Small Craft Advisory 976, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
533 AM AKST Wed Dec 7 2022

.ANALYSIS AND UPPER LEVELS...

The main synoptic feature is an upper trough over the Bering
Strait extending southeastward into the Gulf of Alaska. At the
surface, a low pressure system is currently situated south of
Prince William Sound (PWS). An impressive deformation band on the
north side of the low pushed into Southcentral overnight.
Elsewhere, light to moderate snow has fallen from the Kenai
Peninsula up into the Mat-Su, and PWS up into the Copper River
Basin.

Mostly clear skies and strong radiational cooling is allowing
overnight temperatures to drop down below freezing across the
lower elevation regions in Southwest Alaska. Meanwhile, westerly-
northwesterly flow aloft persists over the Bering Sea. A weak
shortwave coupled with colder air interacting with the relatively
warm waters is bringing convective snow showers over the Pribilof
Islands and along the eastern Aleutians. Further west, a
developing North Pacific low is moving toward the western and
central Aleutians.

&&

.MODEL DISCUSSION...

The latest operational model runs are in decent agreement with
the placement and intensity of synoptic scale features at both the
surface and in the upper levels. Forecast remains on track for
light snow to continue today over Southcentral, but is expected
to begin tapering off as the aforementioned low moves southward
across the Gulf. Out west, the NAM seems to be the outlier
bringing the North Pacific low further north of the Aleutian
Chain, while the other solutions move the low across the Aleutians
and then south into the Pacific on Thursday.

&&

.AVIATION...

PANC...Snow will become lighter this morning with ceiling and
visibility conditions improving to MVFR. By late afternoon, snow
will come to end with VFR and light winds through the TAF package.

&&

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

The upper level short-wave which has been sitting over the
northwest Gulf and Cook Inlet since last evening will dig
southeastward into the central Gulf today. A closed upper level
low will develop and help pull the existing surface low over the
northern Gulf southward. Until then, snow will linger across much
of Southcentral. The heaviest snow will be on the northern to
western side of the Chugach and Kenai Mountains, where cold air
advection and upslope flow will support increasingly low density
snow right along the mountains. This includes east Anchorage,
Eagle River, and the Hillside. Snow will taper off for most areas
by this evening, though light snow will linger longer in the
Copper River Basin due to continued weak cyclonic flow aloft on
the north side of the exiting low along with upslope flow on the
north side of the Chugach Mountains.

Cold air advection along with tightening pressure gradients as
the low exits across the Gulf and high pressure builds in from
the north and west will lead to strong gusty gap winds through
area mountain ranges along with widespread strong winds across the
Gulf waters. As is typical, some of the strongest winds will be
through coastal bays, including Resurrection Bay, Passage Canal,
and the Valdez Narrows and Arm. With a strong low level jet coming
down across the western Susitna Valley into Cook Inlet, this is a
favorable set-up for gusty northwesterly winds in north to west
Anchorage this afternoon and evening. This of course will lead to
some localized areas of blowing snow.

As we continue through the remainder of the work week, the upper
low will exit to Southeast Alaska while an upper ridge amplifies
over the eastern Bering/western Alaska. This will serve to
maintain strong northerly flow and bring another round of cold
air advection. As a result, expect gap winds to persist and
temperatures to steadily fall, becoming quite frigid by week's
end sub-zero temperatures inland and single digits to teens likely
elsewhere.

&&

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

Benign weather conditions persist through the end of the week
across Southwest. High pressure builds in the eastern Bering,
producing northwesterly flow across Southwest. Colder air
continues filtering in across the region, with gradually
decreasing temperatures through Friday.

&&

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

Winds will continue to come down across the Bering. Colder air
will continue to filter through the Alaska Peninsula, which will
keep increased winds through the gaps and passes south of the
AKPen through the end of the week. There are a couple of low
pressure system pushing into the Bering Sea in the upcoming days.
The first of which crosses over the Central Aleutians late
tonight. There is minimal impacts associated with this low, some
small craft winds and light precipitation along the Aleutian
Islands. The second system is expected sometime late Friday. There
is still quite a bit of inconsistency with this low, however,
there will likely be areas of gale force winds and precipitation
along the associated front.

&&

.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...Storm 130 131 351 352
		 Gale 120 121 125 127 129 132 136-139 150
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MF
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...BL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1005 AM AKST WED DEC 7 2022

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

0522 AM     SNOW             6 SSE ANCHORAGE         61.14N 149.82W
12/07/2022  M14.5 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            14.5 INCHES STORM TOTAL. MEASURED. SNOW FELL
            FROM 1PM DEC 6 THROUGH 5:15AM DEC 7.

