Gale Warning 22, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
504 PM AKST Mon Jan 24 2022

.ANALYSIS AND UPPER LEVELS...

A large low pressure system has made its way into southern Alaska.
The low has pushed into the Kuskokwim Delta with snow and blowing
snow west of Bethel and a rain/snow mix from Bethel east. The
associated front is moving across Bristol Bay and the Kenai
Peninsula extending into the northern Gulf. This is producing rain
to most lower elevation areas, however pockets of snow have been
observed at Valdez and along the Seward highway near Turnagain
Pass. Winds are also gusty in a few areas, with the Knik winds
blowing into the Matanuska Valley with 40 to 50 mph gusts common,
these are expected subside later this evening. Also gusty winds
to 60 mph are possible through this evening along the Turnagain
Arm and Anchorage Hillside. Otherwise across the Bering, Aleutians,
and AKPen quieter weather with northwest flow and a few snow showers.

&&

.MODEL DISCUSSION...

Models are in good agreement with the synoptic features, but
some differences arise on how long precipitation will persist
on Tuesday which will affect how much snow will occur across
Anchorage and the Matanuska Valley on Tuesday. The main challenge
will be timing the change of rain to snow across Southcentral.
The GFS has been the outlier keeping QPF through Tuesday afternoon
and evening while all the other models end the precipitation by
Tuesday around 18z for Anchorage and the Mat Valley. Models are
also coming into better agreement for Wednesday and Thursday with
a low pressure system moving north across the Gulf interacting
with a trough moving across Southcentral Alaska which keeps cold
air over the area. This will likely bring snow to most parts of
Southcentral. Last but not least, a deep low pressure system near
950 mb will bring strong winds to the Western Aleutians and
Western Bering Tuesday night into Wednesday.

&&

.AVIATION...

PANC...A weak surface low in Cook Inlet this evening, will
maintain east-west pressure gradients. As a result, gusty
southeast winds coming out of Turnagain Arm will continue to
bend into the terminal through the evening hours before gradually
weakening overnight. Similarly, southeast low level flow this
evening will continue to produce downslope drying with VFR
conditions. As this flow weakens overnight light precipitation
will move into Anchorage. This will initially be in the form of
rain and ceilings will not lower much right away. Expect a
transition to snow between 12Z and 15Z as heavier precipitation
and cooler air moves in. This will drop ceiling/vis to at least
MVFR, with potential for a very brief period of IFR conditions
depending on time of transition from rain to snow. Precipitation
will then end at the terminal by 18Z with rapidly improving
ceiling/vis.

&&

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

A weakening surface low continues to track northeastward along
the west Gulf Coast this evening. Its front is located onshore
over the north Gulf Coast with an associated deep moisture fetch
from the central Pacific. This warm, moist southerly flow in
combination with the front continues to force gusty winds and
considerable amounts of rain across the Gulf and along the coast.
As the surface low moves northward into Tuesday, steady
precipitation will continue overnight, but gusty winds will
continue to diminish and surface temperatures will start to
decrease. Thus, rain is expected to transition to snow late
tonight and early Tuesday morning. Slick roadways are expected
due to the recent warm temperatures combining with any new snow
formation. Snow is expected to end before noon on Tuesday for
western areas of Southcentral (Kenai Peninsula, Anchorage, Mat-
Su), but linger through the afternoon hours for eastern Prince
William Sound and the Copper River Basin. Decreasing clouds behind
this system will lead to colder temperatures over the next couple
days.

On Wednesday, a North Pacific surface low will lift northward
into the Gulf, spreading snow to Kodiak Island and up to
Southcentral. Meanwhile, weak short-wave troughs crossing western
Alaska Wednesday look like they will phase into a single stronger
short-wave trough Wednesday night. There is quite a bit of
uncertainty in the track of this short-wave. However, it has
potential to interact with the moisture moving up from the Gulf
low and lead to more widespread and heavier snow across the
region. Stay tuned as we monitor these features and hone in on
snowfall accumulation.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 to 3: Tonight
through Thursday)...

A much quieter and colder pattern will set in across the Southwest
as the low that brought a mix of mainly wet snow and rain to the
area departs to the north. Lingering snow over eastern parts of
Bristol Bay and the Middle Kuskokwim Valley will continue to move
out to the northeast, with partially clearing skies and quickly
cooling temperatures down to near 0F by tomorrow morning. Later on
Tuesday, a fast-moving and compact low pressure will sweep across
the Kuskokwim Delta, sending a cluster of light snow showers
inland through the early afternoon. Little to no snow accumulation
is expected with this weak system, with the rest of the Southwest
remaining cold and dry through midweek. Offshore winds will
increase on Thursday as the pressure gradient tightens between a
North Pacific low approaching the southern Gulf and Arctic high
pressure centered near the Bering strait. These winds could
coincide with cold enough temperatures to produce bitterly cold
wind chills in the -20 to -30F range, especially across the
Kuskokwim Delta on Thursday morning.

