Gale Warning 11, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
545 AM AKST Tue Jan 11 2022

.ANALYSIS AND UPPER LEVELS...

An elongated upper low remains nearly stationary over the central
Aleutians. Widespread showers extend across the much of the Chain,
with precipitation falling as mostly all rain, except across the
far western Aleutians where winds are more northerly. This will
continue for the near-future as the low remains stalled. While
radar shows precipitation over the Kuskokwim Delta, much of it is
likely not reaching the ground, though overcast skies persist in
the southerly flow aloft east of the aforementioned upper low.

Snow continues to develop from south to north across Southcentral.
Sleet/light freezing rain has been observed in Anchorage and over
Kenai Peninsula, including Seward. The latest 12z Anchorage
sounding shows a surface temperature near 23F and a very shallow
above- freezing layer centered near 925 mb. However, generally all
snow looks likely for most of Southcentral through today.
Temperatures in Cordova remain in the upper 30s, so they remain
the exception with rain continuing there. Much of the Copper River
Basin remains dry, though precipitation will likely occur near
higher elevations.

&&

.MODEL DISCUSSION...

Embedded shortwaves with the overall southerly 500 mb flow pattern
remain the biggest source of model disagreement. All show a
shortwave axis moving over Kodiak Island early Wednesday morning.
Solutions begin to diverge more significantly thereafter with the
latest GFS bringing the following wave in much slower than the
NAM/ECMWF. It likewise indicates precipitation starting later
across the western gulf ahead of an approaching broad surface low
on Thursday morning.

&&

.AVIATION...

PANC...

Light snow will persist across the terminal though this morning
leading to MVFR ceilings and possible brief periods of IFR
visibility. VFR ceilings/visibility will likely return by
afternoon, though may fall to MVFR at times. Light winds will
persist through Wednesday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Tuesday
and Wednesday)...

A weak upper level wave will move from south to north over the
area today bringing widespread precipitation to most areas. The
front that transmitted the area on Monday helped to usher in some
warmer air, especially at mountain top levels. This is causing the
snow to melt as it falls through the layer and fall as mixed
precipitation across a fair portion of Southcentral. While Seward
and the Anchorage Bowl observed freezing rain overnight, it was
rain for Whittier and the Portage Valley. Special Weather
Statements have been issued for potential hazardous travel
conditions through these areas. Meanwhile, colder air is holding
on further inland, so precipitation is falling as all snow across
the Mat-Su Valleys.

Colder air should filter back in with this system later this
morning for most areas ending the threat of mixed precipitation.
We still generally expect about 1-2 inches of snow accumulation
around the Anchorage area. For the Mat Valley, amounts could be
several inches higher with colder air and favorable SW flow.
Generally expect about 2-4 inches around Palmer and Wasilla with
upwards of 6" possible for Hatcher Pass by late this evening.

Southerly flow will keep the pattern active across the area.
Another wave of energy will follow nearly an identical track north
over the Kenai Peninsula on Wednesday. This will bring another
healthy dose of QPF to the western portions of Prince William
Sound. While this will mean more rain for locations at sea level,
the system will bring snow to elevations above roughly 500 ft.
While cross-barrier flow will keep locations from Kenai to
Anchorage dry on the leading edge of this feature, another brief
shot of snow could move through late Wed into early Thu. A much
stronger system starts to take shape in the Gulf by Thu. This will
bring a return to some breezy offshore winds early in the day
before the front crashes into Prince William Sound later on.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: Today
through Thu night)...

Unsettled conditions continue through Thursday night. An upper
level low and its associated surface low are located in the
Central Aleutians. Temperatures will steadily increase through
Wednesday as a warm front tracks northward. The influx of moisture
with this front, as well as shortwaves transiting around the
upper level low, will lead to areas of light snow. Along the AKPEN
and southern portions of Bristol Bay, temperatures may warm
enough to lead to rain/snow mix or rain. The primary challenge
with this forecast remains with the timing of upper level
shortwaves, which in turn affect precipitation timing. Regardless,
only minor precipitation accumulations are expected with this
feature.

On Thursday, a North Pacific low approaches the AKPEN. Some model
discrepancies remain with how quickly this low tracks towards
Alaska. This forecast package leans towards a faster-moving
system, so precipitation is forecast to begin along the AKPEN by
early Thursday morning. As with the previous system, warm air
advection will produce some areas of rain and mix. For now, most
of the precipitation is expected to remain along the Aleutian
Range and the Kuskokwim Mountains. Precipitation chances in areas
such as King Salmon and Iliamna will be reduced due to
downsloping.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3:
Today through Thu night)...

An upper level low and its associated surface low in the Central
Aleutians will dictate weather in the Bering and across the
Aleutian Chain through Thursday. In the Western Aleutians and
across much of the Bering Sea, northerly flow will continue to
bring colder temperatures and the potential for snow showers. In
the Central and Eastern Aleutians, rain will slowly taper off
into Tuesday. As cold air aloft wraps back around the low Tuesday
through Wednesday, there is a potential for snow or rain/snow
showers in the Eastern Aleutians. However, some uncertainty
remains with precipitation type. While temperatures aloft are cold
enough to support snow, there may be a thick enough layer of
warmer near-surface temperatures (aided by above-freezing SSTs)
to keep precipitation as all rain. By Thursday, cold conditions
take hold over the entire Bering and Aleutians as an approaching
North Pacific low ushers in a northerly flow regime.

&&

.MARINE (Days 3 through 5/Thursday through Saturday)...

Gulf of Alaska: A low near the AKPen with warm air advection will
bring a front northward through the Gulf Thursday. Gale force
winds are possible as the front creates a barrier jet along the
coast and through Kamishak Bay through Thursday evening. Gales
could extend into Prince William Sound. Winds should diminish
Friday morning through Saturday. Another low will develop and lift
into the Eastern Gulf, elongating a trough that will move into
the Northern Gulf coast Saturday morning. Seas around 20 feet on
Thursday evening subsiding slightly Friday and Saturday to around
15 to 20 feet.

Bering Sea: A widespread area of gales and large
seas of more than 20 ft will sweep across the Bering/Aleutian
Chain starting Fri night through Sat night as a result of a strong
North Pacific low. The associated front from the low will usher
strong gap winds for the Aleutians and potentially strong gales
across Pribilof Islands by Sat night. Warm temperatures associated
with this system should minimize freezing spray risks over the
central Aleutians for the next few days.

&&

.LONG TERM FORECAST (Days 4 through 7/Friday through Monday)...

A low near the AKPen area will move inland with an associated
trough northward towards the end of the week. Scattered snow
showers are possible for southwestern Alaska and periods of heavy
rain and snow spreading along the Gulf Coast from west to east
throughout the weekend. Out west along the Central and Western
Aleutians, a series of developing lows will usher in periods of
heavy precipitation throughout the weekend. Precipitation could
start as snow but expect any snow to transition to rain. Brief,
relatively quieter weather is possible Monday for South Central
and east.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 173-176 178 185 411-413.
         Heavy Freezing Spray Warning: 185 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KC
MARINE/LONG TERM...CB/VR