Gale Warning 74, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
552 PM AKST Sat Jan 18 2025

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

A fairly strong frontal system now entering the southwestern Gulf
remains the primary driver of impactful weather across
Southcentral Alaska through early Monday. This system is
encountering a sharp and amplified ridge axis extending from the
eastern Gulf into the eastern Mainland, which is gradually
shifting east into Canada. The slower progression of the trough
has allowed for the development of a low-pressure system over the
northern Gulf and southern Prince William Sound, which, combined
with the advancing front, is expected to enhance precipitation and
wind across the region.

Ahead of the main frontal system, light precipitation has
developed along the coastal mountains due to upslope flow from
southeasterly winds. Model guidance has exhibited a wet bias in
areas where precipitation is primarily driven by upsloping flow.
However, stronger forcing and dynamic lift will arrive tonight
into early Sunday as the frontal wave lifts northward, bringing an
increase in precipitation rates particularly around the Prince
William Sound and the surrounding mountain ranges.

A Winter Weather Advisory is in effect for Turnagain Pass from 6
PM this evening through midnight Sunday night where 12 to 20
inches of heavy snow are forecasted with snowfall rates of over 1
inch per hour are possible. An advisory is also in effect for
Thompson Pass from midnight tonight through 9 AM Monday where 20
to 30 inches of heavy snow are expected.

A deformation band is expected to develop over the western Kenai
Peninsula, slowly pushing eastward into Anchorage and the Mat-Su
Valley into Sunday night. While the primary energy and moisture
will remain over the Gulf, this band may bring a period of
moderate to heavy precipitation, including the potential for
heavy, wet snow in localized areas. Accumulations in lower
elevations will likely be minor, with surface temperatures near or
above freezing. However, the northern Susitna Valley and Hatcher
Pass could see several inches of snow due to enhanced
precipitation from south to southwesterly upslope flow.
Additionally, snow totals of several inches are expected in Paxson
and Isabel Pass under similar conditions.

Easterly winds will increase late tonight across the Anchorage
Hillside, Turnagain Arm, and Portage Valley as the system
approaches. Sustained winds of 25 to 35 mph with gusts of 45 to 60
mph are forecasted in Portage Valley and Turnagain Arm, with even
stronger gusts of 60 to 80 mph possible along the Upper Anchorage
Hillside, including Bear Valley and Upper Potter Valley. These
winds will peak through mid to late Sunday morning before
gradually tapering off by late Sunday afternoon.

Precipitation and winds across Southcentral will begin to
diminish late Sunday night into Monday morning as the trough exits
eastward into the Copper Basin. A brief shortwave ridge will
follow on Tuesday morning, providing a short-lived break in the
weather. However, another frontal system is expected to approach
the region late Tuesday into Wednesday, bringing the potential for
renewed precipitation and wind impacts.

Eovino

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Saturday afternoon to Tuesday afternoon)...

A compact surface low is currently crossing the Alaska Peninsula
(AKPEN), aiding in the continuation of winds and precipitation to
Southwest. Moderate to heavy snow will fall at higher elevations
of the Aleutian Range and Wood River mountains, while light rain
more showery in nature is expected for the rest of the region.

A low pressure system moving in from the North Pacific will begin
to impact the Aleutians tomorrow morning as the low center tracks
just south of the Aleutian Chain, enhancing winds and precip as
shortwave troughs spin up into the Bering Sea. This pattern is a
good setup for a potential blowing snow event for the Pribilof
Islands and Nunivak Island Monday into Tuesday. Models are not in
very good agreement as to the exact track, bringing some
uncertainty in timing and intensity. We will continue to monitor
this closely.

The front associated with this system will bring gale-force winds
and moderate precip Monday and Tuesday as it marches eastward up
the AKPEN and into the Bristol Bay Region. Mixed rain and snow is
expected for more inland locations before a transition to all
rain on Tuesday as southerly flow continues to bring in warm air.

&&

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

The active weather pattern over Alaska will continue as a number
of upper level shortwaves rotate across the region through the
forecast period. Late in the week, additional energy from a
transient North Pacific low will add to the movement.

Some lingering areas of rain moving across the southcentral
coasts Wednesday will have a brief reprieve Thursday. The next low
brings locally heavy rain, or a rain and snow mix spreading
across southwest Alaska, the northern AKPEN and Kodiak Island for
Friday, with rain and snow moving into the Kenai and south central
Alaska for Saturday.

&&

Baker

.AVIATION...

PANC...Light north to northwesterly winds at the surface with
southeasterly winds of 30-40 kt at or above 1500 ft will
contribute to continued low-level wind shear through Sunday
afternoon. Current VFR ceilings of 15-20 kft will begin to lower
to under 10 kft Saturday night and then to low VFR by Sunday
morning. A short period of precipitation is likely to push through
the terminal Sunday afternoon/evening. Visibility and ceilings
may drop as low as IFR for a few hours if precipitation falls as
snow before improving back to VFR in the late evening as a light
southeasterly wind kicks in behind the front.

&&