Small Craft Advisory 36, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
531 AM AKST Tue Jan 10 2023

.ANALYSIS AND UPPER LEVELS...

A surface low is crossing the Alaska Peninsula early this morning
into Bristol Bay bringing precipitation across Southwestern
Alaska. Snowfall is being reported in Dillingham north to Bethel
and on and off snow showers further inland toward the Middle
Kuskokwim Valley. Warmer surface temperatures are further south
near King Salmon and Iliamna, in the upper 30s and 40s. There is
cloud cover through there, but precipitation is scoured out
through downsloping. Closer to the low center, Port Heiden is
below freezing and snow, while Pilot Point is above and dry.

Southerly flow is moving through Southcentral with just enough
energy ahead of trough to bring periods of precipitation to
southern and eastern Kenai Peninsula. Precipitation could become
more steady as a band of precipitation, seen on Middleton radar
pushes northwestward. On the edge of the shroud of clouds, the
Glennallen area from south of Chistochina to Kenny Lake has fog.

Cool temperatures over the Aleutians with narrow bands of snow
showers to the far west.

&&

.MODEL DISCUSSION...

Models are in reasonably good agreement when considering trends
and over all synoptic patterns and weather expected through most
of this week. There were some discrepancies in earlier models
runs with the global versus HiRes models on whether portions of
the western Kenai Peninsula and Anchorage could expect a wave of
light snow Tuesday night into Wednesday or be completely
downsloped. Global models overnight are nudging into agreement
with HiRes for early Wednesday morning. There are also slight
differences in the timing of precipitation as it spreads east.
Model agreement breaks down substantially at the end of the week
as the storm force low in the western Bering degrades and the
potential for trough new development somewhere near the Aleutians
and also the Gulf coast.

&&

.AVIATION...
PANC...VFR conditions early with northerly surface winds
expected. Southeasterly winds aloft could lead to a marginal
chance for low level windshear in the vicinity Tuesday afternoon
through the evening ahead of a front that could lower cloud bases
and bring a chance of light snow around midnight through Wednesday
morning.

&&

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

Another shortwave trough will bring a shot of precipitation to
Southcentral. This morning rain and snow showers are expected
across Kodiak Island with minor accumulations. Across the Kenai
Peninsula snow is expected to increase across the eastern part of
the Peninsula today and then spread across Homer this afternoon
and northward towards Kenai and Soldotna into the evening and
night-time hours with less than an inch of snowfall expected.
This shortwave will continue to lift northward towards Anchorage
and the Mat-Su valleys tonight through Wednesday morning bringing
periods of light snow. Snowfall amounts will generally less than
an inch. Higher snowfall amounts are expected around Seward with
around 6 inches expected and up to a foot around Whittier and
Portage Valley, while Turnagain Pass and along the Seward Highway
2 to 6 inches of snow is expected. This shortwave will lift across
the interior of Southcentral on Wednesday bringing a brief period
of light snow across the Copper River Basin with little to no
accumulations expected. Wednesday night into Thursday a ridge
builds across the Gulf while another shortwave trough moves across
western Alaska towards the interior of Southcentral. However, as
the trough moves eastward into the area it weakens significantly
so it is uncertain if any snow will occur from Anchorage northward
across the Mat-Su valleys. Otherwise most of the rest of
Southcentral will remain dry except for a few lingering showers
across Kodiak Island and the eastern Kenai Peninsula.

&&

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

An upper low over the Alaska Peninsula is bringing light snow and
gusty winds to portions of Southwest Alaska this morning, mainly
across Bristol Bay to the north and northwest of Kvichak Bay.
Accumulations will be on the lighter side though Dillingham and
points northward could see storm total snow amounts of 4 to 6
inches through this afternoon. Snow is expected to taper off over
the latter half of the day as low pressure over the Alaska
Peninsula gradually shifts to the north of Bristol Bay and
weakens. This will allow for weak high pressure to overspread the
region with calmer and drier conditions Wednesday through Friday.
Over far eastern portions of interior Bristol Bay, easterly winds
downsloping over the Western Alaska Range have resulted in dry
conditions and warming temperatures into the upper 30's. King
Salmon managed to hit 40 degrees at around 3AM while Iliamna sits
at 38 degrees. Eastern parts of Bristol Bay will remain warmer
through tonight until easterly winds become westerly on Wednesday.

&&

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

Mostly benign conditions are ongoing across the Bering and the
Aleutians this morning as the region sits within a cull. This all
begins to change on Wednesday with the arrival of a large upper
low into the western Bering. This low will be accompanied by storm
force winds as a broad front overspreads the Western and Central
Aleutians Wednesday through Thursday. Strong southerly flow ahead
of the low and along the front combined with a moisture tap from
the North Pacific will see around an inch of precipitation fall in
across Adak and as far east as Atka. While highs are forecast to
warm into the upper 30's across the Central Aleutians on Wednesday
afternoon, several inches of snow will be possible Wednesday
morning before transitioning to all rain by Wednesday afternoon.
Numerical guidance is in good agreement with stalling the low over
the Western Aleutians by Thursday, with the Eastern Aleutians and
Pribilofs not expected to see any impacts from winds or
meaningful precipitation through Thursday.

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

A building ridge in eastern mainland Alaska will promote a stable
environment for Southcentral. Out west, a longwave trough will
make its way through the region, with several shortwaves and North
Pacific lows approaching the Bering. A shortwave trough
approaching coastal Southcentral Friday looks to promote
precipitation along the coast, but lacks the strength and
orientation to push inland. A drier pattern seems to emerge for
Southcentral and Southwest this weekend as shortwave passages drop
out and upper-level ridging builds. In the Bering, a low complex
in the Western Bering/North Pacific will draw multiple fronts and
low pressure systems into the Aleutians through the Weekend into
Monday. A low formed at the triple point of one such front looks
to approach the Southwestern Gulf of Alaska Monday morning.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 130, 139, 175, 176, 411, 413
		 Storm Warning: 177, 178
		 Heavy Freezing Spray Warning: 140, 180, 185, 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...VR
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BL
LONG TERM...CL