Graphical Hydro Meteorological Discussion

728
FXAK68 PAFC 301230
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 AM AKDT Wed Apr 30 2025

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

Satellite imagery shows a low in the Gulf of Alaska continuing to
move northward with its front and southwesterly winds pushing
ahead of it. Through the next 48 hours, both will bring gusty
winds, precipitation and continued cloud cover to many across
Southcentral. Another storm is likely in Southcentral by week`s
end.

Multiple impacts are expected from this low today and tomorrow.
Winds will increase through this morning across Southcentral as
the storm`s front progresses. Northerly winds will remain strong
through the afternoon in the Copper River Basin and the Mat-Su
Valley. Wind gusts reaching 30 mph in the Gulkana and also the
Palmer/Wasilla area from mid-afternoon to the evening hours can be
expected. Blowing dust in the Palmer area is possible. Northerly
winds ahead of the front turn easterly during its passage then
southwesterly in its wake. A barrier jet forms late this
afternoon continuing into early tomorrow morning along the Prince
William Sound coast. Gale-force winds are expected during this
time.

Additionally, rain showers will spill over into Anchorage this
afternoon with the onset of southeasterly winds. QPF amounts
remain low for the afternoon and evening hours during the
scattered rain showers. Higher elevation snowfall accumulation
along the Gulf of Alaska and Prince William Sound coast continues
through tomorrow too with snow levels rising from 1800 feet to
around 2500 feet this afternoon and dropping to and remaining
around 2000 feet most of tomorrow. Rainfall in the Copper River
Basin will come in waves. The first, and stronger one, moves
through this afternoon and evening and after a brief lull,
another wave moves through tomorrow afternoon and evening.

-DJ

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Friday evening)...

A vertically stacked low pressure system continues its slow
northward progression from Bristol Bay this morning inland near
Togiak by afternoon. As it lifts north and continues to weaken,
the southeasterly winds through Kamishak Gap will also diminish by
this afternoon. Upper level temperatures near -30C will encourage
redevelopment of rain showers this afternoon as surface
temperatures approach 50 degrees in parts of the the Kuskokwim
Valley and Delta. Some showers may be intense but brief, but will
remain scattered in nature. Increased instability along the
Bristol Bay coast will also allow for another round of showers to
develop by noon. Isolated thunderstorms are also possible this
afternoon and evening, especially around Bristol Bay where
instability parameters are greatest. However, there may be just
enough cloud cover lingering into the afternoon hours to suppress
daytime heating and mitigate any significant convective
development.

That system continues to weaken overhead into Thursday, but rain
showers will become more isolated over time. On Friday morning, an
approaching disturbance from the Gulf of Alaska will return rain
to the Alaska/Aleutian range specifically. Overall expect
temperatures slightly above normal with scattered rain showers for
the next couple of days.

-TM/MTL

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Friday evening)...

Much of the Bering Sea and Aleutians is on the back side of the
weakening low pressure system. Cold air streaming southward will
promote scattered rain/snow showers and gusty northwesterly winds
through Thursday, decreasing in coverage and intensity through the
remainder of the week. The next system to impact the area will be
another frontal boundary approaching the western/central
Aleutians late Thursday into Friday. Model guidance is keeping
this system south of the Chain, enough to keep places like
Adak/Atka with snow as the precipitation type for a brief period
of precipitation on Friday.

-TM/MTL

&&


.LONG TERM FORECAST (Days 4 through 7/Saturday through Tuesday)...

Unsettled conditions will continue across southern Alaska as low
pressure sits over the Bering Sea and an active southern track
keep systems moving into the Gulf of Alaska. Broad cyclonic flow
with excess moisture will allow for showery precipitation and
enhanced northerly gap winds for much of Aleutians and Southwest
AK. The embedded closed low that brought moderate to high rates of
precipitation to coastal Southcentral midweek will slowly
dissipate as it works inland over Prince William Sound on
Saturday. Continued damp onshore flow will produce showery rain
and mountain snow through the weekend.

