Gale Warning 221, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
525 PM AKST Thu Mar 6 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Thursday afternoon through Sunday afternoon)...

Through Sunday afternoon, generally expect unsettled weather
along the coast, with much quieter weather further inland.
Weatherwise, isolated to scattered showers linger this evening.
Then, by late tonight into early tomorrow morning, a low in the
Gulf pushes its front into Southcentral Alaska. The low will
linger in the Gulf through Saturday, then exit eastward as a front
and developing triple point low slide in from the Bering Sea.
Forecast confidence is moderate to high, with the lowest
confidence for marine-area forecasts with Friday's low. No
impactful hazards are anticipated at this time.

Diving into the details... clear skies today have led to
temperatures climbing into the 40s this afternoon. Middleton
Island radar shows isolated to scattered showers continuing to
move in along the north Gulf coast, though the latest returns show
a shift from southwesterly to southeasterly steering flow as the
atmosphere responds to a low moving into the Gulf. This low has
been the main source of forecast uncertainty; model guidance
continues to show poor consistency and poor agreement regarding
its track, leading to lower forecast confidence regarding wind
direction/speed and precipitation amounts/timing. Have gone with
a more northerly low track for this forecast package, though the
forecast on land isn't particularly sensitive to the low track
since the low itself remains offshore. Marine forecasts will be
much more sensitive to shifts in the low track, so mariners
should stay tuned to the forecast for tonight and tomorrow.

In addition to the low track, another aspect of uncertainty will
be with temperatures. Temperatures today were a bit higher than
forecast, thanks to the increasing daylight as we approach spring.
Temperatures through Saturday will likely be influenced most by
diurnal effects rather than air mass changes; this means that
confidence in surface temperatures forecast may be a bit lower as
these diurnal effects can be difficult for models to accurately
represent. Where this comes into play will be for precipitation
type forecasts along the coast, especially for Whittier.
Currently, our forecast calls for about 2 inches of snow in the
Whittier area Friday night into Saturday morning as temperatures
linger in the mid-30s. If temperatures are lower, there could be
greater snow accumulation. Overall, this likely won't have a big
impact, but it might be something to note for snow-lovers keeping
a close eye on the forecast.

-Chen

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Thursday to Sunday)...

As of this afternoon, there are a couple of features to note in
the Southwest. First, what is left of the stalled low affecting
Nunivak Island and the YK Delta is centered west of Nunivak and is
sending scattered snow showers to the Bethel area, with flurries
also lingering along the coast. There is still some degree of
blowing snow happening over Nunivak Island, but that should wind
down as northerly winds somewhat relax as the low begins to drift
southward and weaken considerably this evening. We still have
quite the pressure gradient over the Pribilofs, which is
continuing blowing snow across the islands. Farther west, a ridge
of high pressure has situated itself across the Western Aleutians.

Going forward into midday Friday, guidance shows the
aforementioned low continuing its trek southward, bringing with it
a broad and colder airmass across the Bering and into the central
Aleutians, AK Pen, and coastal Southwest as the ridge out west is
pushed quickly eastward across the Central Aleutians. By this
time, blowing snow should come to an end for the Pribilof Islands
as the pressure gradient weakens. A gale-force low with widespread
storm force wind gusts and gales quickly chases out the ridge
into the Eastern Aleutians and AK Pen by Friday night, as the
low's front steamrolls across the Central and Western Aleutians.
This setup becomes tricky as temperatures are cold enough to
initially support moderate to heavy snowfall and blowing snow,
which could warrant advisory products for the Central and Western
Aleutians. However, south of the triple point will be a sector of
relatively warm air of 40-45F, which will transition snow to rain
for these areas. Timing of the transition will be ironed out as
more guidance comes in, but as of now operational models show the
changeover hitting Adak late Friday afternoon, then quickly moving
eastward over Dutch Harbor by Saturday morning, and continuing
its march eastbound. As the whole system shifts eastward late
Saturday, blowing snow or blizzard conditions yet again look
likely for the Pribilofs. The hope is some of the strong
southeasterly flow will usher in some warmer air to limit pre-
frontal blowing snow potential, but blizzard conditions and a
period of heavy snowfall of 2-4" still look possible with winds in
the 50kt ballpark as precipitation moves in and the event
unfolds. We have above average confidence in impacts to the
Pribilof islands, which has prompted us to issue a Winter Storm
Watch from Friday night lasting until Saturday afternoon. Strong
southeast gales at the same time will stretch southward across the
Central and Eastern Aleutians.

By Sunday morning, the front, precipitation, and warm sector
reaches the AK Pen and Southwest coastline where we will similarly
see strong winds, moderate snowfall, and the snow changing to
rain from west to east. Some marginally colder air at the surface
and much colder air aloft attempts to wrap in the wake of this
frontal system, which could change lingering light precipitation
across the Aleutian chain back over to snow. Models do show
another round of gale force winds behind the front with strong
cold air advection across the southern Bering. Conditions for the
Pribilofs look to improve by this time frame as well. Apart from
that, the upper level and surface flow looks fairly zonal for the
rest of the short term.

-AM

&&
.LONG TERM FORECAST (Days 4 through 7 - Monday through Thursday)...

An extensive upper level trough stretching from the Russian Far
East across the Bering continues its Eastward push over Interior
Alaska into Northern Canada through the forecast period. A low
center separates from this trough at the Alaska Peninsula and
moves across the Gulf of Alaska before exiting to the Southeast
for Wednesday. A weak ridge moving over the Aleutians flattens out
by Thursday. An ECMWF / GFS and Canadian blended cluster
continues to handle features consistently well through the period.
Greatest uncertainty rests with the smaller details supported by
shortwaves rotating through the pattern.

A well developed surface low and front over the Central Bering
weakens and dissipates as it approaches Western Alaska by Tuesday.
Widespread snow and gale force winds over the Bering subsides by
late Tuesday. Meanwhile a low that formed on the front near Kodiak
Island pushes snow over the inland areas of Southcentral Alaska,
the Alaska Peninsula into Southwest Alaska, and areas of rain
along the coastal zones in Southcentral and over the Gulf,
diminishing late Tuesday. A strong North Pacific low and front
bears down on the Western and Central Aleutians late Tuesday
through Thursday. Locally heavy rains and gale force winds move
over the Aleutians, diminishing Thursday.

- Kutz

&&

.AVIATION...

PANC...VFR will prevail through the TAF period in wake of a frontal
system. Winds will become northerly this evening, becoming gusty
overnight before abating on Friday.

&&