Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 261230
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 AM AKDT Fri May 26 2017

.ANALYSIS AND UPPER LEVELS...
A broad upper level trough remains over the majority of the AOR,
with some ridging building over the far western Bering, and
another ridge ahead of the trough over the pacific Northwest. The
trough remains evident on IR satellite imagery, with the clearing
line transiting further east over the Yakutat area. A few
lingering showers continue to tapper off over some of the
mountains along the northern Gulf coast, Alaska range, and
Talkeetna mountains. Further west, a surface low just south of
Cold Bay continues to bring some rain and gusty winds to the
Alaska Peninsula.

&&

.MODEL DISCUSSION...
Overall model guidance seems to be in good synoptic agreement
with each other. Larger differences start to occur as we move
into the weekend, and watch the evolution of a strong wave moving
out of the Bering. American models seems to be charging the way
with regards to this feature, both faster and deeper than the
Canadian and European solutions. By Sunday afternoon, model spread
increases both at the upper and lower levels of the atmosphere,
decreasing overall confidence as we go into the holiday weekend
and into next week.

&&

.AVIATION...
PANC...Gusty southerly winds will continue through this afternoon
and evening. Some showers are possible again this afternoon and
evening as well, but VFR conditions should prevail.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
Clouds and showers will be on the increase yet again today as a
weak short- wave moves up from the Gulf. However, the flow will be
different than yesterday, with southerly flow this morning
backing toward the southeast in the afternoon. The areas most
likely to see showers will be from Western Prince William Sound
across the Kenai Peninsula to the Western Susitna Valley, with
isolated to scattered showers across the remainder of the region.
Also, upper level temperatures will gradually warm so the
atmosphere will not be as unstable as Friday, though still
unstable enough to produce some locally heavy rainfall.

Attention will then shift to a low pressure system south of the
Alaska Peninsula. An upper level short-wave dropping southeastward
across the eastern bering Sea today will re-invigorate this low as
it continues south of the Alaska Peninsula tonight, amplifying the
flow. This will spread rain northward from Kodiak Island to the
north Gulf coast tonight through Saturday. Flow will shift solidly
to southeast leading to downslope drying in the lee of the Kenai
and Chugach Mountains. Thus, the bulk of rain will be confined to
the coast along with upslope areas along the west side of Cook
Inlet and the Susitna Valley. Even if it stays dry inland clouds
will fairly extensive, so temperatures will remain on the cool
side.

Looking to Sunday, the upper trough will evolve into a closed low
and lift northward into Southwest Alaska. Depending on the exact
track (and direction of flow over Southcentral), there is
potential for rain to spread inland.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Southwest Alaska will remain in a generally troughy pattern for
the next several days bringing a continuation of the present cool
showery weather pattern. While the trough that moved through
yesterday is now clear of the area allowing showers to weaken
somewhat and become less frequent, a surface low south of the
Alaska Peninsula and tracking east will spread additional moisture
north into Southwest Alaska. Showers will reintensify and
increase in coverage this afternoon and evening as solar heating
aids instability. A trough associated with the surface low will
rotate across Bristol Bay this evening and extend north into
Southwest Alaska where it will remain stalled tonight through
Saturday. The surface low will begin drifting slowly north
Saturday night to move into Southwest Alaska on Sunday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The surface low currently south of the western tip of the Alaska
Peninsula will continue east then stall over the southwestern
Gulf. A flat ridge bringing low stratus and patchy fog will
progress from the western Aleutians/Bering east to the central
Aleutian/Bering tonight and to the eastern Aleutians amplifying
northwest across the Pribilof Islands Saturday and Saturday Night.
The next frontal system will reach the western Aleutians late and
continue east to the central Aleutians Saturday night where it
will stall through Sunday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The extended forecast begins on Monday with the cut off low that
is poised to develop near Kodiak Island this weekend lifting
northward through western Alaska. This will occur as part of an
amplification of the large scale pattern over the course of the
next week, with a sprawling longwave trough encompassing the
Bering Sea and western mainland as a stout ridge builds over
western Canada. Forecast confidence remains lower than normal as
models continue to diverge on the smaller scale details, but this
synoptic pattern will generally result in continued cloudy and
showery conditions across the southern mainland as broad onshore
flow remains focused along the gulf coast between the large scale
features. Benign showery conditions can also be expected over much
of the Bering beneath the upper trough. Temperatures will
gradually climb back to around normal through the week as the cut
off low departs into the arctic at the beginning of the week and
scours out what remains of the colder air aloft.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...TP
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...CB



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