An upper level trough traversing just south of the Aleutians will
phase with the Bering low, pivoting it into the Gulf of Alaska on
Sunday. This system looks to bring yet another round of breezy
conditions and precipitation to the Gulf coast, from Kodiak to the
Panhandle.

&&

.AVIATION...

PANC...VFR conditions expected to persist through the TAF period.
Light rain is expected early this afternoon. Ceilings could drop
to 5000 ft or a little lower at times this afternoon into the
evening along with a lower scattered deck as well. Confidence is
low on development on an MVFR ceiling. Ceilings lift above 5000 ft
this evening and persists through Thursday morning.

Southeast winds early this morning flip back to north and persists
through early afternoon. Any low-level wind shear also ends this
morning as winds turn north throughout the column. Southeast
winds out of Turnagain Arm return this afternoon with gusts up to
25 kts at times through the evening hours before flipping back to
north Thursday morning.

&&


$$

266
FXAK69 PAFG 292326
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
326 PM AKDT Tue Apr 29 2025

.SYNOPSIS...A weakening 990 mb low is tracking northeast along
the Alaska Peninsula this afternoon with rain showers and patchy fog
across the YK Delta. Ahead of the low, south winds through the
Alaska Range passes increase this afternoon with gusts to around 50
mph continuing through Wednesday morning. Gusty east winds and
blowing snow continues at and near Point Lay through the end of the
week. We`re also monitoring the potential for a round of heavy
precipitation Friday night and Saturday across the south-central and
eastern interior.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...

-Strong winds develop for Isabel and Windy Passes this afternoon
through Alaska Range passes are expected through tonight. A Wind
Advisory is in effect for Isabel Pass north to Delta Junction
through Wednesday morning with gusts up to 50 mph expected.

-Southerly Chinook flow across the Alaska Range results in generally
warm and dry weather across the Tanana Valley through Thursday night
or Friday. High temps in the 40s and 50s are expected.

-Locally heavy rain/snow mix appears increasingly likely for Friday
night through Saturday night across the south-central and eastern
interior. Heavy high elevation snow is possible across the eastern
interior.

West Coast and Western Interior...

-Rain and snow showers are expected tonight across the YK Delta and
Yukon Valley with partly to mostly cloudy skies and patchy fog
possible elsewhere. Another round of rain/snow showers is possible
for a similar area Friday night into Saturday.

-Northerly winds through the Bering Strait and over St. Lawrence
Island at around 25 mph continue through Wednesday.

-High temperatures will be mainly in the 30s near the coast and in
the 40s and 50s in the Interior.

North Slope and Brooks Range..

-A mix of clear skies and low stratus will persist across the Arctic
Coast and North Slope with generally good visibility, except near
Point Lay. East winds gusting to around 40 mph and blowing snow will
likely continue through Saturday.

-Lows will be mainly in the single digits with highs in the teens
along the coast and in the 20s in the Brooks Range.

-The Brooks Range will be mainly dry under partly cloudy to mostly
clear skies through Tuesday.

&&

.FORECAST ANALYSIS AND DISCUSSION...Downslope flow across the Alaska
Range continues through Thursday night as a vertically stacked
low gradually weakens over Bristol Bay. Warm and dry Chinook flow
today gradually backs to moist easterly flow by Thursday night. An
energetic and negatively tilted trough pivots across the Gulf of
Alaska on Thursday night before shifting north across the Alaska
Range on Friday. EFI guidance paints most of the eastern interior
with high chances (60-80%) of unseasonably heavy QPF between 00z
Saturday and 00z Sunday. Ensemble means advertise around 1/2" of
QPF in Fairbanks resulting from cyclonic flow around a surface low
located along the AlCan border. This dynamic system may result in
heavy high-elevation snowfall across the White Mountains and
along the Dalton Highway Summits. While snowfall in the valleys
can`t be ruled out if heavy precipitation rates align with
nocturnal cooling, impacts appear limited to elevations above
1,000 to 1,250 ft. High pressure persists across the Arctic with
persistently strong east winds and blowing snow potential to the
Point Lay area all week. The pressure gradient tightens as low
pressure develops across the interior on Saturday, perhaps
bringing strong east winds and blowing snow potential to more of
the Arctic Coastline.

