Small Craft Advisory 63, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 AM AKST Sat Jan 20 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Monday)...

We start the day with high pressure over Southcentral and a front
extending over the central Gulf of Alaska and Kodiak Island. The
significant inversion remains over Southcentral with peak
temperatures (many near or above freezing) between 2000 and 4000
ft. In places where it is windy, such as Wasilla, the warmer air
aloft is mixed downward keeping their temperatures in the lower
30s all night, whereas in nearby Palmer, winds are calm and with
temperatures in the lower teens at the same time. These winds are
expected to move over Palmer as the day goes on and today will
likely be the warmest day of the next few for most of Southcentral
due to an arctic trough moving into the area which will bring in
colder air at all levels and significantly weaken the inversion.
The front over Kodiak is stalling as it moves into the ridge over
the mainland part of the state. There is much warmer air with this
front so most of the precipitation near sea level on Kodiak is
expected to be rain today. One of the bigger questions for this
forecast package is when the precipitation type near Kodiak City
will change from predominantly rain to snow. This evening looks to
be the most likely time for this to occur.

As the trough moves over Southcentral, the gap winds are expected
to increase across the region and especially along the north Gulf
coast. These winds are not expected to be as strong as a few days
ago, but it will still get noticeably windy again in the usual
areas.

&&

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

Key Messages:

* A very cold, arctic airmass moves over Southwest Alaska through
  at least Monday. The combination of strong winds and cold
  temperatures will produce wind chills between -25 and -35F in
  the Kuskokwim Delta, with isolated locations in the Lower
  Kuskokwim Valley reaching near -40F by through Monday morning.

* Widespread freezing spray expected through the weekend for the
  Eastern Bering, Pribilof Islands, and coastal SW Alaska.

* Heavy to extreme Freezing spray expected from Bristol Bay north
  to St. Matthew Island. Icing rates of 4 cm an hour or greater
  are possible.

* Persistent 20 to 40 kt winds across SW AK, Bering Sea, and
  Aleutians through the weekend.

Discussion:

A synoptic trifecta of a retrograding high pressure system over
the W Bering, a stout mid/upper lvl longwave trough digging into
southcentral AK and a north Pacific Low will bring a shot arctic
air and frigid temperatures across much of SW AK through the
weekend. With these systems at play, a tight pressure gradient
will continue to support 20 to 40 knot east to northeasterly
sustained winds with gusts up to 50 knots through the weekend for
coastal SW AK, AKPen, and along the Aleutians with Gale warnings
persisting for the Bering, Pribilofs, Central and Western Aleutians
through early next week. This synoptic pattern will result in
widespread arctic air as low as -20F to -40F over much of the
interior southwest and single digit temps along the coast. Will
need to monitor for potential issuance of a Wind Chill Advisory
for the Kuskokwim Delta.

In addition, with elevated winds and intruding arctic air
dropping temperatures into the single digits/subzero, expecting
development of heavy freezing spray from Bristol Bay north to St
Matthew Island starting this afternoon, with extreme freezing
spray expected along coastal areas of the Kuskokwim Delta and
Bristol Bay and along the ice edge developing by late tonight
through early next week. Icing rates of 4 cm an hour or greater
are possible.

&&

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

An elongated upper level trough over eastern interior Alaska will
continue to shear out south and east over the Gulf ahead of
another approaching trough from the Gulf of Anadyr. This trough
will settle over interior Alaska and extend into the Gulf of
Alaska for the latter half of the period. At the same time, a
ridge continues to build over the Bering through Friday. An
elongated low complex should prevail south of the Alaska Peninsula
and eastern Aleutians. However, there is greater uncertainty
regarding the tracks and strengths of these lows. This should
confine precipitation to the southern coasts, with temperatures
remaining well below normal across Southcentral Alaska. Gusty
winds will promote wind chills between 20 to 40 below zero across
southern Alaska. Gale force winds develop through Cook Inlet,
Shelikof Strait, and the Barren Islands and last through the end
of the week. Gale force winds will also bring heavy, potentially
extreme freezing spray to Bristol and Kuskokwim Bays, with lesser
intense freezing spray into the Bering through early Thursday.

KZ/ME

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through much of
the TAF period. Winds could pick up briefly above 10 kts late
tonight into Sunday morning as a frontal system lifts northward
though the Gulf. Slightly stronger northerly winds over Cook
Inlet could clip the terminal then. Winds are expected to become
light again later Sunday morning and through the afternoon hours.

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
245 PM AKST Sat Jan 20 2024

AKZ155-161-211500-
Kuskokwim Delta-Bristol Bay-
Including the cities of Bethel, Nunivak Island, King Salmon,
Dillingham, Naknek, and Pilot Point
245 PM AKST Sat Jan 20 2024

...COLD WIND CHILLS EXPECTED ACROSS THE KUSKOKWIM DELTA AND
BRISTOL BAY TONIGHT THROUGH MONDAY NIGHT...

A very cold, Arctic airmass moves over Southwest Alaska through
at least Monday along with gusty north-northeast winds ranging
from 20 to 30mph. The combination of strong winds and cold
temperatures will produce wind chills between -20F and -35F across
the Kuskokwim Delta and Bristol Bay beginning tonight and
persisting through Monday evening. Northern Bristol Bay and
eastern Kuskokwim Delta will see coldest wind chills and may reach
as low as -40F Sunday night. Winds are expected to diminish
through the overnight hours Monday night into Tuesday.