Small Craft Advisory 245, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
359 PM AKDT Sat Mar 14 2020

.ANALYSIS AND UPPER LEVELS...

A 1051 mb high is over the Copper River Basin along with a surface
trough extending from southeast Alaska to the north Gulf Coast
while a 1045 mb high is over the Gulf of Alaska. The interior high
pressure coupled with the trough is fueling the outflow winds
through the Chugach Mountains. Out west we have a weak low in the
central Bering that is dissipating. Another low is well south of
the Alaska Peninsula and eastern Aleutians. Moisture from this
system is flowing north around the high pressure over mainland
Alaska, grazing the northern half of the Kuskokwim Delta. Weak high
pressure is over the western Bering Sea with a front extending
from a low over the Kamchatka Peninsula that extends through the
extreme western Aleutians.

&&

.MODEL DISCUSSION...

The forecast models remain in very good agreement into Wednesday,
thus forecast confidence remains high.

&&

.AVIATION...

PANC...MVFR to IFR conditions in fog is expected Sunday morning.
Light winds will prevail.

&&

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

High pressure remains over Southcentral Alaska today. The high
level cirrus clouds have been from the Alaska Range north, bringing
clearer skies today than the past two. A weak surface trough
remains along the northern Gulf of Alaska which is keeping the
gusty outflow winds blowing through Seward, Whittier, and the
Valdez area.
The clear skies have brought increased chance for some patchy fog
in the Cook Inlet area late tonight into Sunday morning. There is
a pretty good inversion over the area which increases the change
of fog. However, even if it does form, the strength of the sun
this time of year means the fog should burn off by noon.

The next system will bring some clouds into the region from
southwest to northeast on Monday.

&&

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

A strong Omega-Blocking pattern over the North Pacific will
continue to bring benign weather to most of Southwest Alaska this
evening through tomorrow afternoon as a 577Dm 500mb ridge
centered over the Gulf extends northward. The jet-stream is
currently bringing moisture to the western Kuskokwim Delta and
causing light snow across the area. Clouds will increase Sunday
evening with a chance of snow developing Sunday night as the
upper ridge shifts eastward. Snow is likely for Monday across the
Kuskokwim Delta as a warm front associated with the next low moves
in while 850mb temperatures remain below freezing.

&&

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

The jetstream is steering ample moisture across the central
Bering/Aleutians and Pribilof Islands. This will continue to
bring a steady rain through tomorrow across the central
Bering/Aleutians and Pribilof Islands. A strong southeast to
northeast oriented pressure gradient will continue to bring gusty
southeasterly winds this evening. As the pressure gradient slowly
weakens tomorrow and into Monday, winds will gradually ease.
Expect the highest winds in between gaps as well as downwind of
gaps on the Bering side of the Aleutian chain due to the
localized funneling of winds. Precipitation will gradually taper
off from west to east across the western and central
Bering/Aleutians Monday afternoon and evening as drier air in the
mid-levels advects from the west. A deep 979 mb low over the
northwestern Pacific Monday afternoon will bring large, long
period southwesterly swell into the western Bering. Swell heights
will approach 20ft in the western Bering Sea Monday afternoon
through Tuesday morning before beginning to gradually abate.

&&

.MARINE (Days 3 through 5 Tue through Thu)...

A front over the central Aleutians Tuesday morning will move
eastward and dissipate. As the remnants of this front enter the
Gulf, there is moderate confidence that a triple point low will
form near Kodiak Island, producing possible gale force winds
through the usual channels including Shelikof Strait, over the
Barren Islands, and through the gaps and passes of the Pacific
side of the Alaska Peninsula Tuesday through Wednesday.

There is high confidence a strong low will impact the Bering next
week. Beginning Tuesday morning, a gale force front over the
western Aleutians will push eastward across the Bering. Storm
force winds are possible. As the low center tracks northeastward,
there is potential for storm force winds on the backside of the
low Wednesday over the southwestern Bering. This low will track
northward and exit the Bering by Friday.

&&

.LONG TERM FORECAST (Days 4 through 7 Wed through Sat)...

Models continue to show good agreement with an upper level trough
over the southern Mainland drifting southward into the Gulf.
Upstream, an upper level ridge quickly moves through Wednesday
into Thursday, ahead of a large Bering low that pushes a strong
front eastward across the Bering. This front will likely impact
the Southwest coast midweek, bringing precipitation and strong
southerly flow. The track of this low still remains uncertain,
though models are showing the center departing the Bering to the
north by Friday. Overall, an unsettled weather pattern is expected
through next weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales 172 and 178.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...KO