Gale Warning 805, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
424 PM AKST Tue Dec 6 2022

.ANALYSIS AND UPPER LEVELS...

An upper trough axis remains centered over western Alaska.
Southerly flow ahead of it is helping to drive snow over
Southcentral. This will increase in intensity through this
evening as an associated low develops south of Prince William
Sound. A weak ridge is seen over the Bering, bringing more benign
conditions with only some ocean-effect show showers across the
eastern Aleutians.

&&

.MODEL DISCUSSION...

The main challenge today remains where the deformation snow band
forms on the backside of a developing low south of Prince William
Sound. Both high-res and synoptic models indicate an average QPF
around one inch over the Anchorage bowl, with newest runs not
deviating from this. Another low in the southern Gulf will
interact with the Prince William Sound low. This will impact where
the deformation band forms and will shift the position of the
locally higher snow totals.

&&

.AVIATION...

PANC...MVFR ceilings/visibilities are expected this afternoon,
with IFR conditions expected by this evening as heavier snow
builds into Anchorage. Snow will become lighter by Wednesday
morning and likely end completely by afternoon. Winds will remain
light.

&&

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

An incoming low pressure system currently located south of the
Kenai Peninsula aims to move along the coastline. A deformation
band on the north side of the system has pushed into Southcentral
and snow has begun in the Anchorage area. This area of deformation
will diminish and move out of the area ast the low shifts
eastward tonight into Wednesday. As such, forecast confidence has
improved regarding an imminent snowfall event for much of
Southcentral tonight and Wednesday morning. Along the coast, a
quick transition from mixed precipitation this afternoon to snow
will occur. The snowfall is expected to include light and periods
of moderate snowfall from Kenai, to Anchorage, to the southern
Mat- Su Valley this evening, persisting through tonight, and
diminishing Wednesday morning. Snowfall for Whittier, Valdez, and
Cordova are expected to persist on a similar timeline however with
lower totals expected. Snow from this system that reaches up into
the Copper River Basin will begin this evening, persisting until
Wednesday night, however totals are similarly lower than that for
Kenai, Anchorage, and southern Mat- Su Valley. Kodiak and the
southern tip of the Kenai Peninsula will likely not see
precipitation, and have mostly clear skies until Friday.

Additionally, this system will drive cold northerly flow as the
low tracks eastward. This colder air will bring gusty conditions
through Wednesday night, particularly to communities near the
Prince William Sound and the Southeastern Kenai Peninsula. This
flow pattern and gusty conditions are expected to persist through
Wednesday night into Thursday. This pattern will bring a sharp drop
to minimum temperatures by Thursday night. A deep chill will set
in Thursday night, with single digit temperatures along coastal
locations and negatives further inland.

&&

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

Conditions are clearing out across Southwest and a cooling trend
over the next couple days is expected. There are a few snow
showers that may occur, especially near higher terrain, as
conditionally unstable air moves east off the Bering Sea.

&&

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

Gales could linger near Saint Matthew and the Alaska Peninsula
tonight, but generally decreasing with time as a flattened ridge
moves across the Bering Sea and Aleutians over the next couple
days. An elongated trough with a developing North Pacific low is
moving toward the Western and Central Aleutians. There is still
some uncertainty with the strength and track of this low, but
winds look to begin ramping up Wednesday afternoon. As the low
moves across the Aleutians, the low weakens quickly as it starts
to move east. Along the same track, a slightly more vigorous low
quickly moves into the Western Aleutians by Friday morning and
could play a role in weakening of the previous low and the
placement of gale force wind potential and consequential
precipitation in the Bering Sea.

&&

.LONG TERM FORECAST (Days 4 through 7: Saturday through
Tuesday)...

The start of the forecast period will include high pressure
sliding across Alaska, as well as a very cold and dry air mass in
place over Southcentral. Operational models, specifically the GFS,
depicts 850 mb temperatures below -20 degrees over the Copper
River Basin, with surface temperatures potentially dipping down to
minus 40 degrees near Glennallen on Saturday. Over the Bering and
the Aleutians, ensembles are in relatively good agreement with
bringing a Bering trough eastward and into Southcentral Alaska
through the weekend. The first implication of the trough's
eastward movement will be to kick the colder airmass into Canada
while also promoting slightly warmer temperatures, albeit still
below freezing, across all of southern Alaska. The second
implication of the trough's eastward movement will be to advect in
a significant plume of moisture up from the North Pacific. While
several days away, with plenty of time for models to come into
better agreement, the stage may be set for a significant winter
storm system tracking into Southcentral when combined with the
above average moisture forecast to arrive over the weekend.
Confidence in timing of precipitation overspreading Southwest
Alaska is well below average, but increasing snow would be
possible as early as Sunday for Southwest Alaska based on latest
operational models, before snow expands into Southcentral early
next week on Monday.

Southwest and Southcentral look to remain in an active pattern
thereafter with the next potential low overspreading the Aleutians
with more wind and precipitation as early as Tuesday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 101 111 121.
MARINE...Gale 120 121 127 132-138 150 185.
		 Storm 130 131.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...CL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...VR
LONG TERM...BL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
955 PM AKST TUE DEC 6 2022

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

0946 PM     SNOW             11 SSE ANCHORAGE        61.07N 149.77W
12/06/2022  M6.5 INCH        ANCHORAGE          AK   TRAINED SPOTTER

            SNOWFALL TOTAL SINCE EARLIER IN THE
            AFTERNOON. SNOW STILL FALLING STEADILY AT
            TIME OF REPORT.

&&

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
957 PM AKST TUE DEC 6 2022

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

0946 PM     SNOW             RABBIT CREEK            61.07N 149.77W
12/06/2022  M6.5 INCH        ANCHORAGE          AK   TRAINED SPOTTER

            CORRECTS PREVIOUS SNOW REPORT. SNOWFALL
            TOTAL SINCE EARLIER IN THE AFTERNOON. SNOW
            STILL FALLING STEADILY AT TIME OF REPORT.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1008 PM AKST TUE DEC 6 2022

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

0900 PM     SNOW             SAND LAKE               61.15N 149.93W
12/06/2022  M9.5 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            SNOWFALL SINCE 7 AM THIS MORNING.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1014 PM AKST TUE DEC 6 2022

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

1000 PM     SNOW             EAGLE RIVER             61.32N 149.54W
12/06/2022  M6.5 INCH        ANCHORAGE          AK   NWS EMPLOYEE

&&