Gale Warning 696, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
431 AM AKDT Fri Nov 4 2022

.ANALYSIS AND UPPER LEVELS...

A broad, cold, upper-level trough and its associated low continues
to be parked over northern Alaska. A surface low can be seen on
Water Vapor Imagery early this morning located along the Gulf of
Alaska coast near Cordova. Clouds are beginning to fill in due to
the troughs orientation helping to reinvigorate light snow showers
across the Southcentral region early this morning. Radar returns
are observed over the Matanuska Valley, Anchorage, Prince William
Sound, and the eastern Kenai Peninsula regions. Much drier air is
being brought into the domain as the flow has turned northerly,
making the majority of accumulations light in nature.

Further west, cold air advection upstream of the aforementioned
trough is bringing colder temperatures and strong northerly winds
across the eastern Bering and Southwest Alaska. The Kuskokwim
Mountains continue to be effective in blocking low-level clouds
resulting in widespread clearer skies for the Bristol Bay region
and Kuskokwim Valley as shown on Nighttime Microphysics Satellite
Imagery this morning.

&&

.MODEL DISCUSSION...

Models remain in good overall synoptic agreement through the
short-term. Model spread grows slightly with the subtle features
such as the timing of weak upper-level waves and how they may
impact the gusty gap winds that will occur the next few days along
the Gulf coast. This will be the main forecast challenge in the
coming days.

&&

.AVIATION...

PANC...Dry northerly winds will continue today with gusty
conditions possible this afternoon, keeping conditions VFR.

&&

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

A change in the weather pattern will bring colder temperatures,
clearing skies, dry conditions, and strong gap winds across the
area. An upper level low with some light snow across Anchorage,
the Matanuska Valley and Kenai Peninsula is moving southeast
across the Kenai Peninsula and will move through the Gulf this
will set the stage for strong northerly gap winds today. Another
shortwave will dive southeast fairly quickly across Southwest
Alaska today and cross Kodiak Island by the afternoon and evening
hours producing a few snow showers. This shortwave will reinforce
the strong northerly gap winds. Another shortwave will dive south
Saturday and will bring even colder temperatures across the
Copper River Basin. This shortwave is expected to produce a fairly
strong Matanuska Valley winds where a High Wind Watch is in effect
Saturday morning through Sunday morning. However, there is
uncertainty on the strength of these winds. The current thinking
is that sustained winds will be up to 45 mph with gusts up to 60
to 65 mph. So there is low forecast confidence right now that a
High Wind Warning will be needed for the Matanuska Valley.
Additionally, winds will increase across Thompson Pass and Valdez
where there is higher confidence in stronger winds occurring.
Currently a High Wind Watch is in effect for this area from
Saturday morning through Sunday morning. Current thinking is gusts
of 75 to 80 mph.

&&

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

Another quick shot of snow showers pushes into Southwest Alaska
beginning early this morning with the approach of a surface low
pushing out of Russia. Southwesterly onshore winds will continue
through this morning, transitioning to northerly as the low tracks
across the western Alaska Range. Cold Arctic air fills in behind
the system, dragging across Southwest towards the Alaska
Peninsula. With the cold air advection comes increased gusty
winds, most notable through the Kuskokwim Delta and along the
AKPen, as well as through the gaps and passes south of the AKPen.
The heaviest snow is expected to fall just ahead of the peak
winds, though, the combination of new, transportable snow
accumulations (though minor) and lingering falling snow will
create visibility issues at times. As such, Blowing Snow Advisories
have been issued for both the Kuskokwim Delta and Bristol Bay.
Note that the main area of concern for blowing snow through
Bristol Bay will be along the AKPen, from Port Heiden up to
Iliamna. However, other areas along the coast such as Dillingham
and Cape Newenham may also see periods of reduced visibilities due
to blowing snow, but overall conditions in these areas should
remain above Advisory criteria. New snow accumulations of up to 4
inches is possible in the Kuskokwim Delta and lower Kuskokwim
Valley today, with highest amounts expected along the Mountain
ranges. Up to 2 inches of new snow accumulation is possible across
Bristol Bay.

