Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 201256
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
456 AM AKDT Thu Jul 20 2017

.ANALYSIS AND UPPER LEVELS...
Rain continues along the North Gulf Coast this morning but has
begun to slowly diminish from north to south across the remainder
of Southcentral and the Bristol Bay region as a large upper level
low crosses the Alaska Peninsula into the Gulf. An associated
front is beginning to pivot from northwest-southeast to more of an
east-west orientation and sink to the south with the advance of
the low, keeping widespread rain over the Gulf waters and Kodiak
Island. High pressure and marine stratus are in place across much
of the Bering, although a North Pacific disturbance undercutting
the ridge is bringing rain to portions of the Western and Central
Aleutians as it tracks quickly to the east-southeast.

&&

.MODEL DISCUSSION...
Models show good synoptic agreement into the weekend as the upper
low continues into the far southern Gulf and the Bering ridge
begins to extend eastward across the southern mainland, signaling
a shift to a warmer and drier pattern in the coming days. Given
the overall model consensus, preferred the enhanced detail of the
NAM for the morning forecast package.

&&

.AVIATION...
PANC...Winds will increase out of the southeast this afternoon in
response to surface heating in the southern Susitna Valley and a
weakening down-inlet pressure gradient. Winds will then subside by
late evening. VFR conditions are expected through the TAF period.

&&

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

The front that has been bringing widespread rain to Southcentral
over the past several days will slowly weaken today and drift
south into the Gulf of Alaska. Radar this morning already
indicates a downward trend in precipitation intensity and
coverage. Meanwhile, the cross barrier coastal jet continues to
maintain its strength and support downsloping as well as gusty
winds in Prince William Sound and the Barren Islands region.
Conditions will continue to improve Friday as an upper level
ridge pushes further into the region and supports clearing skies
and warmer temperatures. A few diurnal showers could form by
afternoon along the Alaska Range and Talkeetna Mountains, but
generally rainfall will be limited. In addition, winds will be
much weaker across Prince William Sound, Cook Inlet and the Barren
Islands as pressure gradients slacken Thursday night into Friday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
As the low south of the Alaska Peninsula continues its track to
the south, ridging will build in over southwest Alaska. In
between these two features there will be enough instability over a
corridor from the Middle Kuskokwim Valley through the Ahklun
Mountains for potential thunderstorm development. After the
ridging moves in, shower activity will be diminished through
Saturday with only some light afternoon showers, mainly over the
mountains.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
Ridging continues to build in over the Bering from the west
bringing fog to many areas around the Bering and Aleutians. A low
that is traveling south of the high is moving through the Western
Aleutians and is headed for the Central Aleutians before tracking
south into the North Pacific. High pressure will then dominate the
Bering until a warm front moves into the western Bering Saturday,
then tracks through the northern Bering.

&&

.LONG TERM FORECAST (Days 3 through 7)...

At the start of the long term forecast on Sunday a low amplitude
upper level ridge over the southern Bering keeps the Aleutians and
southern mainland in a dry regime. A strong shortwave racing
east from Kamchatka Sunday night increases chances for rain
showers into Monday along the northern and eastern Bering as the
wave rides along the periphery of the ridge. This strong wave is
expected to dive southeast over the Kuskokwim coast, allowing
multiple weak waves to follow. This energy develops into a new
upper level trough over the gulf by the middle of next week.
Overall, the southern mainland continues in a dry pattern through
the next week with increasing chances for afternoon showers
mainly along the mountains.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CB
AVIATION...CB
SOUTHCENTRAL ALASKA...ELN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...KH


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