Gale Warning 546, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
512 PM AKDT Tue Oct 6 2020

.ANALYSIS AND UPPER LEVELS...
In the upper levels there is a longwave trough over the Alcan
border and extending south-southwest into the North Pacific to
around 40N. The upper level ridge is over the eastern Bering sea
and leaving a tight gradient between it and the upper level low
near just east of the Kamchatka Peninsula.

This northwest Bering Sea region is where the next strong low can
be seen on satellite with a front extending through the central
Bering Sea. This will be the low of significance for much of the
upcoming week for the forecast area. A much weaker low which will
not be of much consequence is in the northwest Gulf of Alaska and
should dissipate overnight.

&&

.MODEL DISCUSSION...
Models are in good agreement though Thursday night when the
triple-point low develops along the front near Kodiak Island.
While the models still hold together in the Bering Sea, the Gulf
of Alaska remains unsettled with model solutions. Mashing all the
model information together to see what information we can glee,
it looks likely that a triple-point low will develop in the
southeastern Gulf on Friday and head northwestward as the main
low by Friday. However, there is still a large spread in
solutions as to how far the low moves and how strong it will be.

&&

.AVIATION...
PANC...VFR conditions will persist. Winds will turn to the
Southeast around midnight but should remain in the 8-12 kt range.
These winds will also remove any chance for fog in the morning.

&&

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

Quiet conditions are expected across much of Southcentral through
Wednesday morning. A series of upper level shortwaves will lead to
potential showers near higher terrain. The strongest of these
will move west to east over the region late tonight through early
Wednesday morning. A front will track over Kodiak Island Wednesday
afternoon and move eastward through Thursday, leading to moderate
rainfall along the coast. However, total amounts will be much
lower than last week's system. The front will likewise lead to
gusty winds developing along Turnagain Arm and the Anchorage
Hillside persisting through early Friday morning. As such, areas
in the lee side of the Chugach Mountains are expected to remain
mostly free of precipitation. Model agreement degrades through
Friday, however the overall showery pattern along the coast looks
to continue with drier conditions inland.

&&

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

An occluded front (warm occlusion) will approach Southwest Alaska
this evening resulting in an increase in southeasterly winds
across the area. The front will be weakening as it continues to
move eastward. Precipitation will begin across the Kuskokwim
Delta late this evening and will reach the Kuskokwim Valley early
Wednesday morning. Precipitation type will mainly be rain across
the area. There is a chance of a few flakes mixed in at the onset,
however it will quickly change to rain as the southerly flow will
keep temperatures too warm for snow or mixed precipitation.
Higher elevations in the Ahklun and Kilbuck Mountains will
experience snow. The front will then weaken into a residual trough
over the Kuskokwim Valley and result in showers continuing on
Thursday and Friday while temperatures gradually warm across the
area.

&&

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

A strong front in the central Bering will weaken as it moves
eastward. The front will move inland Wednesday morning. The low
that is associated with this front will move into the north
central Bering Sea on Wednesday. A widespread area of gale force
west-northwesterly winds will persist across the western
Bering/Aleutians on Wednesday and Thursday, these winds will then
gradually ease on Friday. Large 20-25ft seas are expected in the
western Bering/Aleutians on Wednesday and Thursday due to the
large fetch from the west-northwesterly winds, these seas will
remain long in period. Seas will then gradually abate on Friday.

&&

.MARINE (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska:

Gales associated with a barrier jet are possible
along the North Gulf Coast from Montague Island west. There is
significant disagreement on the track and strength of a low
tracking along the front causing the barrier jet. If the low is
strong, gales could be more widespread over much of the Gulf on
Saturday. Following a middle ground weaker low, gales may be
possible over the offshore waters and along the North Gulf Coast.

Bering Sea:

A low over the central Bering may cause gales along the Western
and Central Aleutians Friday. Behind the low, gales may develop
over the far western Bering on Saturday. No gales are expected
elsewhere.

&&

.LONG TERM FORECAST (Days 3 through 7: Friday through Tuesday)...

For much of mainland Southern Alaska, the long term looks like a
quiet period. On Friday rain activity associated with a dying
front could bring some light rain to portions of Bristol Bay. A
front over the northern Gulf will cause rain and gusty winds along
the north Gulf Coast into Sunday. The caveat with that is if and
how strong a Gulf low that may move into and then circulate around
the Gulf into Sunday becomes. There is a lot of disagreement on
that. If the low remains far enough from the coast then the rain
potential along the coast will be reduced. Elsewhere, high
pressure over the interior and a storm track largely south of the
area will keep offshore flow ongoing for much of Southwest Alaska
and portions of Southcentral, which should allow the dry weather
to continue.

Temperature-wise, a seasonable slow cooling is expected.
Depending on the track and strength of the Gulf low, warmer air
may stick around through the weekend. The cooler temperatures are
more likely for Monday and Tuesday. Since it will be a gradual
cooling and not sudden, this too will favor continued quiet
conditions.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Surf Advisory 155.
MARINE...Storms 174 176.
         Gales 150 155 165 170-173 175 177-181 185 411-414.
FIRE WEATHER...NONE.

&&

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