&&

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

Generally benign conditions will persist across most of the
forecast area initially on Tuesday as surface high pressure
remains centered over the southern Bering, with widely scattered
snow showers rotating around the ridge and occasionally crossing
over the Aleutian Chain and across the Pribilofs. By Tuesday
afternoon, a powerful North Pacific low will deepen with the aid
of jet coupling overhead to as low as 950 mb a few hundred miles
south of the western Aleutians. The low will reach peak intensity
before approaching the western Bering, but it's frontal axis will
drive winds to storm force into areas west of Adak, with gusts
near Hurricane force possible near the peak of the easterly winds
early on Wednesday morning. A band of rain and snow will work
north with the front, with temperatures warming above freezing and
preventing there from being much possibility for blowing snow
with the strong winds. The parent low pressure will slowly weaken
as it moves into the western Bering on Thursday, but gusty gale to
storm force winds and periods of rain will continue over much of
the western Bering/Aleutians near the low through Thursday
afternoon.

&&

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

Gulf of Alaska: A front extending from a North Pacific low will
continue to advance toward the northern Gulf coast on Thursday.
North-northwesterly gale force winds will develop from Cook Inlet
through Shelikof Strait from Friday to Saturday afternoon. As the
low weakens and exits out of the Gulf Saturday evening, expect
winds less than 35 kts and seas less than 20 ft. Forecast
confidence is moderate.

Bering Sea/Aleutians: A strong North Pacific low will lift
northwestward near the Kamchatka Peninsula on Thursday. Widespread
gale force winds with a potential of storm force gusts and
elevated seas above 20 ft will extend from the western Aleutians
to the northern Bering through Thursday afternoon. Forecast
confidence is moderate to high as model guidance remains in good
agreement with most of the active weather staying west of the
Pribilof Islands and Central Aleutians. A second North Pacific
low will approach the southern Bering Sea on Friday morning.
There is a potential for another round of gales and elevated seas
extending across the same regions from Friday through Saturday.
However, there is still model uncertainty with the overall track,
position, and strength associated with this low. Therefore,
forecast confidence with Friday's system is low.

&&

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

Overall, the latest operational model runs are in good agreement
with the synoptic scale features in the short term, but begin to
diverge toward the end of the period. Synoptically, an omega
blocking pattern will setup over the western Alaska region by
Friday with the amplified ridge axis over the eastern Bering Sea.
Downstream of the ridge, a cold, Arctic trough over mainland
Alaska will move southward, while an upper level wave lifts north
toward the AK-Yukon Territory. A surface low in the Gulf will
keep unsettled conditions for Southcentral with moderate to heavy
precipitation across the coastal areas and inland valleys. As the
low exits out of the area, precipitation will taper off from north
to south by Sunday. Benign conditions with temperatures near to
or below normal will prevail for the southern mainland as the
aforementioned ridge shifts over the state. Out west, a series of
deep Pacific lows will move north across the Western Aleutians,
bringing periods of gusty winds, rain/snow mix, and elevated seas
at times for the northern Bering Sea. Although there is uncertainty
in placement, strength, and timing with these systems, a wet
pattern will be the main theme as we head into the weekend. Some
of the precipitation and wind may extend across the Pribilof
Islands, the Central/Eastern Aleutians, and AKPEN for early next
week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Heavy Freezing Spray Warning 160 185.
         Storm Warning 177 178.
         Gale Warning 130 131 155 175 176.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...AF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...MF

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
936 PM AKST Mon Jan 24 2022

AKZ101-111-251900-
Anchorage-Matanuska Valley-
Including the cities of Anchorage, Eagle River, Indian, Eklutna,
Palmer, Wasilla, Sutton, and Chickaloon
936 PM AKST Mon Jan 24 2022

...LIGHT RAIN MONDAY EVENING WILL CHANGE TO SNOW TUESDAY
MORNING...

Light rain falling across the Anchorage Bowl and Mat-Su Valleys
this evening will change to snow during the overnight hours.
Temperatures will fall overnight and will reach the freezing mark
by early Tuesday morning. Precipitation combined with falling
temperatures will create slick conditions, particularly during
the Tuesday morning commute. While little to no ice accumulation
is expected, snow accumulations should generally range between 1-2
inches. Be aware that snow could fall on surfaces that have
already received rain, making conditions potentially more
hazardous.

Motorists are urged to use caution and slow down when traveling.
For the latest road conditions call 5 1 1 or visit 511.alaska.gov.