Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 230027
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
427 PM AKDT Fri Jun 22 2018

.ANALYSIS AND UPPER LEVELS...
An upper level low over the Bering Sea and a weaker trough over
the Gulf of Alaska continue to bring cloudy and cool weather to
much of the state today. As the upper level trough slowly moves
through the Southcentral region, the radar reflects a slowly
shifting precip boundary along the Kenai Peninsula. Over the
western mainland, radar is showing a series of showers training
over Bethel that is associated with a trough from the low in the
Bering Sea. These showers are heavier in nature and are reducing
visibilities but haven`t had much other impact. Meanwhile, a
shortwave ridge in the far western Aleutians is leading to broad
areas of fog across the western Bering Sea.

&&

.MODEL DISCUSSION...
Models are in good agreement on the larger features in the next 48
hours. Due to the overall level of instability, actual locations
of showers are difficult to resolve between the different model
runs. Moving into the Sunday/Monday timeframe, upper levels are in
pretty good agreement about an easterly wave moving into the
Copper River Basin, but how this plays out later on at the surface
has some differences between the model runs. If the NAM plays out,
this easterly wave will remain further to the east, with fewer
impacts over the Southcentral area.

&&

.AVIATION...
PANC...Some MVFR conditions are expected this afternoon, but
these lingering lower clouds should break up by evening. VFR
conditions and light winds are then expected through Saturday
evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Weak cyclonic flow aloft combined with weak instability will allow
a few light showers to linger across Southcentral through this
evening, though do expect a drying trend. After this, instead of a
weak upper level ridge building in, it now looks like Southcentral
will remain under the influence of cyclonic flow, with all
computer models now indicating a distinct short-wave trough
moving from the eastern Gulf tonight to the Copper River Basin on
Saturday. Based on this, have trended wetter across the Copper
River Basin. Weak flow and instability elsewhere should keep the
remainder of the area mostly dry, with just a few showers focused
along the mountains. The short-wave will also reinforce cloud
cover across the region, but do think areas farthest away should
see at least some breaks of sun during the day Saturday. This
includes the Kenai Peninsula on up to Anchorage and perhaps even
portions of the Mat-Su.

The upper level will flatten out and linger over interior
Southcentral Saturday night through Sunday. Storm motion will
advect showers westward from the Copper River Basin to the Mat-Su.
A few showers may make it as far south as Anchorage and the Kenai
Peninsula. Sunday definitely looks like the cloudier day of the
weekend. A second upper wave will approach the Copper Basin from
the east on Sunday. Low level warming just ahead of it looks like
enough to destabilize the atmosphere and produce a few
thunderstorms.

The flow becomes more chaotic on Monday and it`s hard to hone in
on any specific feature to focus showers. For now, have used a
very broad brush approach to the precipitation forecast.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
A fairly stagnant pattern is setting up across the mainland. The
bands of showers across the Kuskokwim Delta and Greater Bristol
Bay will wane this evening. At the same time any shower activity
will stay confined to the mountains, possibly some drifting off
toward Naknek overnight. The next two afternoons will look much
the same. Overall, decreasing cloud cover with breaks of sun in
the afternoon will lead to late afternoon shower activity, mainly
along higher terrain. The next front will approach from the
Bering Sea early next week, but will be weakening as it does.
Expect temperatures slightly above normal, and light winds for the
period.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
A weak front with rain showers will fall apart over the central
Bering Sea this afternoon and evening. The next front, sub-gale-
force, will pivot from west to east across the chain beginning
late tonight. Rain will spread across most of the area through the
weekend, shifting to the Alaska Peninsula early next week.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The long term forecast begins Monday night with the Sunday night
with the main feature the low in the eastern Bering Sea near the
Pribilof Islands. The deterministic models, ensemble runs, and WPC
are in agreement with this low position and intensity through the
week. The models, ensemble and WPC remain in good agreement with
the resolution of the ridge in the Gulf of Alaska being squeezed
and pushed to the east as a frontal low from the Bering Sea low
pushes into the Gulf late Wednesday. As we move out into the
latter part of next week the main low moves over the mainland as a
ridge builds in behind it over the Bering Sea.

This all translates to a continuation of the cool, cloudy, and
wet pattern over the southern mainland. As the frontal low pushes
into the Gulf Wednesday, more rain and clouds can be expected
along the Gulf coast to Kodiak Island.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...LF
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...SA


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