&&

.HYDROLOGY...Warmer-than-normal temps and high freezing levels over the
northern panhandle has increased snowmelt and runoff into streams.

The Chilkat River crossed into Minor Flood stage and with
continued warm air, the flooding will continue through tomorrow.
The Flood Advisory has been extended to 10PM Sunday but it may
need to be extended into Monday. Stay tuned.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Heat Advisory until 7 PM AKDT Sunday for AKZ319.
Heat Advisory from noon to 7 PM AKDT Sunday for AKZ331.
MARINE...Small Craft Advisory for PKZ022-641>644-661>664.

&&

$$

SHORT TERM...GJS
LONG TERM....EAB
AVIATION...STJ
MARINE...NC
HYDROLOGY...NM

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