&&

.FIRE WEATHER...Downslope flow continues through midday Wednesday
with sustained south winds 20 to 30 mph and gusts to 50 mph through
Alaska Range passes. The latest model guidance indicates winds
subside Wednesday afternoon when deeper mixing and minimum RH values
occur. So far on Tuesday, RH values have struggled to fall due to
fairly thick cloud cover and easterly low level flow preventing
downslope flow from moving north. While downslope flow is likely to
move north on Wednesday, recent precipitation and the lack of drying
today implies RH may struggle to fall to critical levels. With that
said, RHs values may dip into the 20s from Delta Junction across the
Tanana Flats. Red Flag conditions on Wednesday are therefore
unlikely and increasing moisture as flow backs southeast on Thursday
limits fire weather concerns late this week.

&&

.EXTENDED FORECAST DAYS 4-7...Models are in good agreement that an
energetic 500 mb low pressure system tracks over Prince William
Sound Thursday night. A large chunk of that upper low moves across
the Alaska Range on Friday and closes off and deepens along the
AlCan Border Friday night through Saturday. The current set up looks
favorable for moderate to locally heavy rain/snow showers to occur
throughout the Central and Eastern Interior. Showers are expected to
be rain during the day, transitioning over to snow at night. Light
rain/snow showers appear likely for the western interior, but they
may not reach the West Coast before reaching the West Coast. Clouds
and precipitation across the interior late Fri thru early Sun keeps
daytime temperatures below normal and nighttime temperatures near
normal. A trend toward below normal temperatures is possible early
next week across the eastern interior. The Arctic Coast and North
Slope stays cooler than normal under chilly high pressure with areas
of low stratus.

Coastal Hazard Potential Days 3 and 4...None

&&

.EXTENDED FORECAST DAYS 4-7...
Coastal Hazard Potential Days 3 and 4...None


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Wind Advisory for AKZ837-849.
PK...Small Craft Advisory for PKZ806-812-851.
Heavy Freezing Spray Warning for PKZ806-812-851.
Brisk Wind Advisory for PKZ807.
Brisk Wind Advisory for PKZ810.
Gale Warning for PKZ811.
Brisk Wind Advisory for PKZ814.
Brisk Wind Advisory for PKZ815.
Small Craft Advisory for PKZ816.
Heavy Freezing Spray Warning for PKZ816.
Brisk Wind Advisory for PKZ817-854-856-858.
Gale Warning for PKZ857.
&&

$$
EK

704
FXAK67 PAJK 301328
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
528 AM AKDT Wed Apr 30 2025

.SHORT TERM...
Early Wednesday morning a broad open longwave trough is
enveloping the majority of the Aleutian Arc, stretching south into
the north pacific. Embedded just downstream of the main trough
axis is an energetic shortwave trough ejecting northeast, with the
surface baroclinic instability inducing cyclogenesis. The
surrounding wind field, as seen from 06z ASCAT passes, highlight
strong breezes, with the main dynamics heading toward the Kenai
Peninsula. Previous 18z HREF surface wind shows agreement with the
current situation, bringing southeasterly gale force winds to
most of our coast into Wednesday afternoon, with strong gales
likely near Cape Suckling. More on winds in the marine section.
Diving into precip type and intensity, ECMWF EFIs highlight strong
agreement on above m-climate normal QPF, with Scripps CW3E tools
showing IVT and wind near or above the 95th percentile. Look for
heavy rainfall to envelop the northern coast this afternoon,
spreading into the Panhandle into Thursday. Certainly, an active
pattern for the start of May.