&&

KO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1006 AM AKST WED DEC 7 2022

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

0539 AM     SNOW             4 NNW WASILLA           61.63N 149.49W
12/07/2022  M10.0 INCH       MATANUSKA-SUSITNA  AK   NWS EMPLOYEE

            6 INCHES SINCE 10PM ON DEC 6.

&&

KO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1009 AM AKST WED DEC 7 2022

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

0607 AM     SNOW             2MI SE EAGLE RIVER      61.30N 149.53W
12/07/2022  M14.2 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            STORM TOTAL 14.2 INCHES. 30F. CALM.

&&

KO

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
1023 AM AKST WED DEC 7 2022

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

0626 AM     SNOW             11 SSE ANCHORAGE        61.07N 149.77W
12/07/2022  M12.1 INCH       ANCHORAGE          AK   PUBLIC

            12.1 INCHES TOTAL EVENT FROM AFTERNOON OF
            DEC 6. STILL SNOWING.

0631 AM     SNOW             10 SE ANCHORAGE         61.10N 149.72W
12/07/2022  M13.0 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            13 INCHES IN 24 HOURS. 6 INCHES FELL SINCE
            2200 ON DEC 6. 1300 FEET ELEVATION.

0700 AM     SNOW             5 SE ANCHORAGE          61.16N 149.81W
12/07/2022  M14.5 INCH       ANCHORAGE          AK   PUBLIC

            NO WIND.

0700 AM     SNOW             4 E ANCHORAGE           61.22N 149.76W
12/07/2022  M16.1 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            16.1 STORM TOTAL SINCE SNOW STARTED MONDAY.
            13.2 INCHES IN LAST 24 HOURS. STILL SNOWING.
            AVERAGE RATIO FOR THE EVENT 14 TO 1.

0700 AM     SNOW             7 SSE ANCHORAGE         61.11N 149.85W
12/07/2022  M16.5 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            BOARD WAS CLEARED 3 TIMES. LIQUID MEASURED
            AT 1.04 INCHES. SNOW DEPTH IS 19 INCHES.

0737 AM     SNOW             1 SSE SUTTON            61.71N 148.87W
12/07/2022  M2.5 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

            ANOTHER 2.5 INCHES OVERNIGHT. VERY LIGHT
            SNOW NOW.

0757 AM     SNOW             11 SSE ANCHORAGE        61.07N 149.77W
12/07/2022  M12.5 INCH       ANCHORAGE          AK   PUBLIC

            STILL SNOWING.

0800 AM     SNOW             9 SE ANCHORAGE          61.12N 149.72W
12/07/2022  M13.5 INCH       ANCHORAGE          AK   TRAINED SPOTTER

            NO BLOWING OR DRIFTING, STILL COMING DOWN.

0855 AM     SNOW             8 SE ANCHORAGE          61.13N 149.72W
12/07/2022  M15.0 INCH       ANCHORAGE          AK   PUBLIC

0914 AM     SNOW             2 SSE KODIAK STATION    57.74N 152.50W
12/07/2022  U0.5 INCH        KODIAK ISLAND      AK   PUBLIC

            BLOWING SNOW IN KODIAK WITH VISIBILITY DOWN
            TO 1 1/2 SM.

0936 AM     SNOW             4 S ANCHORAGE           61.17N 149.88W
12/07/2022  M12.0 INCH       ANCHORAGE          AK   PUBLIC

            SNOW FALLING, NO WIND, NO DRIFTING, TOP
            LAYERS LIGHT AND FLUFFY, BASE IS WET STICKS
            TO SHOVEL.

0943 AM     SNOW             11 SSE ANCHORAGE        61.07N 149.77W
12/07/2022  M14.5 INCH       ANCHORAGE          AK   PUBLIC

            14.5 INCHES TOTAL SINCE AFTERNOON OF DEC 6.
            STILL SNOWING STEADILY.

0957 AM     SNOW             10 SE EAGLE RIVER       61.26N 149.31W
12/07/2022  M14.8 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            MODERATE TO OCCASIONALLY HEAVY SNOW OVER THE
            PAST HOUR.

1000 AM     SNOW             10 SE ANCHORAGE         61.10N 149.72W
12/07/2022  M17.0 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            ADDITIONAL 4 INCHES SINCE 630AM. STORM TOTAL
            17 INCHES.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1026 AM AKST WED DEC 7 2022

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

1025 AM     SNOW             9 SE ANCHORAGE          61.12N 149.72W
12/07/2022  M16.0 INCH       ANCHORAGE          AK   PUBLIC

            TOTAL SNOW SINCE 3PM DEC 6. STILL SNOWING.
            ACCUMULATING AT ONE INCH PER HOUR.

&&

KO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1055 AM AKST WED DEC 7 2022

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

0536 AM     SNOW             4 ENE BIG LAKE          61.54N 149.83W
12/07/2022  M15.0 INCH       MATANUSKA-SUSITNA  AK   NWS EMPLOYEE

            STILL SNOWING.

&&

KO