Small Craft Advisory 6, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...

Bora winds are continuing with unrelenting force across
parts of Southcentral this morning, with a core of particularly
strong winds gusting at times over 80 mph continuing to shoot out
across the Matanuska Valley out of Chickaloon Pass from the
northeast. Damage and widespread periods of power interruptions
have been reported across the Palmer vicinity, where winds have
now gusted almost continuously above 60 mph for more than 24
hours. The corridor of strongest winds is beginning to shift
slightly west into the Wasilla area as the wind direction shifts
from northeast to slightly more east-northeast, with gusts
increasing to around 75 mph at times in Wasilla proper during the
past several hours. A High Wind Warning remains in effect for the
area, now extended in time through much of the day today with the
expectation for the Mat Valley winds to persist for longer.
Strong winds are also bending down into mainly the far west side
of Anchorage as well, with gusts occasionally as high as 50 to 60
mph recorded on the north and west side of town earlier in the
evening on Sunday. Gusty north to northeast winds are also
continuing elsewhere across parts of Southwest, as well as through
the typical gaps along the North Gulf Coast including the Valdez
Arm, Thompson Pass and Copper River Delta. Another corridor of
strong northerly winds gusting up to Hurricane force continues to
blow south of the Alaska Peninsula, roughly halfway between the
Shumagin Islands and Kodiak Island. Extremely cold wind chills
between -25 and -45F also continue for the areas seeing gusty
winds, with actual temperatures mostly in the single digits above
to teens (or lower) below zero across most of the southern
mainland.

All of the winds mentioned above have been made possible by an
unusually steady-state and rather extreme contrast between two
synoptic scale features. A very strong, blocking ridge continues
to sit over the northern Bering aloft, with maximum sea level
pressure as high as 1055 mb over parts of the North Slope in
association with the very cold/dense Arctic air becoming
entrenched over much of the state. Meanwhile, a deep and nearly
inverted trough axis extends from the Gulf into Southcentral and
the Alaska Peninsula, with much lower surface pressure around 985
mb persisting in the southeastern Gulf near the low drifting slowly
away from the forecast area. The very strong pressure gradient
and strong northeast flow between the opposing high and low
centers is combining with advection of bitterly cold air spilling
through gaps and passes (especially those that connect with the
Copper River Basin) to produce the long duration wind event well
underway.

Out in the west, things are remaining fairly steady-state as well,
with a stalled front focusing southeast gale force winds along
the western Aleutians and across the southwestern Bering. Steady
rain continues to fall along the front, mainly for locations west
of Amchitka.

&&

.MODEL DISCUSSION...

Model agreement for synoptic scale features remains well in check
through the middle of the week. Smaller scale details with the
ongoing winds continue to be the main short range forecast
challenge, with some lingering uncertainty for how quickly the
winds will begin to subside through gaps across Southcentral,
especially over the Mat Valley. The winds (or lack thereof) will
continue to cause issues for temperature forecasts as well, with
mixing due to the winds keeping temperatures much warmer than
where the winds drop out during the next couple days.

&&

.AVIATION...
PANC...Strong and gusty northerly winds will weaken throughout
the day today a upper level winds become more easterly with time.
The veering of winds aloft should slowly push the core of
strongest northerly winds off to the west, allowing winds to
diminish at the terminal by this afternoon. Weaker north to
northeast winds gusting to around 20 kts may still persist
thereafter and linger into Tuesday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 2:
Today through Tuesday night)...

Strong gap winds will persist through today due to a tight
pressure gradient between high pressure over the interior of the
state and a surface low situated near the Alaska Panhandle. These
winds are expected to slowly diminish from their peak yesterday
as the cold air advection that was driving and enhancing these
wind gusts subsides. A weak easterly wave in the mid levels of
the atmosphere will move across Southcentral today. This feature
may help to not only maintain an east-northeasterly pressure
gradient across the Matanuska Valley, but help increase
atmospheric instability. This could allow winds to remain near
warning levels through at least the morning hours. Thus, the High
Wind Warning for the Matanuska Valley has been extended through
Monday afternoon. Elsewhere, winds are beginning to diminish
across the northern portions of the Anchorage Bowl. While there
may be a secondary peak in gusty winds later this morning, these
gusts are not expected to be as strong as those yesterday evening.
Furthermore, the aforementioned wave may shift the pressure
gradient enough to keep any area of gusty winds west of Anchorage
and out over Cook Inlet.

Dangerously cold wind chills will also continue across parts of
Southcentral through at least Monday. Values ranging from 45 to 55
below zero are possible for Thompson Pass and Broad Pass, with
valley locations seeing values as low 10 to 30 below zero.

While clear and cold conditions prevail across the Southern
Mainland, clouds and periods of light snow will be likely for
Kodiak Island today and Tuesday as a series of troughs moves from
the eastern Gulf to the western Gulf.

Heavy freezing spray will continue across much of the coastal
waters through the next couple of days.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: Today
through Wednesday)...

Strong northerly flow aloft continues across the region, bringing
clear, cold and dry conditions. Wind Chill Advisories remain in
effect for the Middle Kuskokwim Valley and central Bristol Bay.
The strongest core of winds have shifted northward and are now
found over the Kuskokwim Delta. Winds will gradually diminish and
veer easterly Tuesday into Wednesday, though temperatures will
remain below zero over the interior. No precipitation is
expected.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3: Today
through Wednesday)...

