Small Craft Advisory 362, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
320 AM AKDT Sun Apr 26 2020

.ANALYSIS AND UPPER LEVELS...

Clear skies allow for dry conditions across mainland Alaska this
morning that set up another beautiful day today as much of the
active weather has moved out of the region. Water vapor imagery
shows a low spinning and continuing to move south of Kodiak
Island, which is keeping some cloud cover in this region. The
western Aleutians are Bering are seeing a bit more action as a
vertically stacked low continues to move eastward towards Shemya,
allowing for a showery pattern to persist this morning.

&&

.MODEL DISCUSSION...

Models continue to be in good agreement overall with the synoptic
pattern. The GFS is still keeping precipitation a bit farther
north and west on Monday for the Cordova region. The past few GFS
runs have been trending more in line with other models, thus
allowing for a blend of models to be used in the forecast package.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

Sunny and dry conditions are expected for the next couple of days
over most of Southcentral as high pressure remains over the area.
Some clouds are expected to the east of Prince William Sound at
times due to a strong low in the northeast Gulf. A stray shower in
that area is even possible, but fairly unlikely through Monday
night. The low in the northeast Gulf will bring fairly strong
winds to the northern Gulf, possibly approaching gale force in the
offshore waters.

&&

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

Mostly clear skies will persist in a weak, northeasterly flow.
Ample sunshine will keep temperatures above average, though they
will be much cooler along the Kuskokwim Delta coast.

&&

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

Scattered showers will continue generally west of Unalaska through
Monday afternoon until a ridge builds over the area. A front will
track across the far western Aleutians Monday afternoon into
Tuesday bringing moderate rain and gusty southerly winds. More
benign conditions are expected for the central and eastern
Aleutians until Tuesday morning. After this, the previously
mentioned front will move into the central Aleutians for the
remainder of the forecast period.

&&

.MARINE (Days 3 through 5)...

Bering Sea/Aleutians:
The next feature of interest to impact the Bering is a front
associated with a Kamchatka low pressure system. Southeasterly
gale-force winds, with potential areas of storms look to impact
the western Aleutians/Bering Sea early Tuesday morning.
Waves/swell will not come up in earnest until early Wednesday
morning with combined seas approaching 10 ft, building to 14 ft by
Thursday. The front will weaken as it pushes eastward into the
central Bering, with some areas of low-end gales. Early Wednesday
morning, a second push of gales with embedded storms will impact
the western Chain as southwesterly winds wrap around the south end
of the low pressure system. After Wednesday morning, that system
will decay and return benign conditions to the Bering Sea with
small craft conditions around that system with light and variable
winds for the eastern Bering Sea.

Gulf of Alaska:
A broad area of low pressure will sit over the Gulf during this
time,  while low pressure centers develop and rotate around the
low. The first will come in from the east on Tuesday morning along
with a max small craft front. The second will be a much weaker
system that decays in to a broad area of weak low pressure with
benign conditions.

&&

.LONG TERM FORECAST (Days 3 through 7)...

Unsettled weather is expected throughout the Bering Sea and
Aleutian Islands throughout the forecast period while models have
trended towards calm and dry conditions over Mainland Alaska.
Frontal precipitation and cold air advection is expected to impact
the Central and Western Aleutians through Saturday morning as the
system slowly occludes. High pressure over the Interior and
offshore flow should prevent precipitation and high winds from
reaching the western coastal areas. Overall the GFS and EC remain
consistent with yesterday's 12Z runs with the next frontal system
forecast to reach the Western Aleutians Saturday night and into
Sunday morning. Small discrepancies do exist in strength of the
low coming off of the Kamchatka Peninsula with the GFS favoring a
stronger system.

Model solutions over the interior and Southcentral differ greatly
from yesterday. Both the EC and GFS have developed a closed,
blocking high over Central Alaska through the forecast period.
This feature should prevent the surge of cold, dry air situated
over the Canadian maritime from reaching Southcentral Alaska,
which the models had indicated yesterday. This feature could still
provide forecasting challenges Thursday and Friday as the models
do indicate a positive vorticity advection max, albeit weaker,
traversing the Alaska Range through Saturday morning. Weather
within the Gulf of Alaska is forecast to remain active through
Sunday with multiple North Pacific lows forecast to move into the
Gulf area. The first weak frontal system could impact the
Southcentral Coast Thursday afternoon. Precipitation type
forecasting should be safely all rain as 850 mb temperatures trend
closer to May climatology. A stronger low and frontal system will
begin to impact the southern Gulf of Alaska Saturday night and
into Sunday afternoon.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ALH
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CK
MARINE/LONG TERM...ML/CJ