Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 260012
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
412 PM AKDT Mon Sep 25 2017

.ANALYSIS AND UPPER LEVELS...
A stacked and weakening upper low is located over Bristol Bay
with an elongated trough extending east across the Southwest
Mainland to across Southcentral/Alaska Range. At the surface the
associated low is drifting south across Bristol Bay with its
frontal trough extending from the Kuskokwim Delta to along the
Alaska Range. Light rain was evident along the frontal boundary
with a few showers across Bristol Bay and Southcentral. Satellite
imagery shows a broad cloud band, associated with a developing
surface low and frontal trough, streaming north from the NE
Pacific to over the Gulf. High pressure continues its hold over
the western/central Bering Sea and Aleutians.

&&

.MODEL DISCUSSION...
Models still differ with the handling of the low complex over the
southwestern Gulf. The GFS seems to have been the more consistent
of the solutions over the past day or so. So will continue in that
direction on this forecast issuance.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
There are pockets of lingering rain showers on the latest radar
image from the Kenai and the Middleton Island radars. Generally
expecting mild weather this evening and most of tomorrow for the
Anchorage Metro area. The longwave pattern features a closed low
over the AK Peninsula aloft and at the surface, the low is
reflected over the western Gulf Of Alaska southwest of Kodiak.
This new system will bring gales and precipitation to Kodiak and
much of the Gulf of Alaska. Late Tuesday and into Wednesday expect
moisture to advect northeastward into Prince William Sound and
portions of Southcentral AK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A drying trend is underway across the southwest mainland as the
low near the Alaska Peninsula weakens and moves away from the
area. These conditions will persist through early Wednesday as
offshore flow increases ahead of the next North Pacific low
moving up towards Kodiak Island. Fog will remain possible tonight
across portions of the Kuskokwim Delta and Lower Kuskokwim Valley
as clearing skies promote enhanced radiational cooling processes,
however fog potential should still diminish over time through
Wednesday morning as the offshore gradient increases. The
possibility of rain will return to areas along the Akpen and
Aleutian Range by late Wednesday as the front associated with the
approaching low moves into the region.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The combination of the dissipating low north of Cold Bay and the
next system approaching Kodiak Island will keep the bulk of the
shower activity focused on the southeast Bering from Dutch Harbor
to the Akpen through midweek. Gale force winds will develop over
the coastal waters south of the Akpen by Tuesday as the next front
arrives, with Small Craft Advisory conditions farther north into
Bristol Bay. The western half of the Bering will remain in a much
more benign pattern in north to northwest flow as high pressure
builds slowly eastward through Wednesday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Day 3 (Thursday) will start off with a sfc ridge centered over
Shemya that extends across the vast majority of the Bering Sea and
an area of low pressure over Kodiak Island. This low pressure
system will bring decent rainfall to the gulf coast and Kodiak
Island before it weakens on Friday and begins to drift eastward.
The sfc ridge over the Bering will quickly retreat into the North
Pacific over the weekend as a pattern shift begins to take hold
across Alaska and Alaskan waters. The pattern change comes in the
form of the upper level pattern shifting from a more subtropical
(meridional) influence to a more arctic (zonal) influence. This
will keep the subtropical jet well south of Alaska while the
arctic jet begins to strengthen as cold air begins to build up
over Russia. It`s that time of the year where the cold air over
Russia helps low pressure systems develop/strengthen over
Kamchatka and Siberia and the models are hinting at the potential
for several robust system to push off the Russian coast and into
the Bering Sea next weekend and through the first half of next
week. It`s way too soon to give any details on any potential
system next week but the pattern change is on the way.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning 120 131 132 138 150.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...PS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...MC


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