High Wind in Alaska, November 7, 2022

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
448 PM AKST Sun Nov 6 2022

.ANALYSIS AND UPPER LEVELS...
A high amplitude upper level ridge extends out of the North
Pacific and over Southwest mainland Alaska. This is continuing to
cause northerly flow aloft over Southcentral Alaska though the
upper level winds are not making it down to the surface and
therefore winds are not nearly as strong as yesterday.
In Southwest mainland Alaska, the high level cirrus is already
over most of the region early this afternoon and the pattern
change is beginning. The surface low is still over the Central
Aleutians with the front now bringing rain to the Pribilof
Islands and reaching the western part of the Alaska Peninsula.
There is quite a bit of warm air with this system and it will
bring a mixture of precipitation types to Southwest Alaska as it
moves through.

&&

.MODEL DISCUSSION...
The same model issues remain as were discussed in previous
forecasts. The GFS is the quickest to develop a secondary low
south of the Kenai Peninsula and therefore keeps the warmer air on
Monday and Tuesday farther south. The ECMWF and NAM are delayed
in doing so which allows more warm air to the north Gulf coast
and then into the Cook Inlet region. This is a key feature
regarding precipitation type, amount and winds especially for the
Cook Inlet area. Even during the mid-week period, the ECMWF is
injecting more warm air toward the interior of SOuthcentral than
the GFS which keeps the region cooler. That said, all the models
show a considerable warm up for all of Southern Alaska for the
mid week into next weekend period.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist through Monday
morning. There is a chance for some light snow and MVFR conditions
Monday evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 to 3)...

Dry weather will continue through tonight for most of
Southcentral. Although winds through Whittier and Valdez areas
have been lingering due to cold and gusty gap flow, they are
trending down and should continue to diminish for the rest
tonight. High clouds are beginning to filter into Southcentral
ahead of a frontal system expected to move from west to east
Monday.

Precipitation chances are expected to increase for Kodiak
beginning Monday morning. With strong south to southeasterly flow
accompanying the front, any snow in Kodiak will be brief and
quickly turn to rain where highs will also reach the lower 40s. As
precipitation sweeps eastward, chances increase for the Homer and
Seward areas of the Kenai Peninsula late Monday morning. By
Monday afternoon, northwestern Kenai and the Anchorage Hillside
could see light snow Monday afternoon as cold air remains in place
and the warm up is more gradual. There will be some degree of
downsloping expected for the western Kenai, Anchorage bowl, north
to the Matanuska Valley that will keep precipitation light. The
onset along with the timing of the precipitation type transitions
and any downsloping has presented a continual forecast challenge.
While there is high confidence with the initial onset of the
frontal passage, a surface low development which follows in the
western Gulf has model uncertainty that is playing a role with the
forecast outcome. NAM is quite aggressive with warm air mixing
out of the Kenai Peninsula much sooner than the GFS, whose low is
also remaining more south. As the low progresses east however,
warmer air will continue to move northward and temperatures should
continue to trend slightly warmer Tuesday and Wednesday
afternoon. The majority of the Susitna Valley and Copper River
Basin should remain cold enough for the first half of the week to
remain snow.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

A ridge of high pressure will slowly shift east tonight in
response to a North Pacific low lifting north in the Bering Sea.
Ahead of the low, a strong front is on track to move eastward
toward western Alaska. Gusty southeasterly winds along the front
will start to increase especially along the coastline. Because of
a high tide cycle and minor inundation, a Coastal Flood Advisory
was issued for areas west of the Kuskokwim River Mouth for Monday
morning and afternoon. Moreover, winds funneling through Kamishak
gap will also increase for the eastern corridor of Bristol Bay,
including Koliganek and New Stuyahok, before subsiding Monday
night.

As far as precipitation concerns, the main impacts will be heavy
wet snowfall combined with strong winds reducing visibilities in
Bristol Bay around the same time. A Winter Weather Advisory was
issued to highlight these impacts, with total snow accumulations
between 4 to 8 inches for this region. For the Kuskokwim Delta and
Kuskokwim Valley, light snow amounts are expected on Monday with
southeasterly winds downsloping most of the precipitation.

Warmer air will help transition precipitation type quickly to all
rain for rest of day on Monday. Daytime temperatures are expected
to climb in the upper 30s to low 40s with overnight temperatures
near freezing. The front exits the area overnight Monday with a
brief break of drier early Tuesday. A developing low pressure
system in the North Pacific moves toward the western Gulf of
Alaska. There are positional differences with this system, but a
likely scenario is unsettled conditions continuing through
midweek.

&&

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

A North Pacific low is on track to lift north of Atka tonight.
Ahead of the low is a front bringing moderate to heavy rain and
storm force southerly winds through the central/eastern Aleutians.
Seas above 20 feet are also expected south of the Chain between
tonight and Monday. As the low occludes and then tracks in the
Bering Strait on Monday, the strongest winds will gradually shift
toward the eastern Bering Sea and western Alaska. Winds will
subside with rain slowly tapering by Tuesday. A general troughing
pattern will likely persist through midweek with a series of weak
systems traversing across the Bering/Aleutians.

&&

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

Similar to the past day or so, model agreement starts out very
good at the start of the period on Thursday, but solutions again
diverge significantly heading towards the weekend. To start things
off on Thursday, three synoptic systems will be in play looking
from east to west across the outlook area. On the east side, an
upper trough and and attendant surface low will be drifting east
across the Gulf, focusing areas of rain and snow across
Southcentral on Thursday predominantly along the northern Gulf
coast. The second system will be a large gale to low-end storm
force low moving along or just south of the Aleutians, sending
gusty easterly winds and mainly rain across the Aleutian Chain
through at early Friday. The third system will be approaching the
western Bering by Thursday afternoon as it progresses east out of
Kamchatka.

As alluded to above, the finer scale details of the pattern begin
to blur looking from Friday onwards. The GFS has been a stubborn
outlier with the track of the larger, stronger low moving south of
the Aleutians compared to other solutions by Friday, with recent
runs still attempting to push most of the low straight east and to
the south of the Gulf as the entire system begins to weaken and
fill in. Both of the other global model solutions show the low
pivot more northeast, or straight into the central/eastern Bering
before stalling out in place through at least Saturday. These
differences significantly affect the potential wind field across
the Bering, while also playing a role in how the next item of
interest evolves towards the end of the forecast period.

The signal for a strong, blocking ridge to develop by Saturday
and Sunday is getting quite a bit stronger in today's model runs.
Both ensemble guidance and operational solutions are better honing
in on the potential for an Omega block ridge to develop over
Alaska and northwest Canadian provinces next weekend, while a
longwave trough stalls out to the west over the Bering and
Aleutians. This is increasing confidence for an extension into at
least Sunday of the already warmer than average temperatures
returning earlier on in the week across the southern mainland. The
most favored area for heavier precipitation with this pattern
developing will be focused over Southwest and along the Alaska
Peninsula, where strong southerly flow and moisture will stream
north between the Bering trough and blocking ridge to the east,
with mixed precipitation likely persisting across this area for
multiple days towards the end of this week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...VR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MF
LONG TERM...AS