Conditions begin to improve by early Saturday morning as the low
moves out and an upper level ridge approaches Southwest Alaska,
drying it out. Winds should keep temperatures from lowering too
much tonight, even with less cloud cover. Clearer skies overnight
Saturday may promote some radiation cooling, with temperatures
dropping into the single digits, sub-zero in the lower Kuskokwim
Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

Cold air advection on the western flank of a surface low
traversing across Southwest Alaska will flow across the
Alaska Peninsula today. Gusty winds through the gaps and passes
south of the Alaska Peninsula are expected to increase this
evening and persist into Saturday morning. Additionally, areas of
snow and blowing snow may cause visibility issues along the
southern AKPen. There will be areas of freezing spray along the
immediate Southwest coast as well as south of the AKPen through
Saturday morning. Elsewhere, relatively benign weather is expected
underneath an upper level ridge. A frontal system moves into
the western Bering on Saturday morning and remains stationary
through Sunday morning. This is due to a North Pacific low pushing
northwards towards the Central Aleutians not allowing the front
to progress any further east. Gusty, storm force winds are expected
along the eastern edge of the North Pacific low and will reach
the Eastern Aleutians (near Nikolski) early Sunday morning. Along
with it will be areas of heavy precipitation for the Central and
Eastern Aleutians, Southern AKPen, and Pribilof Islands on Sunday.

&&

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

Strong model agreement in the synoptic pattern for Southwest
Alaska into Southcentral Monday shifts to mild uncertainty by
Wednesday. The cause of this divergence in solutions is a common
culprit, a deteriorating ridge over Southcentral. Models often
struggle on the breakdown of these ridges and tend to break them
down faster than what occurs. This will lead to some uncertainty
in the long term, particularly for how far east precipitation is
able to make it into Southcentral. The 12Z GFS solution breaks
down the ridge particularly quickly, swinging a low from the
Bristol Bay area into the Gulf by Tuesday afternoon. The 00Z
Canadian offers a more resilient ridge that fends off the low,
however swings a surface low bringing elevated precipitation
across Southcentral. Currently, it is difficult to tell how the
low will progress across the Alaska Peninsula due to the ridging.
Questions of how far north/east the low will push remain
debatable. Out west, after the low moves out to the east, much of
the strong precipitation features will have moved out and zonal
flow will set-up. Some models do suggest a North Pacific low
moving into the Central Aleutians by Thursday morning, however
this is not well agreed upon and time will tell. In summary, the
Bering Sea and Southwest Alaska is looking to be warmer and
wetter, while Southcentral will remain colder and drier.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 155, 161.
		 High Wind Watch: 111, 131.
		 Special Weather Statement: 125.
MARINE...Storm Warning: 120, 127, 130, 352.
		 Gale Warning: 119, 121, 125-126, 128-129, 131-132, 136,
					   138, 150, 155, 160, 165, 177-178, 180-181,
			           185, 351, 411-414.
		 Heavy Freezing Spray Warning: 120.
FIRE WEATHER...NONE.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1056 AM AKDT FRI NOV 4 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0815 AM     SNOW             1 SSE SUTTON            61.71N 148.87W
11/04/2022  M4.3 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

            STORM TOTAL SNOWFALL.

0614 AM     SNOW             EAGLE RIVER             61.30N 149.53W
11/04/2022  M4.6 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            PREVIOUS STORM TOTAL 4.4 INCHES TOTAL 9.0
            INCHES STORM TOTAL CURRENT: FLURRIES, 18F.

0928 AM     SNOW             15 E ANCHORAGE          61.23N 149.44W
11/04/2022  M6.8 INCH        ANCHORAGE          AK   PUBLIC

            TOTAL SNOW SINCE 10:30PM THURSDAY. VERY
            LIGHT SNOW STILL FALLING.

0949 AM     SNOW             11 SSE ANCHORAGE        61.07N 149.77W
11/04/2022  M0.8 INCH        ANCHORAGE          AK   PUBLIC

            NEW SNOW OVERNIGHT.

&&