Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 260115
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 PM AKDT Sat Mar 25 2017
.ANALYSIS AND UPPER LEVELS...
At the surface the dominant high pressure remains over the
northern Bering Sea extending across interior Alaska. A strong low
and the associated gale force front extends along the Aleutians
to south of the Alaska Peninsula. An inverted trough extends from
the low over the panhandle to the North Gulf Coast. Aloft we
remain under the omega block as we have an upper low south of the
western Aleutians with the upper ridge extending from the north
Pacific across the western Alaska Peninsula into the Bering Sea
and the upper trough that extends from the Arctic low across the
mainland into the Gulf of Alaska.
The east flow along the North Gulf Coast is rotating showers
along the coast. Off shore flow and dry conditions persist across
south central Alaska to southwest Alaska. The stalled front along
the Aleutians is holding the gale force winds across the region
while keeping temperatures warm enough to keep the precipitation
liquid west of Unalaska.
The models remain in generally good agreement in the short term
but continue to struggle with the placement of the low and
westward extend of the precipitation Monday night and Tuesday. We
have high confidence that snow will spread across Prince William
Sound beginning Sunday night, however, the models have been
limiting the westward extent of the precip area each successive
run for the past couple of days, thus lowering our confidence in
snow on the Cook Inlet side of the Kenai Peninsula.
PANC...VFR conditions and light winds will persist.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The Southcentral Alaska region remains under the influence of
an upper level trough. This synoptic feature will gradually swing
through the region, and is reflected at the surface with a weak
low pressure system in the northern Gulf. Therefore, look for a
showery regime with precipitation mainly along the northern Gulf
coastal communities. By Monday the aforementioned low pressure
system will have dissipated, but a 993 mb low in the lower
southeastern Gulf will start to track to the northern Gulf. By
Monday evening, the models have this system tracking onshore near
Seward. This feature bring snow showers to the Eastern Kenai
Peninsula, and the Prince William Sound region. Look for the
Anchorage Bowl to have a chance for snowfall to spill- over the
Chugach Mountains into the Bowl.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Much of the same is in store for the Mainland for the next couple
days. The only real change in the overall pattern comes on Monday
morning when the Bering Sea blocking high retreats enough to allow
the upper trough back over the area, bringing some slightly colder
air with it. From a sensible weather perspective, not much will
change. Dry and clear conditions will continue with generally
light northerly winds. Expect some stronger winds and gusts during
the daylight hours. Temperatures will remain below normal,
especially at night as the clear sky promotes much cooler
temperatures, mainly in protected valleys.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A decaying frontal boundary will remain in place for the next two
days. Light rain can be expected from Shemya through Atka as
easterly winds begin to relax. A new low pressure system will
bring a gale-force front south of the central Aleutians Sunday
afternoon. Currently it doesn`t look like the front will spread
over the chain. Otherwise general moderate easterly to
northeasterly can be expected over the Bering Sea.
.LONG TERM FORECAST (Days 3 through 7)...
Little change to the longer range forecast for most of the region.
By the day three timeframe, guidance is still in agreement that a
surface low will spin into the Gulf as an upper level wave rides
south from the interior. Coastal locations will see precipitation,
but the question remains on the Anchorage area and how good of a
chance there will be for snow in the area. As each day passes
confidence increases and there is a decent chance that the
Anchorage will see some snowfall into Tuesday.
At this time, confidence remains too low to go any higher than a
chance of snow or to think about totals. The bottom line is that
the pattern is changing. The longwave pattern undergoes a bit of a
shift following this early week system and will set us up to be
in a little bit of a favorable patter to see systems beyond the
forecast timeframe reaching all of south central.
MARINE...Gale 155 172-175 178.
Heavy Freezing Spray 139 179 185.
SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL