Gale Warning 150, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
720 AM AKST Sat Feb 8 2025

.Update...

Pesky low level clouds are lingering across the southern Anchorage
metro this morning. This is causing some isolated foggy patches
where visibility is crashing to less than 1/4 mile. Early morning
satellite imagery is making it tough to distinguish. Normal tools
we use are obscured by a thin layer of cirrus clouds. As of 7a,
we are starting to see a clearer signal as the cirrus moves off.
Webcams around the area show most of the fog/low clouds hanging
around the base of the Chugach. From the Muldoon curves, south and
west towards Potter Marsh. The expansion west is limited and
decreases around the Minnesota curve. Midtown, downtown and along
the Glen, clouds are thin, but low and aren't nearly as
restrictive as they are south. Due to the isolated nature, will
hold off on any larger fog advisory for now. In this pattern, much
of this cloud cover will dissipate and move over Turnagain Arm as
the sun comes up.

-shea

&&

.PREV DISCUSSION... /issued 506 AM AKST Sat Feb 8 2025/

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

The ridge will continue to build across Southcentral through the
weekend. Winds remain light and skies are mostly clear this
morning. Over the Gulf, cumulus clouds and light showers were
spotted on radar and may continue through the rest of the weekend.
Meanwhile, a trough is moving from west to east across Kodiak
Island this morning. Precipitation is already reported in Akhiok.
Kodiak could start to see a mix of rain and snow or all rain by
noon.

The overall synoptic pattern is not expected to change much and
moisture flow will be directed from the south to southeasterly
direction through Kodiak and across Southwest Alaska. Another low
develops in the North Pacific as it lifts towards Kodiak and the
Alaska Peninsula, reinforcing additional rainfall to the area.
Across Kodiak, expect around an inch of rainfall each day this
weekend into next week. These amounts may vary slightly depending
on the orientation of the flow into Kodiak. By Monday, coastal
Kenai Peninsula and western Prince William Sound could see some
rain or snow showers with very light accumulation. The ridge will
be stubbornly in place and could dampen any precipitation chances
further east of Kodiak, with the pattern lingering into Tuesday.
By Wednesday, model consensus degrades but the ridge could be a
little more east, aligned with Alaska-Canada border.

rux

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

A blocking ridge of high pressure remains anchored over the
Southwest mainland and far-eastern Bering but is being nudged
slightly eastward as a large upper low over the western Aleutians
propagates north and east. This ridge has kept conditions stable
with clear skies, calm winds, and cool temperatures across
Southwest Alaska, with areas of low stratus persisting.

Attention then shifts to a rapidly intensifying North Pacific
low-pressure system, influenced by a large upper-level low off the
coast of the Kamchatka Peninsula. This upper-level low provides
the broader steering flow for the surface low, which is expected
to gradually rotate northward, drawing the occluded front into the
Aleutians by Sunday morning. The northward movement of the low is
enhanced by divergence in the left exit region of a very strong
200 kt zonal jet streak, which will also contribute to rapid
deepening, with central pressures expected to bottom out as low as
940 mb as it crosses the western Aleutians later on Sunday. Gale-
force winds will spread across the entire Bering and Aleutian
chain, extending to the Southwest Coastline through Monday.

As the system intensifies, a secondary 120 kt jet streak is
forecast to form downstream to the east of the low in response to
tightening thermal gradient downstream of the occlusion, in turn
amplifying the pressure gradients and enhancing the low-level jet
(LLJ) across the eastern Bering Sea and into Bristol Bay by Monday
morning. The GFS, being the strongest solution, forecasts an
80-90kt LLJ, although it is more robust than the ECMWF and NAM.
Regardless, storm-force winds remain possible, but wind gusts of
50 to 60 mph, particularly over Bristol Bay and the Alaska
Peninsula, and potentially the eastern Aleutians and Kuskokwim
Delta coast as well, remain likely.

The low will also interact with significant moisture advection,
with high integrated vapor transport (IVT) values supporting
widespread precipitation along the occluded front. However, the
front’s relatively fast progression will limit precipitation
amounts across the eastern Aleutians to around or just over an
inch, particularly from Unalaska to Sand Point, with higher
amounts over the southern AKPEN. The front begins to fall apart
before reaching the Southwest Alaska coast, weakening under the
influence of the ridge, with only the far western Kuskokwim Delta,
Nunivak Island, and the western capes of Bristol Bay seeing any
precipitation. Precipitation will start as a mix of rain and snow
before transitioning to all rain by Sunday afternoon, with a brief
period of freezing rain possible in interior Bristol Bay and the
Kuskokwim Delta Saturday night.

While coastal flooding remains a concern, extensive shorefast ice
and near-total ice coverage in Kuskokwim Bay will likely mitigate
impacts that could otherwise contribute to flooding. The low will
continue its progression toward the Kamchatka Peninsula by late
Monday, leaving the blocking ridge in place but slightly displaced
eastward.

Eovino

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

Significant changes are expected over the Alaska Weather Map
through the forecast period. While most of the active weather
events continue to occur over the Aleutians and Bering, the upper
level ridge that held station with quiet weather over Mainland
Alaska is drifting into the Arctic. This allows an upper level
trough to extend from Western Canada over the Southern two-thirds
of Interior Alaska and sets up the formation of an upper level low
by Friday. The expansive upper low and trough over the Aleutians
and Bering continues to weaken, relaxing the synoptic gradient
across the Alaskan domain, which allows some North Pacific
influence to enter the region. The ECMWF / GFS / Canadian models
that carried the features yields to an ensemble mix by the end of
the forecast period.

A well developed Western Bering surface low weakens and withdraws
into Siberia. Its decaying front extends across the Northern
Bering to Southwest Alaska with locally moderate rain and gusty
winds through late Tuesday. A low moving along the front in the
North Pacific dissipates over the Alaska Peninsula Wednesday.
Locally heavy rain is expected over most of the AKPEN and Kodiak
Island through late Tuesday. Areas of snow develop over Southwest
Alaska and the Northern AKPEN through Friday. Weak lows quickly
develop and dissipate over the Western Aleutians and Southcentral
coast, spreading showers through Friday.

- KZ

AVIATION...

PANC...VFR conditions and light winds will persist. The
development of vicinity fog is possible through the morning hours.

BL

&&