Small Craft Advisory 74, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
519 AM AKST Tue Jan 25 2022

.ANALYSIS AND UPPER LEVELS...

Cold air in the upper levels push into Southcentral early this
morning and will mix into the lower levels, decreasing
temperatures back to below freezing and transitioning rain to back
to snow. A large North Pacific low moves into the Gulf of Alaska
towards the end of the week, however, its front pushes into the
Gulf by Wednesday morning, reaching the Coast by Wednesday
evening. There are still some model discrepancies regarding how
far westward over Southcentral the precipitation makes it before
the front fizzles out. Further west, another large, vertically
stacked low tracks towards the Western Aleutians on Wednesday
before shifting northwards towards the Kamchatka Peninsula. Its
front will impact the Western and Central Aleutians as well as
the western portions of the Bering Sea Wednesday and Thursday.

&&

.MODEL DISCUSSION...

Models are in good overall synoptic agreement through the long
term and have come into better agreement for the development of a
weak surface low just south of PWS. The NAM, who was showing
development significantly further north yesterday, has since
adjusted further south and is lining up more with the GFS. There
is still a fair amount of discrepancies with the North Pacific low
pushing towards the Gulf of Alaska mid week. Specifically, with
how far north and how quickly its front approaches the North Gulf
Coast, as well as how far inland the precipitation travels.
Solutions are handling a large low west of Shemya rather well
across all parameters. Model spread begins to grow by Thursday
morning regarding center location, with some light difference on
low strength.

&&

.AVIATION...
PANC...Periods MVFR to IFR conditions will persist through much of the
morning hours before improving to VFR by late morning/early
afternoon. Winds will continue to gradually diminish throughout
the day.

&&

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

The system bringing the warm weather is still in place over
Southcentral Alaska early this morning, but it will be on its way
out soon. Cold air from the west and southwest is already moving
up Cook Inlet and this will spread eastward throughout the course
of the day. Precipitation type in Anchorage and the Mat-Su is still
a little tricky this morning. Rain has turned to snow in Kenai,
but, as expected, the persistent southerly winds 10 to 20 mph in
Anchorage have kept temperatures warm and in the upper 30s to
lower 40s all night. These temperatures will drop later this
morning as the colder air arrives, but the big question will be
whether the precipitation will end before the colder air can turn
it to snow or is there is a burst of snow to accompany this
morning's rush hour. Still think there can be a short period of
snow after the southerly winds end this morning.

There will be partial clearing skies over most of Southcentral
tonight before the next system begins to move over Kodiak Island
and then begins to spread into inland Southcentral Alaska
Wednesday and Wednesday night. This is an interesting system and
much different that the last one. The cold upper level low that is
over Southwest Alaska will move eastward as a front reaches from
a low well south of the Gulf into Southcentral. This inverted
trough setup is one that can bring a persistent snow to
Southcentral Alaska as it pushes moist air aloft over colder
surface air without strong cross-barrier flow to downslope out
the precipitation. It is looking more likely for an area-wide snow
beginning Wednesday night or Thursday depending on location. A
day or two ago it looked like the moisture would remain mainly
over the Copper River Basin but subsequent model runs are all
pushing it westward to the Alaska range so that would hit the Cook
Inlet through Susitna corridor as well as the Copper River Basin.

Kodiak will be on the cusp of the rain-snow line with this one.
Temperatures look to get into the upper 30s in Kodiak City so that
does indicate it should turn to rain. However, the winds will
remain northerly and that could keep precipitation mostly snow
even with temperatures above freezing. This will be a focus of
the next few forecasts.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...

Temperatures will trend colder this forecast period for Southwest
Alaska. On the upper level pattern (500 mb) there is a weak
trough with a shortwave near Cape Newenham. As this shortwave
moves inland today scattered/light snow showers will be possible
but significant accumulation is not expected. A number of
locations will have clear skies this week. As a result, expect
the temperatures to nose dive once the sun sets. Additionally,
there is an Arctic high setting up over the Bering Strait. By
Wednesday morning Bethel and Nightmute will be back to negative
single digits. Dillingham and King Salmon will reach single
digits.

&&

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

The longwave pattern features a broad trough over the western
Bering. The models continue to trending towards an active pattern
with a fierce North Pacific low impacting the Aleutians. This
morning, at the surface there is a 957 mb low will be south of
Attu Island. The models track this low towards the Western
Aleutians this evening. By Wednesday morning, this low will have
advanced even closer to Attu and deepened to 953 mb. Impacts-
wise expect storm force to hurricane force winds and rough seas
(+30 ft) along with a wide precipitation shield. There is an
Arctic high that sets up over the Bering Strait and influences the
eastern Bering. This low will follow the path of least resistance
and the worst conditions will materialize in the NW Pacific,
Western Aleutians and Western Bering.

&&

.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...Storm Warning 177 178 411
	 	 Gale Warning 130 132 138 150 155 175 176 412 413
		 Heavy Freezing Spray Warning 160 185 412 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KM
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
MARINE/LONG TERM...MF

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1048 AM AKST TUE JAN 25 2022

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

1048 AM     SNOW             SOUTHWEST WASILLA       61.50N 149.69W
01/25/2022  M2.0 INCH        MATANUSKA-SUSITNA  AK   NWS EMPLOYEE

            SPOTTER REPORTED 2 INCHES OF NEW SNOW IN
            WASILLA AND WAS STILL SNOWING.

&&

MV

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1050 AM AKST TUE JAN 25 2022

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

1050 AM     SNOW             LATE OTIS & HUFFMAN ROA 61.11N 149.83W
01/25/2022  M4.0 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            SPOTTER REPORTED 4 INCHES OF NEW SNOW.

&&

MV

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1053 AM AKST TUE JAN 25 2022

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

1053 AM     SNOW             UPPER HUFFMAN AROUND 12 61.11N 149.73W
01/25/2022  M4.0 INCH        ANCHORAGE          AK   NWS EMPLOYEE

            SPOTTER REPORTED 4 INCHES OF NEW SNOW.

&&

MV

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1137 AM AKST Tue Jan 25 2022

AKZ101-111-252200-
Anchorage-Matanuska Valley-
Including the cities of Anchorage, Eagle River, Indian, Eklutna,
Palmer, Wasilla, Sutton, and Chickaloon
1137 AM AKST Tue Jan 25 2022

...BAND OF LOCALLY MODERATE TO HEAVY SNOW MOVING ACROSS THE
ANCHORAGE BOWL AND MATANUSKA VALLEY OVER THE NEXT ONE TO TWO
HOURS...

A band of locally moderate to heavy snow has developed across the
Matanuska Valley and Knik Arm with snowfall rates of of up to an
inch per hour. Visibility may be reduced to as low as one half to
one quarter mile at times in the heaviest snow. Please slow down
and use caution when travelling.

This band will slowly move west to east across the region through
the next one to two hours before weakening and eventually
tapering off.

For the latest forecast, visit www.weather.gov/afc.

For the latest road conditions call 5 1 1 or visit 511.alaska.gov.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
237 PM AKST TUE JAN 25 2022

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

1048 AM     SNOW             SOUTHWEST WASILLA       61.50N 149.69W
01/25/2022  M3.5 INCH        MATANUSKA-SUSITNA  AK   NWS EMPLOYEE

            CORRECTS PREVIOUS SNOW REPORT FROM SOUTHWEST
            WASILLA. SPOTTER REPORTED 3.5 INCHES OF NEW
            SNOW IN WASILLA AND WAS STILL SNOWING.

&&

MV

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