Gale Warning 159, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
412 PM AKST Mon Feb 5 2024

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

A negatively-tilted upper shortwave is now lifting up from the
Alaska Peninsula and Kodiak Island into the Kenai Peninsula and
Cook Inlet region as a shortwave ridge positioned over
Southcentral begins to move off towards the Yukon. A surface low
supported by this trough is now clearly visible on GOES West
satellite imagery over the northern Gulf, about halfway in between
Seward and Kodiak. Areas of light snow over land and mostly rain
over water are continuing to affect parts of the Kenai Peninsula
and Prince William Sound north and west of the small Gulf low as
it drifts steadily east. Out towards the Mat Valley down into
Anchorage, snow is not reaching the ground thanks to southeasterly
and cross- barrier flow out ahead of the approaching trough.
However, there still will be a short window for light snow to fill
in this evening into tonight as the low moves out towards
Middleton Island and as southeast flow shuts off. Even still,
forcing and moisture with this setup look unimpressive, and it
will be tough to squeeze out more than a half inch of snow at most
across the Anchorage Bowl and Mat-Su Valleys before the shortwave
lifts into the Copper Basin by Tuesday morning.

A fairly benign pattern still looks on track for much of the
remainder of the short range as a trend toward more seasonable
temperatures in the 10s to 20s further solidifies. A narrow but
rather strong shortwave ridge axis will build back into
Southcentral behind the system exiting to our east on Tuesday,
promoting dry conditions for nearly the whole outlook area.
Between Tuesday night and Wednesday, a strong low in the Bering
Sea will push another weakening front first across Kodiak Island
from the west, then up into the southern Cook Inlet and Kenai
Peninsula. This front looks even less impressive than the past two
systems affecting parts of Southcentral, and it looks unlikely
for rain and snow with this decaying system to reach beyond Homer
and Seward as it begins to stall out in the western Gulf on
Wednesday. Yet another new low formation at the frontal triple
point is likely over the central Gulf by Wednesday afternoon, but
this new low will track far enough south to again keep the bulk
of precipitation focused from the eastern Kenai Peninsula and
south over open water.

By Thursday, another rapidly building ridge will spread back over
the Gulf and southern Mainland ahead of a more potent looking
North Pacific low approaching the southern Alaska Peninsula from
the south. This system's front could push more widespread
rain/snow and gusty east winds into parts of Southcentral towards
the end of the week.

- AS

&&

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

Key Points:

* A High Wind Warning has been issued from 3 AM Tuesday Morning to
  3 PM Tuesday Afternoon for the Alaska Peninsula and Eastern
  Aleutians including  Cold Bay, Sand Point, Unalaska, Nikolski
  and Dutch Harbor. Expect Southeast winds becoming south and then
  Southwest in the 40 to 60 range. Wind gusts to 75 mph are
  expected.

* The strong low pressure system continues to move north out of
  the Northern Pacific into the Southern Bering Sea on Tuesday
  morning and north of the St Matthew Island by Tuesday afternoon
  with gales and storm force winds spreading north into the
  Central Bering Sea and along the Southwest Coast on Tuesday.
  Expect mainly snow and blowing snow north Dillingham with mixed
  rain and snow to the south.

Discussion:

Ongoing forecast with a strong storm moving north out of the
northern Pacific into the Southern Bering Sea Tuesday Morning
continues to be on track on timing and very similar on track,
however latest guidance has continues to deepen the low as it
moves north into the Southern Bering Sea. As was the case with
last nights forecast package, today's forecast package was updated
with stronger winds with High Wind Warnings being issued for the
Alaska Peninsula and the Eastern Aleutians where wind gusts of 75
mph are expected beginning around 3 AM Tuesday morning and
continuing to around 3 PM on Tuesday afternoon. Highest confidence
of 75 mph or greater winds will be in Cold Bay and Dutch Harbor
with terrain channeling increasing winds gusts. We will continue
to monitor the potential for strong winds along the Western Capes
of Bristol Bay, and Kuskokwim Delta. Southerly flow and warm air
advection will also lead to some question about precipitation type
and the potential for blowing snow especially in areas north of
Dillingham where precipitation is expected to remain all snow.
Areas to the south including Bristol Bay, the Eastern Alaska
Peninsula, and the Eastern Aleutians will likely see very wet snow
or a mix of rain and snow which will limit blowing snow
potential. Please stay tuned as we continue to refine the
forecast.

- CC

&&

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

Friday morning an upper level low is centered over Bristol Bay
moving northward. Model agreement is poor concerning the track of
this low. The GFS depicting the most westward track which would
take it offshore and parallel to the western Alaskan coast. The
Canadian and European models depict tracks over the Southwestern
mainland. Shortwave troughs from this low push gale force winds
across the Gulf and bring precipitation to the northern Gulf coast
through Saturday afternoon. Sunday morning, two upper-level North
Pacific lows enter the forecast area. One passes over Adak on its
way into the Bering Sea, and the other moves north through the
Gulf of Alaska.

&&

.AVIATION...

PANC...A weak front will be in the area into the early overnight
period. Modest downsloping has kept precip out of ANC for much of
the day, but confidence has increased that some light snow will
make it to the ground this evening. CIGs and VIS should be in the
MVFR and VFR range, with only a low probability of IFR conditions.

Wind will remain light and generally under 10kt through the TAF
period.

&&