Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 131215
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
415 AM AKDT Sat Oct 13 2018

.ANALYSIS AND UPPER LEVELS...
The upper level pattern features a semi-stationary low over the
eastern Bering with ridging over the eastern Gulf. Multiple
shortwaves are moving through the flow between these two features
with the strongest one spinning up a low in the Gulf that is
tracking towards the north Gulf coast. This setup is also bringing
enough moisture for rain across much of the southern mainland
with the heaviest along the north Gulf coast. Further west,
another low has moved south of the western Aleutians with its
front pushing into the central Aleutians.

&&

.MODEL DISCUSSION...
The models are in excellent agreement with the main synoptic
features including the low that will track just south of Aleutians
until Sunday night when it moves into the eastern Bering.
Yesterday the models were struggling with the timing of this low
but the 00Z runs seem to have locked in on a solution.

&&

.AVIATION...
PANC...Stratus over the area is expected to lift throughout the
morning, but there is some uncertainty with the timing. However,
after the trough that has been bringing rain to areas west of
Anchorage pushes through early this afternoon there is high
confidence it will clear out any remaining low clouds. Early
Sunday morning there will be another chance for stratus and fog to
develop but confidence is low in exact timing.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A low pressure system in the northern Gulf that is moving rapidly
northward will push inland around noon today. This system will
bring brief Storm force winds to the northern Gulf this morning in
the barrier jet. Breezy conditions are also expected in Turnagain
Arm, the Knik valley, and the Copper River basin. Rain over most
of Southcentral will taper off in the afternoon and evening hours
as the low moves inland and weakens. Winds will also diminish.
Ridging will briefly build over the area tonight and Sunday for a
period of fairly dry and benign weather. Some fog is possible as
the skies clear, with plenty of low level moisture and weak winds.
Another front will move into the northern Gulf Sunday afternoon,
and, to the Gulf coast Sunday night, and then begin to push inland
early Monday morning. This front is oriented west-to-east, and
thus the winds for inland areas will not be very strong.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The general weather pattern will remain unsettled today with
showers continuing to rotate onshore in association with the upper
low to the southeast of Saint Matthew Island. A flat ridge will
rotate inland tonight, tapering showers off and bringing the
potential for some patchy valley fog. The ridging, however will
be rather short lived as the next front pushes east across the
Alaska Peninsula on Sunday bringing rain and south to
southeasterly gale force winds to that area while east to
southeasterly winds increase across mainland Southwest Alaska
Sunday afternoon through Sunday night. Precipitation will spread
onshore Sunday night then turn to showers through Monday as the
frontal system rotates further inland.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The vertically stacked low currently located off the southeast
tip of Saint Matthew Island will remain in that general location
through midday then gradually weaken as it lifts north this
afternoon through tonight. A rapidly strengthening low to the
south of the western Aleutians will track east today to be located
south of the central Aleutians by this evening, then become
vertically stacked and continue more slowly east through Sunday.
The low will then begin filling and curve to the northeast
rotating across the western tip of the Alaska Peninsula and into
the southeastern Bering on Monday as it gradually weakens.

&&

.LONG TERM FORECAST (Days 4 through 7: Monday Night through Friday)...

A sprawling low centered in the eastern Bering continues to be the
focus around which all of the active weather expected across
Southern Alaska originates. The low will remain nearly stationary
about midway between Cape Newenham and the Pribilofs until it
moves over the Kuskokwim Delta on Thursday. The track is well
agreed upon in the models. This pattern that includes moist,
southerly flow off the Pacific will favor cloudy and showery
weather across all of Southern Alaska through Thursday. The
onshore flow will also keep the Turnagain Arm winds nearly
continuous for several days, though is unlikely to be particularly
strong at any one time. A front that will have a tropical
moisture feed is expected to produce heavy rainfall along the Gulf
Coast from Prince William Sound eastward through Tuesday. Upslope
winds behind the front will keep rain falling in this area
through Thursday.

From Thursday afternoon through Friday, both the GFS and EC models
show a strong low tracking north out of the Pacific into the
southwestern Gulf. After that, the models quickly begin to
disagree on the track of the low, so future forecasts should be
monitored as there is potential for this to be a high-impact
event.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Advisory...125.
MARINE...Gales...125 155 160 165 170 171 172 173 174 175 176 177
 178 180 413 414.
 Storms...119.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...JW


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