Gale Warning 351, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
359 PM AKDT Sat May 3 2025

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

This afternoon, an occluded surface low is dissipating in Prince
William Sound as weak surface ridging tries to build in its wake.
All that is left of the low is a low to mid cloud swirl and a band
of rain situated over Cordova and Valdez. Temperatures in the
Western Kenai Peninsula, Mat-Su Valley, and Copper River Basin
have warmed into the low 50s today, while higher elevations have
warmed into the mid 40s. The surface warming and trough has added
instability for lower elevations this afternoon for convective
showers and thundershowers to form, particularly from Eagle River
into the Mat-Su Valleys, northwest Kenai Peninsula and portions
of the Copper River Basin. The limiting factor to convection today
is specifically for Anchorage and immediate surrounding areas to
the south and west where a capping inversion has held on since
this morning, which has caused mainly dry conditions with any
convection forming this afternoon to be weaker and elevated. Some
nearby areas are also experiencing a seabreeze, and for this time
of year, flow off of the Inlet is quite cool.

Due to the orientation of the low and trough envelope, some gap
winds have kicked in as well in typical locations, especially for
the Turnagain Arm where the up-inlet gradient is causing these
winds to bend into the Anchorage bowl. Winds will begin to
diminish Sunday morning due to the trough passage and the flow
flipping to down-inlet as a secondary large and potent frontal low
pressure system approaches Kodiak Island.

By Sunday afternoon, the front drives into the Southcentral
coast, forcing heavy precipitation and a strong barrier jet along
the coastline. Inland areas will be sheltered from most
precipitation due to downsloping and will see lower precipitation
chances. Once again, higher elevations generally above 2500 ft
could see snowfall, especially at night. Winds will be greatly
enhanced as well from this front. Inland, gap wind locations such
as the Turnagain Arm and to a lesser extent, the Knik Arm, again
pick up Sunday afternoon, but the Turnagain wind will be
redirected away from the Anchorage bowl as the flow will likely be
down-inlet. By Sunday afternoon, winds will have increased to
storm force along the front near the Barren Islands, with high end
gale force winds over the northern Gulf and increasing to storm-
force south of Prince William Sound. Hurricane force wind gusts
cannot be ruled out (64 kts or greater).

The barrier jet quickly collapses with the frontal passage during
Monday morning as an onslaught of heavy precipitation overwhelms
the immediate Southcentral coastal areas. QPF amounts will likely
be impressive with this system, with 2 to 3"+ of rainfall
possible for much of the coastline and areas that benefit from
orographic lift, such as along the southern facing slopes of the
Chugach and eastern facing slopes of the Kenai Mountains.
Conditions will most likely slowly improve during the day and
afternoon hours of Tuesday, with the sprawling attendant area of
low pressure still spinning in the Southern Gulf.

-AM/TM

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Monday night)...

Currently, a region of high pressure is over the Southwest Alaska
mainland. This is allowing for calm winds. There are some areas
of low stratus and fog along the coast. Some isolated showers are
occurring north of Dillingham. The Bering is seeing gusty
northerly winds and some precipitation in the Aleutians due to a
surface low south of the Eastern Aleutians. These conditions will
linger through the rest of today (Saturday). The low will set the
stage for weather for the next few days in Southwest Alaska.

By Sunday, the low will migrate eastward and situate itself near
Kodiak Island by Monday, where it becomes quasi-stationary. The
low will also grow in strength and size before it reaches this
point. The low will bring northerly gale force gap winds in the
Eastern Aleutians and Alaska Peninsula regions. This will be aided
by a persistent tongue of cold air that stretches down from the
north. The low will also drive up precipitation chances in Bristol
Bay and the Alaska Peninsula. The Kuskokwim Delta will see lower
chances of precipitation due to downsloping easterly winds.
Speaking of easterly winds, they will cause strong winds to flow
out of the Kamishak Gap, driving into Dillingham by Sunday
afternoon. As the low stalls near Kodiak Island, expect the
precipitation to linger in the Bristol Bay region through Tuesday
morning. The Eastern Aleutians and parts of the Alaska Peninsula
could also see snowfall through Tuesday as cold air advection from
the north persists. Winds will become lighter in both the
mainland and the Eastern Aleutians on Monday as the winds change
in orientation and the low weakens. Over the Lower Kuskokwim
Valley, instability increases Monday and Tuesday. This, combined
with a couple of shortwaves from the low will allow for a
potential of isolated thunderstorms Monday afternoon and Tuesday
afternoon.

The western Aleutians will see a ridge move in on Monday,
limiting chances for precipitation and changing winds to southerly.
The southerly winds will also allow for warm air advection to
take place. The ridge gradually flattens as a low pushes in from
the west on Tuesday. The low's front will bring a burst of
precipitation and higher wind speeds to the western Aleutians by
Tuesday morning.

-JAR

&&

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

Wednesday, a weakening low sits in the southern Gulf with an
occluded front wrapped around the Gulf coast. With a high
amplitude ridge building across northwestern Canada, the upper
level low will linger over the Gulf through Friday. Shortwaves
rotating around the low center may lead to development of multiple
additional surface lows, but all of them will ultimately end up
tracking to the position of the upper center. The most impacted
areas will be along the Gulf coast and Kodiak Island, with
occasional rain or rain showers. None of the surface lows look
particularly strong, so winds for the Gulf coastal waters look to
remain at or below Small Craft Advisory levels. For Southcentral
and Southwest AK, this pattern will bring a mix of sun and clouds,
with some weak ridging at times but also the likelihood of upper
level shortwaves rotating through with some clouds and showers.

Meanwhile, a deep low will track into the far western Bering Sea
Thursday, with a leading frontal system progressing eastward
across the Bering and Aleutians. The GFS and Canadian models
indicate this low exiting into the North Pacific by Saturday, but
these might be outliers as ensembles depict the surface low
remaining in the central Bering through the weekend. In either
case, expect low impact weather for the Bering and Aleutians next
weekend.

&&

.AVIATION...

PANC...VFR conditions will persist. Some southeasterly Turnagain
Arm winds are expected over the terminal again this afternoon into
the overnight hours. While the mid and upper levels of the
atmosphere are unstable today, the more stable lower atmosphere in
conjunction with the gusty southeasterly winds should keep shower
activity away from the airport though it may occur over the
mountains and on the far side of Turnagain Arm and Knik Arm
through this evening.

&&