.LONG TERM.../Thursday through Tuesday/
Unsettled weather conditions expected due to multiple low
pressure systems and moist onshore flow from the Gulf. SE AK
weather for the long range will be cool and wet. Aloft, a broad
upper low is in place across the Bering for the middle to end of
the week then pivoting to the Gulf by next weekend and next
Monday. Brief periods of ridging tracking however no foreseeable
long or substantial breaks in the next week, and from CPC outlook
likely the next two weeks. Periods of rain last into the weekend
as the parent low reaches the Central AK Gulf but rates and
overall coverage diminish. Yet another gale force low with heavy
rain tacks in for the end of the weekend and the start of next
week. More moderate to heavy rain depicted by EFI tables. Likely
more days of 24 hour rain accumulations of an inch to 2 inches
with near records amounts for this time of year. Ensembles and
operational models are still in fair agreement and any differences
not enough to alter previous forecast.

&&

.AVIATION...
Mixed bag of flight conditions across the area this morning, with
VFR to MVFR across the southern and interior panhandle down to
IFR flight conditions near Yakutat as a potent wave pushes into
the north Gulf coast. For the rest of this afternoon, worst flight
conditions will remain near Yakutat as the potent upper wave
pushes into the Gulf coast, with CIGS AoB 1000ft and intermittent
visibilities down to 2 to 3SM within heaviest showers. Elsewhere
among SEAK TAF sites, expect similar conditions to yesterday, VFR
to upper-end MVFR with CIGS AoB 5000ft through Wednesday morning,
gradually improving to predominate VFR through the early afternoon
primarily across the southern panhandle. Elevated winds continue
for Skagway and Haines TAF sites, with sustained winds up to 20kts
and isolated gusts up to 30kts possible, decreasing through 00z.
Elsewhere across the panhandle, winds should remain around 15kts
or less through this afternoon, however, can`t rule out a rogue
gust up to 25kts.

Not expecting this reprieve to last however as a secondary system
approaches the southern Gulf coast by Wednesday night into
Thursday morning, returning widespread precipitation, elevated
winds, and LLWS across the panhandle. By Thursday morning, expect
flight conditions to deteriorate to predominate MVFR or worse with
CIGS AoB 4000ft and intermittent reduced visibilities.

Main aviation concern through the forecast period will be LLWS
for coastal and southern panhandle TAF sites. Anticipate
southeasterly LLWS around 1000 to 2000ft to continue for Yakutat
through Wednesday afternoon, as highlighted by the Alaska
Aviation Weather Unit, maximizing near 50kts by 18z through 00z.
By Thursday night the aforementioned secondary system pushes into
the southern panhandle, SE- ly LLWS will increase for southern
panhandle TAF sites such as Sitka, Klawock, and Ketchikan, up to
30kts by 00z, increasing to near 50kts by 12z Thursday.

&&

.MARINE...
Outside:Southeasterly winds continue to escalate along our coast,
with gale force expected before the afternoon. Main forecast
update includes the classic barrier jet of Cape Suckling, where
high resolution guidance is showing strong agreement of sustained
easterly strong gales with gusts to storm force. Expect peak winds
Wednesday late-morning into the early afternoon; however, gale to
near-gale force winds continue into Wednesday night, spreading
into Dixon Entrance. Buoys on the outside as of 3am show a broad
spread of westerly wave energy, however, significant heights are
below 8ft. This story will change through Wednesday morning as the
aforementioned wind field drives fresh seas of 15 to 18ft out of
the south.

Inside:Overnight, the highest winds continued to be in Lynn Canal
where Eldred Rock was seeing fresh to strong breezes out of the
south. As a gale force low moves into the western gulf, the
isobars become more north-south orientated signaling a slight
decrease in winds for Lynn. Meanwhile Clarence Strait increases to
fresh breezes through the day. Easterly winds will also start to
be pulled out of Icy Strait, likely reaching moderate to fresh
breezes. Wednesday night winds really increase across most inner
channels with all areas seeing at least strong breezes, some areas
of gale force likely for Clarence.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from this evening through late tonight for AKZ323.
MARINE...Gale Warning for PKZ036-641-642-651-652-661>664-671-672.
Small Craft Advisory for PKZ021-022-031-033>035-053-643-644.

&&

$$

SHORT TERM...AP
LONG TERM....PRB
AVIATION...NM
MARINE...AP

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