Area Forecast Discussion
Issued by NWS Anchorage, AK

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374
FXAK68 PAFC 020041
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
441 PM AKDT FRI JUL 1 2016

.ANALYSIS AND UPPER LEVELS...
The upper level low remains over the Gulf of Alaska, but is
beginning to show signs of moving east. The strong short-wave
system on the northwest side of the low that provided last nights
rainfall to south central Alaska is now in southwest Alaska. There
is an upper level low over the southwest Bering Sea as well as the
western and central Aleutians. This low has stalled and is
continuing to weaken. A weather front associated with this low
stretches from about Nikolski northwestward across the Bering
Sea. A ridge of high pressure separates these two low, with the
"col" over the far eastern Bering.

&&

.MODEL DISCUSSION...
The numerical models are in reasonable agreement on the over-all
pattern. There continue to be some differences in the timing,
location, and strength of various short-waves surrounding the
Gulf low. There are also some minor differences in the handling
of precipitation, especially in regards to convection. Therefore
the forecast confidence is slightly below normal.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Sat and Sun)...
Afternoon mountain showers and diurnal sea breezes will be the
story for the weekend. The easterly wave that brought a third to
an inch and half of rain across Southcentral has cleared through
most of the area. The Alaska Range has slowed its westward
progress keeping some rain falling over Kachemak Bay. It will
pivot through this corridor on Sat bringing rain to parts of
Kodiak Island later tonight through the Sat morning hours.
Meanwhile...the rest of the area will remain in very light flow
with generally moist and unstable conditions. With all the recent
rainfall...many places could see some patchy fog or low stratus
develop overnight. But this should dissipate relatively quickly on
Saturday as some sun breaks through. Showers should develop along
the mountains in the afternoon, but with weak steering flow, we
don`t expect many of them to make it into valleys. The best
instability remains farther north over the Alaska Range and parts
of the Talkeetna Mountains, so can`t rule out an isolated
thunderstorm developing on those higher peaks. Sun looks very
similar to Sat with minimal change to the pattern. The leftover
band of rain near Kodiak should move off into the Gulf making for
drying conditions there.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The Gulf low that has been relatively stationary the last couple
of days will finally push off to the east tonight. This will
change the easterly flow over the area to be more northerly which
will help to diminish showers over the area. The majority of the
rain remaining by the beginning of next week will be in the more
eastern parts of Southwest Alaska like the Alaska and Aleutian
Ranges.

Even though the main upper level low is departing there are still
more shortwaves moving through the area with the strongest one
coming through this evening. It will track south from the
Kuskokwim Valley towards Bristol Bay and will help to initiate
thunderstorms in the area. There will also be enough instability
over the Kuskokwim Valley for possible afternoon thunderstorms
Saturday and Sunday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The broad area of low pressure over the Western Aleutians will
track slowly east over the weekend. It looks to bring light rain
to the Aleutians with some making it to the Pribilof Islands on
Saturday. By the beginning of next week the broad upper level low
will be absorbed into a broad trough extending across the Bering
from the north. This trough will keep light rain over the Bering
and Aleutians.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The upper level pattern will begin to shift by the end of this
weekend to a more stable pattern, as the upper low shifts further
east and weak high pressure aloft builds in from the west. Thus,
with everything being weak, any precipitation that develops Sunday
over southern mainland Alaska will be mostly scattered and weak.
The persistence of a mid-level unstable layer over much of the
area will result in some diurnal showers mainly along the
mountains.

For the Independence Day holiday, a strong upper level trough will
dig southward across the eastern Bering. Ridging will build east
of it across the Gulf. However, the models are in disagreement
with how quickly the ridge builds, and where the trough axis sets
up over the Bering. Currently, the models agree enough for the
4th of July to suggest a return to southwesterly winds in the
upper levels. Since the disturbances depicted in the models all
remain weak, the weather looks similar to Sunday at this point for
much of mainland Alaska.

Active weather should persist for much of southern Alaska into
midweek as the trough over the Bering moves into mainland Alaska.
However, the model differences and associated forecast
uncertainty only compound with time concerning how quickly and in
what form (open trough or cutoff low), the troughing moves east.

&&


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

&&

$$

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



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