Small Craft Advisory 83, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
506 PM AKST Thu Jan 23 2020

.ANALYSIS AND UPPER LEVELS...

The upper level pattern with a trough over the mainland part of
the state and ridge over the Bering persists. The surface low
track remains south of the Aleutians out west. In the GUlf a low
can be seen near Middleton Island as the cold advection off the
Aleutian range gets wrapped up in it and keeps it nearly
stationary. That cold advection can be seen best of visible
satellite out of the gaps and channeled terrain from Resurrection
Bay southwestward to the Alaska Peninsula.

&&

.MODEL DISCUSSION...

Models remain in good agreement into Saturday around the region
and the Bering Sea area remains under good agreement into next
week. The issue in in the Gulf of Alaska by Saturday night when a
complex low starts to give the models fits as to how it will
develop and where the main low centers in it will be.

&&

.AVIATION...
PANC...VFR conditions and light (mostly) north winds are expected
to persist into Friday.

&&

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

Colder temperatures are expected to settle across the region
tonight as cold air advects from the interior to the Gulf of
Alaska. Gusty conditions develop through channeled terrain this
evening with gusts already established across the western gulf.
The strongest gusts are expected through typical areas such as Seward,
Thompson Pass, Whittier, Matanuska Valley, Broad Pass and Copper
River Delta. Mostly dry conditions are expected for inland
location and the western Gulf, with isolated to scattered snow
showers across the northeastern Gulf. The next front to monitor
develops across the eastern Gulf late Saturday, taking a slow
northwest track through Sunday. Increased snow chances along the
northeast Gulf coast on Sunday as models all show the boundary
pushing to Cordova in the morning. .

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Tonight
through Sunday)...
A blocking ridge over the eastern Bering Sea will lead to cold,
windy, and dry conditions across Southwest Alaska over the next
few days. Northerly flow will continue to advect clouds across the
Kuskokwim Valley and Kuskokwim Delta tonight, but expect at least
partial clearing by Friday as colder and drier air advects
southward from the Arctic. The magnitude of cold air advection
across Southwest Alaska will be weak through Friday night, though
both the ridge to the west and a low in the Gulf of Alaska will
strengthen with time, leading to tighter pressure gradients and
stronger winds. The presence of clouds and wind will initially
limit temperature drops, but generally expect a steady downward
trend in temperatures over the next couple days. For those areas
exposed to the winds, this will also lead to falling wind chill
temperatures. Have made some adjustments to existing wind chill
advisories for the Kuskokwim Delta and Bristol Bay to delay the
onset of the coldest wind chills (-40 degrees or colder). Further
adjustments will likely be needed as we fine-tune the temperature
and wind forecasts.

The strongest winds will be along the south side of the Alaska
Peninsula, as cold air funnels through the bays and mountain
passes. As we head through the weekend the a digging trough over
the Gulf will push the Bering ridge westward and the low level
flow will shift to a north to northeast direction. A reinforcing
shot of cold air advection will cross Southwest Alaska Saturday
night through Sunday and head toward the southern Alaska Peninsula.
This change in flow will shift the strongest winds south and
westward along the Alaska Peninsula. The persistent winds and cold
air advection of the next few days will also lead to widespread
areas of Heavy Freezing Spray across the Southwest Alaska coastal
waters. With the significant surge of cold air over open waters of
the eastern Bering Sea on Sunday, would also expect development
of snow showers.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through
3/Tonight through Sunday)...
A compact, but potent low south of the western Aleutians will
become vertically stacked tonight, slowing the westward
progression of the low. It will then weaken as it continues to
the far western Bering Sea Friday through Friday night. Meanwhile,
an occluded front strung out along the western to central
Aleutians will lift slowly northward tonight, then stall on
Friday. A core of storm force winds ahead of the front will shift
from the western to central Aleutians northward into the Bering
Sea offshore zones tonight, then gradually diminish through
Saturday. Expect periods of rain and snow, with surface
temperatures along the Aleutians remaining largely above freezing.
Another Pacific low will approach the Aleutians Saturday night
through Sunday, leading to restrengthening of winds. The
prevailing wind will remain easterly over the next three days
across the western half of the Bering Sea and along the Aleutian
chain.

&&

.MARINE (Days 3 through 5: Saturday through Monday)...

Gulf of Alaska:

An occluded low and a surface low will persist over the Gulf of
Alaska Saturday, Sunday and Monday bringing moisture to the region.
Strong high pressure over the mainland coupled with the low
pressure in the Gulf will produce strong offshore flow winds,
especially near the Barren Islands and Kamishak Bay. Gale force
winds and heavy freezing spray possible.

Bering Sea and Aleutians:

A strong low south of the western Aleutians will keep widespread
gales with the possibility of isolated storms across the central
and western Bering Saturday and Sunday. Freezing spray will
continue to impact portions of the Bering. Winds will decrease by
Monday.

&&

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

Looking at the synoptic pattern, expect low pressure over the
Gulf of Alaska and south of the Aleutians with a dense cold
airmass building up over the mainland. Below normal temperatures
will continue for western Alaska and southcentral Alaska. This
setup will result in enhanced gap winds through the coastal
mountains with precipitation mainly along the coastal regions of
the Gulf.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind chill advisory 155 161.
MARINE...Gale 119-121 127 129-132 138 150 155 170 172-174 178 185
		 Storm 175 176 177
 Heavy Freezing Spray 126 127 129 130 132 138 139 141 150-165 179
180 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BB
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SEB
MARINE/LONG TERM...PJS