Strong northerly winds remain possible this morning as a result of
impressive forcing between an upper low in the Gulf and a ridge
over the central Bering. Conditions will be much more quiet over
the Pribilofs and central/western Aleutians closer to the ridge
axis. The aforementioned upper low will flatten and track westward
late tonight through Tuesday. Surface winds will diminish and
shift more easterly. Light snow or mixed precipitation will be
widespread across the Aleutian Chain, likely changing to all rain
by Wednesday as upper flow becomes more southerly.

&&

.MARINE (Days 3 through 5/Wednesday through Friday)...

Bering/Aleutians...

Forecast confidence remains above average during the 3-5 day
period. Widespread easterly gale force winds are expected across
the southern Bering Sea on Wednesday. These winds ease to below
gale force on Thursday and back northeasterly on Friday. There is
a high probability of heavy freezing spray across the ice free
waters on Friday. These winds will allow for large long period
swell to build in the western Bering Sea on Thursday due to the
long fetch over the water. This swell will then gradually abate on
Friday.

Gulf of Alaska...

Forecast confidence remains above average with widespread strong
easterly winds that are likely to reach gale force across the
southwestern Gulf. These winds will then weaken to below gale
force on Thursday and remain below gale force on Friday.

&&

.LONG TERM FORECAST (Days 4 through 7/Thursday through Sunday)...

The pattern will remain amplified during the extended period as
the Aleutian Low will deepen across the eastern Aleutians while
upper ridging extends across Siberia. This will allow for brisk
easterly winds across the Bering Sea to back northeasterly Friday
night. These strong northeasterly winds will allow for convective
snow showers across the Aleutians and is likely to result in heavy
freezing spray in the ice free waters. This pattern will also
allow for the cold temperatures to continue across Southcentral
and Southwest Alaska as offshore flow continues on Thursday and
Friday. Precipitation chances will increase this weekend,
especially for coastal areas along the northern Gulf as the flow
pattern will shift from offshore to onshore as the Aleutian Low
deepens. This will be an interesting pattern as pressure gradients
(ageostrophic flow) support an offshore surface wind flow pattern
across the leeward locations while the geostrophic flow will
favor an onshore surface wind flow across windward locations.
This will allow for precipitation across coastal areas such as the
southern Kenai Peninsula and Prince William Sound. There is a
chance for intermittent snow in the Anchorage Bowl Saturday
afternoon through Sunday afternoon as there is good model
agreement for weak cross barrier flow across the Chugach
Mountains. The weak cross barrier flow will allow for minimal
downsloping and thus increase the chance for precipitation.
Temperatures in the lower levels of the atmosphere will be
conducive to snow as the dominant precipitation type in the
Anchorage Bowl this weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning: 111, 181.
         Blizzard Warning: 141.
         Wind Chill Advisory: 141, 131, 145, 161, 152.
MARINE...Storm Warning: 150,155.
         Gale Warning: 119,125-128,130,132,138,139,140,160-185.
         Heavy Freezing Spray: 119-131,136-139,141,150-165,179,
         180,185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AS
SOUTHCENTRAL ALASKA...TM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AP
MARINE/LONG TERM...ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
151 PM AKST MON JAN 3 2022

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

0210 AM     EXTR WIND CHILL  9 ENE MENDELTNA         62.10N 146.17W
01/03/2022  E-50 F           VALDEZ-CORDOVA     AK   PUBLIC

0453 AM     EXTR WIND CHILL  7 NE GLENNALLEN         62.15N 145.45W
01/03/2022  E-55 F           VALDEZ-CORDOVA     AK   ASOS

1120 AM     EXTR WIND CHILL  4 NNE CHITINA           61.58N 144.43W
01/03/2022  E-50 F           VALDEZ-CORDOVA     AK   OTHER FEDERAL

0211 AM     NON-TSTM WND GST 1 S TALKEETNA           62.32N 150.09W
01/03/2022  E59 MPH          MATANUSKA-SUSITNA  AK   ASOS

0236 AM     NON-TSTM WND GST 1 E PALMER              61.60N 149.09W
01/03/2022  E87 MPH          MATANUSKA-SUSITNA  AK   PUBLIC

0322 AM     NON-TSTM WND GST 3 ENE SUTTON            61.74N 148.79W
01/03/2022  E60 MPH          MATANUSKA-SUSITNA  AK   PUBLIC

0334 AM     EXTR WIND CHILL  20 WSW CANTWELL         63.30N 149.54W
01/03/2022  E-51 F           MATANUSKA-SUSITNA  AK   OTHER FEDERAL

0556 AM     EXTR WIND CHILL  25 WSW MENDELTNA        61.93N 147.17W
01/03/2022  E-41 F           MATANUSKA-SUSITNA  AK   AWOS

0131 PM     EXTR WIND CHILL  5 E CHICKALOON          61.81N 148.33W
01/03/2022  E-49 F           MATANUSKA-SUSITNA  AK   OTHER FEDERAL

&&