Gale Warning 357, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
509 AM AKDT Thu Apr 28 2022

.ANALYSIS AND UPPER LEVELS...
Reflectivity on radar just after midnight have areas of
convective cumulus and showers moving north of Bethel and King
Salmon. Showers are also developing just southwest of Talkeetna
and moving north. Low levels of the atmosphere continue to remain
dry and these showers are likely producing virga to a trace of
precipitation at the surface. Over PWS from Cordova to Valdez and
the northern Gulf to Whittier and Seward and south to just off the
coast of Kodiak Island, lower clouds and stratus are visible on
nighttime microphysics satellite.

The upper level ridge over Southwest mainland Alaska is
flattening as an upper level low over northern Alaska rotates and
pushes the airmass southward. A few stronger low centers embedded
within a large trough extends from the western to the central
Aleutians and Bering Sea. Southerly, low level moisture is
allowing for low clouds and stratus across most of this area with
periods of rain, snow, and reduced visibility at St Paul,
Unalaska, and Adak as the front moves across the Aleutians.

&&

.MODEL DISCUSSION...
Model agreement generally aligns well with the upper low to the
north, the development of the low over the Aleutians and Bering,
and the progression of the associated front that is expected to
bring precipitation and strong southeasterly winds through the
Barren Islands and Kamishak Gap through the rest of this week. As
the front progresses through the weekend, some subtle differences
appear along the north and northeastern Gulf coast and the
subsequent weakening of this low going into the beginning of next
week.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. An isolated
chance of showers and virga showers in the vicinity will be
possible through about 18Z this morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Today through Saturday
Night)...

The mostly quiet stretch of weather along with above normal
afternoon temperatures continues through Saturday. A weak
disturbance has caused a few nuisance showers to develop over the
Mat-Su this morning, but will quickly dissipate as they track
into the northern Susitna Valley. A large dome of upper level high
pressure will be shifted off to the east and will largely
dissipate. A large upper level low will try to take its place, but
with the eventual track of the low expected to take aim at the
Gulf, limited moisture will make it inland.

The associated surface front currently over the Eastern Aleutians
will gradually push east towards Kodiak Island. Expect gusty
southeasterly flow with rain developing all over the island by
Friday night. The front will stall and pivot as it reorients
itself, but the gusty southeasterly winds and steady rain will
continue into Saturday night. There is significant uncertainty by
Saturday night as to the track of a low that will develop along
the front. This will be the main factor as to how long the rain
will last in Kodiak. For the rest of Southcentral, there is also
some uncertainty as to how far north the associated precipitation
will get, which will be determined by the storm track.

&&

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

High pressure lingers over parts of Southwest today ahead of an
approaching front. Skies should remain mostly clear through today
before cloud cover rolls back in tonight ahead of the front. Most
of Southwest will remain dry through Friday, with most of the
rainfall trailing along the AKPen and spilling into northwestern
Bristol Bay. Winds will most likely be the biggest factor,
increasing along the coast throughout today and tonight ahead of
the front. The front pushes over the Southwest coast by Friday
morning and gusty southeast winds push inland.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Longwave troughing continues across the Bering over the next
couple of days. Today and tonight, winds will hang around small
craft until the front reaches the eastern Bering later tonight.
South to southeasterly winds will ramp up overnight tonight,
starting with gap winds. By Friday morning, winds increase to gale
force along the Southwest coast as well as waters south of the
AKPen. Widespread rain showers are expected along the frontal
boundary as well. The heaviest precipitation will be along the
southern AKPen, with periods moderate-to-heavy rainfall across the
Central and Eastern Aleutians through tomorrow night.

&&

.MARINE (Days 3 through 5: Saturday through Monday)...

Gulf of Alaska: High pressure exits the Eastern Gulf for Sunday.
A low forms over the Southern Gulf early Sunday and remains nearly
stationary. Its front anchored by the low extends across the Gulf
through Monday. Forecast confidence is good. Increasing winds
with the front become widespread high end gales, wrapping the low
and diminishing Monday. Seas to 12 feet, subsiding.

Bering: A Central Bering low merges with the Gulf low on Sunday.
A strong North Pacific low and front tracks over the Aleutians
through Monday. Forecast confidence is fair, but decreases with
the track of the Western Low through Monday. Gusty Easterly winds
over the Northern Bering diminishes by Sunday. Seas to 12 feet,
subsiding. Gusty winds increase to high end gales wrapping the
Western low as it move to the Eastern Aleutians for Monday. Seas
to 16 feet on the Pacific side of the Western Aleutians subside
Saturday, then build to 22 feet along the Pacific side of the
Central Aleutians through Monday.

&&

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

Looking ahead in the extended forecast, the latest operational
model runs are in decent agreement with the evolution and
progression of the synoptic scale features, but begin to diverge
in the specific details towards the end of the period. For
Southcentral, a front extending ahead a Gulf low maintains
precipitation along the coast on Sunday, while inland valleys
remain relatively dry due to downslope flow. By Monday, another
front associated with a secondary low tracks along the north gulf
coast, keeping the wet pattern going through the middle of next
week. Out west, a North Pacific low approaches the Western
Aleutians late Saturday, with the attendant front bringing rain
and gusty winds across the Chain and Bering Sea through early Tue.
The strongest winds stays south of the forecast area as the main
center of the low exits out of the area. By the middle of next
week, benign conditions can be expected a weak ridge of high
pressure builds overhead.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 150, 155, 160, 165, 170, 172, 180, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...VR
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
MARINE/LONG TERM...MK/MF