Gale Warning 670, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
436 PM AKST Sat Nov 12 2022

.ANALYSIS AND UPPER LEVELS...

Out west a broad area of low pressure is producing showers across
the Aleutians with winds generally less the 25 knots. A slow
southward moving cold front is draped across the Bering bringing
light snow along the Pribilofs. Across Southwest Alaska and the
AKPen a slow moving low pressure system near Bristol Bay is
producing rain and snow across the area as seen on radar, with
most of the snow in the higher elevations as temperatures near sea
level are in the mid to upper 30s. Across the Kuskokwim Delta
gusty northerly winds and areas of light snow have been observed,
with the strongest winds along the coast with 30 to 45 knots
reported. Across the Kuskokwim valley light snow has been observed
along a front that is pushing north. Across Southcentral a front
is pushing onshore and will usher in the Turnagain winds, Copper
River winds, and possibly the Knik winds. This front is producing
widespread rain along the coast with snow in the higher elevations
with the snow levels at 1500 to 2000 feet. Behind the front is a
shortwave that is producing another swath of precipitation across
the northern Gulf and towards the southern and eastern parts of
the Kenai Peninsula. Radar shows rain and snow from Prince William
Sound towards the eastern Kenai Peninsula. With another band of
light snow along the western Alaska range and southern Susitna
valley. Temperatures across Southcentral are in the 30s across
most inland areas with 40s near the coast. And 20s across the
Kuskokwim Delta and valley area with 30s across Bristol Bay, with
low 40s across the AKPen and Aleutians.

&&

.MODEL DISCUSSION...

Model are in good agreement with the main synoptic features.
There are still some timing and placement issues with the surface
low tracking northward near the Kenai Peninsula and towards
northern Cook Inlet and the Anchorage area on Sunday. Challenges
for this forecast continue to be precipitation type and
transitioning from one to another, especially for the Kenai
Peninsula, Anchorage, and the MATSU Valleys. Sunday will be
particularly challenging as winds turn northerly ahead of the
approaching low pressure system, which could draw down some cold
air and may bring periods of light snow on Sunday before changing
to either rain or a rain/snow mix across the Kenai Peninsula,
Anchorage and the MATSU Valleys.

&&

.AVIATION...

PANC...VFR conditions will prevail. Occasional MVFR ceilings are
possible this evening as a mix of rain and snow develops and again
tomorrow near mid-day through the afternoon. The Turnagain
southeasterly winds will kick in this afternoon and may gusts up
to 25 knots or so. Winds are expected to turn back to the north
tomorrow morning at 10 knots or less.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
A warm front is slowly lifting northward this evening with
continued widespread rain along the north gulf coasts. Southeast
Turnagain Arm and Knik Arm winds are ramping up in response to a
tightening pressure gradient. As a result, the Anchorage Bowl and
Mat Valley will mostly be dry with the downslope easterly flow,
but some wintry mix precipitation is possible tonight.

By Sunday morning, a North Pacific low moves into Kodiak Island
with another round of precipitation and wind across Southcentral.
Models are coming into a better agreement with this feature as it
will likely move between Cook Inlet and Prince William Sound
around Sunday afternoon and evening. A potent upper level
shortwave trough coupled with warm, moist southerly flow looks
favorable to bring additionally rain for Seward, Cordova, and
Valdez.

As the low moves inland, precipitation increases for the rest of
Southcentral between Sunday and Monday given the sufficient
dynamics in place and the lack of downsloping. The Anchorage Bowl
and Mat Valley may start out with a brief wintry mix in the
morning, but should quickly transition to all rain by early Sunday
afternoon as daytime temperatures are expected to rise in the
40s. The northern Susitna Valley will see less than 3 inches of
snow. Breezy conditions will be limited over the higher
elevations, but the core of strongest winds will be over the
coastal waters, especially along PWS and the Copper River Delta.

Precipitation tapers off by Monday afternoon as dynamics shift
east and drier air filters in. A ridge of high pressure builds
across the mainland state by midweek with quieter weather and
colder temperatures.

&&

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

Unsettled weather will continue through Sunday night. A surface
low located near the Bristol Bay region is responsible for
continuing snow and rain showers across the domain. Areas south
of the Kuskokwim Delta have reported rain this afternoon as the
aforementioned low drives warmer air into the area. An Arctic
trough situated over northern Alaska is influencing far enough
south to encompass the Kuskokwim region and is keeping the
precipitation all snow. Showers will persist over much of the
Southwest through Sunday night before a ridge of high pressure
pushes into the area, resulting in clearer and dryer conditions.
This will last mid-way through the week before more unsettled
weather makes its way back into the region.

&&

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

Low pressure stretches from the western to eastern Bering/Aleutians
with high pressure located in the northwestern portion of the
Bering. Showery conditions will persist beneath the low pressure
through Monday before it pushes into interior Bristol Bay and
dissipates. By late Sunday evening, the aforementioned high
pressure will track into the central Bering/Aleutians and will
continue to push eastward through the week. Meanwhile,
northeasterly small craft winds will continue across much of the
Bering through Sunday night, with a pocket of gale force winds
stretching from the Kuskokwim Delta coast to north of the Pribilof
Islands through Sunday evening. A Kamchatka low will track into
the western Bering Monday and will continue unsettled conditions
for the western Aleutians through at least Tuesday night.

&&

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

Looking ahead at the longterm forecast, a strong ridge builds
over the southern Mainland while a cutoff low lingers south of the
Gulf of Alaska. Benign conditions under the stagnant ridge and
across the southern Mainland are expected to persist into the
weekend though this pattern may lead to widespread fog at lower
elevations. Above average daytime highs and overnight lows are
also anticipated through the long term. There is average
confidence that a front may clip the north Gulf coast on Saturday
morning.

Out west, an upper-level trough and attendant surface low inhabit
the western Bering and Aleutians on Wednesday. However, decent
model spread still exists with the low track and strength which
will affect associated impacts. The GFS and Canadian solutions are
currently the strongest as they advertise winds up to storm force
between Shemya and Adak and over parts of the Bering. The
Canadian low is much quicker in lifting to the north to Russia
already by Wednesday morning, while the GFS low does not reach
Russia until Thursday. The EC is overall the slowest and weakest
solution as it produces only small crafts by the time it tracks
near Adak late Wednesday morning, weakening as it moves into the
Bering thereafter. Fortunately, there is better model agreement on
another low set to reach the western Aleutians for Friday and
Saturday. At this time, there is consensus between the GFS and
Canadian for widespread rain and gale force winds to accompany the
low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 119 120 125 131 179 180 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...MF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
LONG TERM...AF