Small Craft Advisory 56, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
432 PM AKST Wed Jan 17 2024

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

So far winds have been less impressive than originally forecast,
likely due to a combination of factors. First off, the strength of
the low-level inversion was impressive, with a 12C inversion just
750 ft from the surface and extending up to approximately 1500 ft.
Even with the strong upper level forcing, much of the wind has
remained above this inversion, which varies with height throughout
Southcentral. Another factor is the positioning of the upper
level shortwave, which has broadened and shifted to the east. This
has resulted in less concentrated downward forcing for the winds,
particularly for the Valdez area. Thirdly, forecasted pressure
gradients were considerably higher than what came to be through
the day today.

For the rest of the night there will still be an increase in winds
through the Mat Valley and Valdez area. This is mainly due to the
reorientation of the upper level wind field, which will help mix
down some wind as it becomes northeast to southwest. For the Mat
Valley, winds will continue to increase through the evening,
peaking around 55 mph, with gusts to 65 mph possible. Some blowing
and drifting of snow is possible. Winds will also clip the north
and west side of the Anchorage Bowl near Knik Arm, but again
should be about 10 to 15 mph lower than originally forecast.
Valdez will remain variable, with gusts up to 60-70 mph possible.
Otherwise, gap winds will lower across the board by Thursday
afternoon.

With the weaker winds and clear skies, temperatures will drop
steadily over the coming days with little to no precipitation in
the forecast for much of the area except maybe Kodiak Island by
the weekend. Fog and low stratus shouldn't be much of an issue
anymore due to increasingly dry air moving in from the north.

&&

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

More arctic air will influence the region. The longwave pattern
features a broad area of high pressure over southwest Alaska that
extends into the Bering and a 983 mb low south of Cold Bay.
Meanwhile over the interior the high will be at 1048 mb. A tight
pressure gradient has set up along the Aleutians. This pattern
will result in widespread single digits over much of the interior
southwest and below freezing temps along the coast while much of
the chain will remain above freezing. The gusty winds will
continue into tonight and through Wednesday. The models suggest
that gusty easterly flow will continue for the chain and Bering on
Thursday and Friday. Freezing spray is also possible by the
weekend extreme vessel icing may be possible from Bristol Bay to
St Matthew Island.

&&

.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...

The Western Bering upper level ridge continues its track into the
North Pacific through the period. A portion of the ridge
amplifies briefly as it moves over Western Alaska through
Wednesday. An upper level low tracks across the Arctic to the
Northwest Alaska Coast and adds support to a developing longwave
splitting Interior Alaska down to the Gulf before curving
Southwestward into the North Pacific. Models are in good
agreement, but diverge somewhat towards the end of the period. The
biggest weather influence through midweek will be the advection
of Bora-like colder temperatures and locally strong gusty winds
spreading across the interior to the Southwest and Southcentral
areas. A low in the Gulf for Monday will help pump moisture over
the coastal Southcentral zones from the Eastern Kenai to the
Canadian Border, but not advect very far inland through Tuesday.

Kutz

&&

.AVIATION...

PANC...VFR conditions will persist through the TAF period. Light
northerly winds will continue to increase through the remainder of
the day with gusts likely in the 20 to 30 kt range in the
afternoon and early evening. These gusty northerly winds look to
peak overnight tonight into early Thursday morning. Although not
likely, there is a low chance (20%) of a gust to 35 kts during
this time. The pressure gradient will relax into through the mid-
morning hours Thursday and winds should be begin to diminish as
well.

-TM

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
1156 PM AKST Wed Jan 17 2024

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

0930 PM     Non-Tstm Wnd Gst Thompson Pass           61.13N 145.74W
01/17/2024  M83 MPH          Chugach            AK   Mesonet

            Measurement taken from RHRA2 (RWIS) at the
            peak of the wind event.

&&