Gale Warning 351, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 AM AKDT Sun May 7 2023

.ANALYSIS AND UPPER LEVELS...

An upper-level low continues moving eastward over the western
Aleutians and western Bering Sea this morning. The associated
surface low is beginning to move into the central Bering while the
front sweeps across the central and eastern Aleutians this
morning. A tall upper-level ridge extends northward over the
eastern Bering Sea, the Pribilof Islands, and the southern Alaska
Peninsula as it moves slowly eastward towards mainland Southwest
Alaska. Meanwhile, the omega-like pattern continues with an upper-
level low east of the aforementioned ridge over Bristol Bay. This
upper- level low is lifting weak shortwaves northward through the
Gulf of Alaska to mainland Southcentral Alaska this morning. A
weak surface low pressure near Kodiak Island is helping to focus
shower activity around the eastern Kenai Peninsula where Homer
reports light rain along with low clouds. Weak shortwaves also
continue moving slowly westward through Bristol Bay around the
upper low. King Salmon Radar shows very light precipitation from
roughly Igiugig to south of Dillingham. These showers are moving
slowly westward towards the coast and near coastal waters of
Bristol Bay as they weaken and dissipate.

&&

.MODEL DISCUSSION...

Guidance continues to be in good overall agreement considering
synoptic features. There continues to be some minor discrepancies
with regards to a where a triple point low will form along the
Bering Sea front Sunday evening. Most guidance has this subsequent
low forming just west of the Pribilof Islands. However, the 00z
ECMWF does not fully form a triple point low, and the main Bering
low remains dominant. The main forecast challenges during the
short-term will be fine-tuning corridors of heavier precipitation
throughout the central Aleutian Chain, southwest Alaska, and
eventually coastal Southcentral Alaska. Precipitation-type could
also present a challenge for Tuesday morning when the front
arrives to mainland Southwest. It is possible to have a brief
period of snow at the onset of precipitation, especially in
portions of Bristol Bay. The 00z NAM is the coldest of the
guidance with this idea.

&&

.AVIATION...

VFR and light winds will persist through the morning hours. The
pressure gradient will orient east-to-west along the north Gulf
Coast along with a slight up-inlet gradient to allow
southeasterly Turnagain Arm winds to bend over the terminal this
afternoon. These winds will become light and variable overnight
into tomorrow morning. There could be a few light showers this
afternoon as weak upper-level shortwaves lift northwestward over
the area in association with an upper-level low in the western
Gulf near Kodiak Island. However, VFR conditions are still
anticipated.

&&

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

A shortwave trough will push a weak front across the northern Gulf
towards coastal areas today. This will produce light rain from
the Kenai Peninsula towards Prince William Sound. As the shortwave
lifts north this afternoon, a few showers are possible from
Anchorage to the Mat-Su valley. Cooler air is expected to move
across Southcentral as the front moves onshore tonight lowering
snow levels between 500 and 1,000 feet. However, most of the
precipitation will be along the coast with sea level locations
seeing rain. On Monday, an occluded front will move into the Gulf
and Kodiak Island with stronger winds up to Gale Force and areas
of moderate to heavy rain along coastal locations. Winds will
increase Monday and continue through Tuesday across Turnagain Arm,
the Knik winds across the Matanuska valley, and across the Copper
River valley. This front will move north as we head into Tuesday
with moderate to heavy precipitation spreading across the eastern
Kenai Peninsula and Prince William Sound. Snow levels will be
between 500 to 1,000 feet Monday night and Tuesday morning while
increasing to 1,500 to 2,000 feet Tuesday afternoon. This will
allow for some light snow accumulations across Turnagain Pass.

&&

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

A broad low pressure system will continue moving eastward across
the Bering Sea and Aleutian Islands today through Wednesday. This
low will produce gale force winds across the central and eastern
Bering at times. Cold off shore flow will persist across Southwest
Alaska as this low is expected to take an offshore track. Hence,
temperatures will remain cool and increase the chances of snow
mixing in with rain on Tuesday across the Kuskokwim Delta and
Bristol Bay.

&&

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

At the start of the period, the main feature to note is a low
pressure system in the Gulf pushing westward toward the eastern
Aleutians/Alaska Peninsula (AKPEN). This will lead to a broad
area of rainfall along with northerly gap winds for the region and
coastal areas of Southcentral Alaska. As the aforementioned low
pushes southward, a couple of weaker systems will settle into the
Gulf of Alaska, bringing unsettled conditions lasting for much of
next week. With the exception of high elevation showers, a strong
upper ridge extending northwestward from Canada will support
drier conditions and near normal temperatures for the southern
mainland. Out west, a strong low approaching the Kamchatka
Peninsula will push its front toward the western Bering Sea,
bringing rain and gusty winds into the Aleutian Chain by early
Friday.

&&

SYNOPSIS AND MODEL DISCUSSION...DAN
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
LONG TERM...MF