Brisk Wind Advisory 3, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
509 PM AKST Mon Jan 3 2022

.ANALYSIS AND UPPER LEVELS...

The pattern remains highly amplified as a Rex Block is currently
developing across the Bering/Aleutians. The broad upper level
ridge associated with the developing Rex Block currently extends
northwestward across the central and eastern Bering/Aleutians into
Siberia. A deep upper level trough extends across the Gulf of
Alaska and the Alaskan mainland. A strong 1056 mb surface high
extends across the North Slope while low pressure is located
across the eastern North Pacific. The strong surface pressure
gradient is responsible for the strong offshore winds across
Southcentral and Southwest Alaska.

Radar shows minimal activity across Southcentral and Southwest
Alaska. Observations show strong northerly to northeasterly winds
across the areas. The strongest winds are located in the Matanuska
Valley where observations show frequent gusts of at least 50-60
mph. Extreme windchill values lower than -40F have also been
recorded at several observation sites in the Copper Basin as well
as a couple of sites in the lower Kuskokwim Valley.

&&

.MODEL DISCUSSION...

Forecast confidence remains above average due to good agreement
between guidance on the placement and intensity of synoptic scale
features. Higher resolution models such as the NAM Nest were
favored to resolve local effects (i.e. localized gap winds) due to
them having a good handle on the observations and a smaller grid
resolution to better resolve these smaller scale features.

&&

.AVIATION...
PANC...VFR conditions will continue for this TAF package.
Northeasterly winds at 010 degrees will continue at 15kts and
gusts to 25kts at times.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Tonight through Thursday)...

Dangerously cold wind chills will continue over parts of Susitna
Valley and Copper River Basin until noon Tuesday, and over
Thompson Pass through Tuesday afternoon as wind chills of 35 below
zero to 55 below zero extends over those advisory areas. Very
strong winds and higher gusts up to 75 mph are possible over
Matanuska Valley tonight through at least Wednesday afternoon. A
mix of cold air advection and strong pressure gradient over
Southcentral will keep winds elevated with much greater gusts
along the foothills the next couple days. Strong gap winds will
also continue especially along the coastal areas and more
noticeably around Copper River Delta, Prince William Sound, and
along the Shelikof Strait and Kamishak Bay through the Barren
Islands through at least Wednesday night. These winds combined
with cold temperatures will cause heavy freezing spray to extend
near several coastal areas through Tuesday night.

Isolated troughs transiting from east to west over the Gulf could
enhance increased clouds and rain/snow mix tonight through
Tuesday night. Part of this phenomenon will at least bring snow
over Kodiak between Tuesday and Tuesday night. Meanwhile, much of
Southcentral is expected to remain mostly clear to partly cloudy
through Thursday as the ridge of high pressure lingers over
eastern Southcentral through the middle of the week.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: Tonight
through Thursday night)...

A cold air mass over much of the state will begin to retreat
eastward through Thursday. High pressure centered over the Bering
is forecast to continue lifting northward while several waves of
low pressure dig southeastward into western Canada. The end result
will be a subtle but appreciated "warm-up" with calmer winds
expected over Southwest. Subsidence or sinking motion in the
atmosphere will keep any precipitation at bay the next few days
with a notably dry air mass to remain over interior Southwest
through Thursday. Elsewhere, northerly winds over the Alaska
Peninsula will gradually veer to an easterly direction. This will
end the threat for elevated gap winds through the bays and passes
later tonight. Low-level Gulf moisture and easterly flow over the
peninsula will promote periods of off and on light snow Tuesday
night through Wednesday night from Cape Sarichef to Chignik,
especially along the south and southeast mountain faces.
Accumulations, however, are expected to remain negligible outside
of the higher elevations.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3: Tonight
through Thursday night)...

Elevated northerly winds are ongoing across the Eastern Aleutians
this evening while a strong pressure gradient persists between
high pressure over the Bering and low pressure over the Gulf. High
pressure will slowly lift northward into the Chukchi Sea through
tomorrow, allowing the pressure gradient over the eastern Bering
to finally weaken. At the same time northerly winds will veer to a
easterly direction, putting an end to the threat of gap winds
across the Eastern Aleutians. To the west, enhanced southeasterly
winds are clipping the Western Aleutians along with isolated light
rain. Wind and rain are occurring in the vicinity of a near-
stationary front draped northwest to southeast over the Western
Aleutians. Through tonight this front will drift westward and away
from the Aleutian Chain as a small wave of low pressure ejects
from the Alaska Peninsula into the western Bering. The next
frontal system will arrive late Tuesday. A North Pacific low is
forecast to interact with an easterly shortwave trough skirting
just north of the Aleutians. Increasing showers, initially snow,
will then transition to rain, likely over the latter half of the
day on Wednesday, as strong warm air advection accompanies the
low's passage over Dutch Harbor. All in all, it looks to be an
active week with widespread, easterly gales to impact much of the
southern Bering through Thursday.

&&

.MARINE (Days 3 through 5/Thursday through Saturday)...

Bering/Aleutians...

Forecast confidence remains high for the 3-5 day period.
Widespread easterly gale force winds will veer southeasterly
Thursday morning across the central and eastern Bering/Aleutians.
This southeasterly veering of the winds will reduce the chance of
freezing spray in the 3-5 day period.

Gulf of Alaska...

Forecast confidence remains high for Thursday and Friday as
surface high pressure extends across the Gulf. Winds will remain
below gale force and no high seas expected. Confidence then
decreases to low Friday night and remains low on Saturday as
guidance shows significant differences in the placement and
intensity of the next frontal system that is expected to move
through the region during that time.

&&

.LONG TERM FORECAST (Days 4 through 7/Friday through Monday)...

The pattern is expected to remain cold across the Alaskan mainland
during the extended period as the dry and cold off shore wind flow
continues. Confidence is much lower with respect to the chances
for precipitation later this weekend into early next week as a
complex pattern is expected. The pattern is complex due to the
southerly-southeasterly onshore geostrophic flow around the
Aleutian low combined with the strong north-northeasterly offshore
ageostrophic (pressure gradient driven) flow as strong surface
high pressure will continue to extend across the North Slope and
Alaska Interior while the Aleutian low deepens. This could mean
the "competing flows" may result in precipitation being confined
only to windward locations south of the Chugach and Kenai
Mountains. 850 mb and 925 mb winds are expected to remain out of
the northeast on Sunday and Monday which will lower the confidence
of snow in the Anchorage Bowl as the next frontal system moves
into the area during that time.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning: 111.
         Wind Chill Advisory: 141, 131, 145, 161, 152.
MARINE...Gale Warning: 127, 128, 130, 138, 139, 411, 412, 413,
         414, 150, 155, 165, 170, 171, 172, 173, 174, 175,
         176, 177, 178, 179, 180, 181, 185.
         Heavy Freezing Spray: 119, 121, 126, 127, 128, 129,
         130, 139, 141, 414, 155, 160, 165, 179, 180, 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ED
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BL
MARINE/LONG TERM...ED