Area Forecast Discussion
Issued by NWS Anchorage, AK

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573
FXAK68 PAFC 171651 AAA
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion...UPDATED
National Weather Service Anchorage AK
851 AM AKDT Tue Sep 17 2019

.ANALYSIS AND UPPER LEVELS...

The active weather pattern continues for our forecast area. A
shortwave ridge is currently sliding east through the Gulf of
Alaska and there is troughing dipping south from Interior AK. This
troughing has actually sparked some showers in the early morning
hours in Southcentral AK, to include the Anchorage Bowl. The next
low in the pattern is in the Bering Sea and is tapping into deep
moisture from the subtropics as expected. Finally, another low can
already be seen on satellite and is located just southeast of the
Kamchatka Peninsula. This quick succession of systems will
continue rainy weather for our forecast area.

&&

.MODEL DISCUSSION...

Forecast confidence remains high with good agreement in the
models. Some timing adjustment was needed for an incoming low
pressure system on day 3 in the Gulf of Alaska, but this change
was not enough to decrease confidence. Models continue to handle
the active weather pattern well.

&&

.AVIATION...
PANC...VFR conditions will persist. Winds will start the TAF
period light and variable, but will increase tonight with
Turnagain Arm winds. Wind shear will also be possible with the
increasing winds speeds.

&&

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

An upper level wave is moving through Southcentral early this
morning and bringing some rain to the Copper River Basin and some
showers as far south as the Anchorage Bowl. These showers should
dissipate during the morning as the disturbance moves to the
east.

The main weather event is the front that will move into the region
from the southwest tonight through Wednesday (sooner for Kodiak).
While there will be some gusty winds through channeled terrain,
the moisture is very deep and the flow aloft will remain
southwest. Therefore downsloping will be limited and the entire
region should see rainfall. Many locations will see over an inch
of rain tonight through Wednesday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3; Today
through Thursday)...

Rain will track west to east through today along a warm front.
The heaviest rain is expected to occur in the afternoon and
evening. Widespread accumulations over one inch are likely with
localized higher amounts. Rain will taper to showers by Wednesday
and continue through the day under an upper level trough.
Precipitation will become more scattered overnight into Thursday
as the associated low departs to the north, thereby diminishing
southerly winds.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3; Today
through Thursday)...

Showers and gusty westerly winds will continue through Wednesday
morning across the Aleutians and Pribilofs south of a low.
Another low will track into the western Aleutians by Wednesday
evening bringing rain and gusty northerly winds. It will quickly
move south, though some lingering scattered showers may continue
across the Aleutians into Thursday.

&&

.MARINE (Days 3 through 5)...

Beginning the extended period marine forecast on Thursday, there
will be a low moving northeast from the North pacific into the
Gulf of Alaska. This low will reach the North Gulf by early
morning Friday, likely bringing gale force winds to much of the
North Coast as the warm front/barrier jet increases in strength.
The low will then occlude and remain in the Gulf of Alaska through
Saturday with winds becoming westerly/offshore as the low moves
east toward the ALCAN. Yet another strong low moves into the Gulf
of Alaska on Sunday and Monday as the storm track remains directed
over the Gulf with much more quiescent weather over the Bering
Sea through the weekend.

&&

.LONG TERM FORECAST (Days 3 through 7)...
There is good agreement amongst the models of an unstable pattern
remaining over southern Alaska through the weekend. This would
keep a chance of showers for most locations. However, the
Aleutians and north Gulf coast will see more activity with a
series of lows tracking through the area from west to east while
staying just south of the Aleutians.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 150 155 170 172-178 181 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BJB
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AP
MARINE/LONG TERM...KO



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