Gale Warning 684, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
351 AM AKST Fri Nov 25 2022

.ANALYSIS AND UPPER LEVELS...

Remnants of a weak surface low just south of Kenai will continue
providing disturbed conditions across Southcentral today, waning
and ceasing tonight. Conditions across Southcentral are expected
to stabilize as a ridge of high pressure begins to develop over
Central Alaska. Out west, zonal flow has established, and as the
high pressure builds, a mostly inactive pattern is expected for
Southwest through most of the weekend. One disturbance that will
bring some activity will be another North Pacific low entering the
Bering this late this morning. This system will bring rain to the
western Aleutians first as pushes eastward. How a low interacts
with building high pressure over mainland Alaska is a repetitious
problem in most models. That being said it is currently expected
that this low will deflect off of the ridge to the Northwest
Bering with a tailing longwave trough that may provide some
inclement weather along the Southwest coast beginning Sunday
morning/afternoon. Gusty offshore winds are possible in places
like Bethel as this boundary approaches. A low forming at the
triple point of this boundary is possible by Monday morning which
could push across the AKPEN into Kodiak Island by midday Monday,
however confidence is low on this.

&&

.MODEL DISCUSSION...

Models have come into much better agreement in the short-term
regarding the longevity of snow for the Anchorage area, with snowfall
easing by this afternoon. Forecast confidence begins high,
degrading by the late weekend. Some minor discrepancies regarding
showery activity as the shortwave moves out are still apparent
with the GFS advertising a slightly more lingering snow showers
for Anchorage than the other models. Models again are in good
agreement regarding the exit of this system, bringing an end of
snowfall to Southcentral by Saturday afternoon. The next source of
some model uncertainty is how the incoming North Pacific low
interacts with the building ridge over mainland Alaska by Sunday
afternoon. The GFS lingers the low in the Central Bering slightly
longer than the other solutions which eject it out to the
northwest Bering. This discrepancy also impacts the confidence on
the potential low forming at the triple point. If this low is
given enough development, which the Canadian and Euro solutions
see more so than the GFS, Kodiak Island could see some
precipitation Monday morning. Confidence by this time is low.

&&

.AVIATION...

VFR ceilings may lower to MVFR this today as snow showers move
through the region. Brief IFR visibilities are possible during
heavier periods of snow. VFR conditions will return by Friday
afternoon. Light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 2:
Today through Saturday night)...

A negatively tilted trough with surface low over the northern Gulf
will continue to bring light snow to the area. Expect lingering
snow through around mid-day for the Mat-Su Valleys as southwest
flow and upslope flow continue with another inch or so of snow
possible before it tapers off this afternoon. Anchorage may see a
few snow flurries or brief periods of light snow but accumulations
will be minimal. Otherwise, as the shortwave moves east this
afternoon cold air advection and upslope flow will develop which
should keep light snow going over the Anchorage hillside and Eagle
River area with another 1 to 2 inches of snowfall possible before ending
later this evening. The bulk of the heaviest precipitation will
be across the Prince William Sound area with rain and snow near
the coast near sea level. Light snow should spread across the
Copper River Basin this afternoon before tapering off tonight with
an inch or two of snowfall possible. As the surface low winds up
and moves east northerly gap winds will develop beginning this
afternoon and cranking up through Saturday night. This will usher
in colder and drier air with the snow moving out of the Copper
River Basin and Prince William Sound by Saturday morning. With
lingering snow along north and west facing mountains through
Saturday night due to upslope conditions.

&&

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

Overall, relatively benign weather conditions are expected across
Southwest Alaska through the weekend. There is some lingering
precipitation in some areas, primarily along the foothills of the
mountain ranges that will diminish through the morning hours.
Snowfall along the higher elevations will likely hold on longer
throughout the day. High pressure ridging pushes towards Southwest
on Saturday. Unsettled weather returns with the approach of a
front on Sunday afternoon. Precipitation will be a non-factor for
most areas excluding the immediate coast. Instead, increased
gusty winds will take over the Kuskokwim Delta and portions of
Bristol Bay as well as over the marine areas along the Southwest
Coast.

Additionally, Dillingham north to Koliganek have been locked down
in freezing fog overnight. Fog should lift by mid-morning.

&&

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

High pressure ridging exists over much of the Bering Sea through
tonight. A the front off a North Pacific low pushes into the
western Bering Saturday morning, the associated low follows on
Sunday morning. Along the front, expect areas of storm force
winds, mainly west-northwest of the Pribilof Islands Saturday
night into Sunday morning, as well as widespread precipitation.
There will also be widespread high end gale force winds as well.
This will be mostly impactful along the Pribilof Islands who could
see periods of blowing snow during highest winds Sunday morning.
The temperatures for the Pribilofs will be at or above freezing,
so snow will be wet and dense and mixed with rain at times. Heavy
wet snow is not as transportable as a light, drier snow, and a
wintry mix is even less so. Additionally, areas along the
Aleutian Chain and Southern Alaska Peninsula will see periods of
moderate-to-heavy precipitation (mostly rain in the lower
elevations) as the front progresses.

&&

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

The key feature in the long term is a building ridge over the
mainland, creating a highly amplified pattern for next week. By
Monday afternoon, an upper level trough over the Alaska-Yukon
border will be departing eastward. As an upper level ridge to the
west builds in, gusty outflow winds, particularly along the
northern Gulf coast, will be the main concern for much of Monday
into Tuesday. By Tuesday morning, an upper level shortwave
dropping southward will likely enhance the northerly winds for a
brief period. As the ridge builds over the mainland Wednesday,
generally quiet conditions are expected for Southcentral.
Meanwhile attention shifts to Southwest and the Alaska Peninsula
as models are all hinting at the arrival of a shortwave trough
Wednesday into Thursday. While confidence is low due to lack of
model agreement, this feature does have the potential to introduce
onshore flow and increase chances of precipitation for the end of
the week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warnings 119 120 125 130 131 173-178
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CL
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...KO