Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 290033
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
433 PM AKDT SAT MAY 28 2016
.ANALYSIS AND UPPER LEVELS...
Dry conditions prevail across the southern mainland this
afternoon as high pressure remains the dominant weather pattern
with an upper ridge centered along the Seward Peninsula. Several
low pressure systems surround the ridge. To it`s southeast, low
pressure over British Columbia is moving a shortwave across the
eastern Gulf and Panhandle. To the west...a low centered south of
Dutch Harbor is stationary with a second low over Kamchatka moving
a strong shortwave across the Western Aleutians. At the surface,
the pattern over the southern Mainland is a weak trough between
ridging to the north and south. The Bering pattern is slightly
more active; however, the two surface features are filling with
one over the eastern Aleutians and the other just north of Shemya.
The next storm system to watch across the Bering is currently
organizing south of the Western Aleutians.
Models are generally in good agreement with the synoptic pattern
through Monday night. The main challenge across the southern
mainland into Monday is the timing of an easterly wave which
brings thunderstorm potential for the Copper River Basin on
Sunday. For the Bering and Aleutians, the main focus shifts to the
developing storm system in the North Pacific which quickly moves
to the Western Aleutians Chain early Sunday. The NAM was favored
for Southcentral and the Gulf with the use of the GFS and ECMWF
for the Southwest and Bering.
Elevated fire weather conditions are expected during peak heating
of the afternoons and evenings across the southern Mainland. The
greatest concern today is across the Susitna Valley where
temperatures are expected to climb into the mid 70s. A Red Flag
Warning was issued for warm and dry conditions combined with
stronger northerly flow which develops this afternoon as the
ridge to the north squeezes the pressure gradient as it shifts
southeast. Conditions will improve briefly overnight and then
return for much of Sunday. A warning is also being issued for the
Middle Kuskokwim Valley and inland areas of the Kuskokwim Delta,
as warmer and drier conditions spread westward on Sunday along
with stronger northerly flow.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The main story in today`s forecast will be the well above average
temperatures and dry conditions for parts of the Mainland. More
summer-type clouds will show up for most areas, especially over
the mountains. rain showers will begin to work into the eastern
Copper River Basin this evening and overnight spreading westward
through Sunday afternoon. Most of this activity will be concentrated
along the mountains but isolated showers can not be ruled out in
most areas. The only chance for thunderstorms will be in the
Copper River Basin tomorrow. Temperatures will remain above normal
with light winds through Monday.
As ridging aloft begins to slide off to the northwest tonight,
cooler air aloft filters into the area from the east. That cold
air will bring instability, especially over higher terrain, and
bring diurnal showers or even thunderstorms to the area.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The southwest Mainland will continue to warm under sunny skies
and lighter winds this evening as ridging persists overhead. Sunny
and warm weather will continue over Kuskokwim Valley/Delta on
Sunday as well, along with increasing northeasterly flow in
advance of a developing surface trough. To the east over the
Alaska Range, weak instability will bring showers and possibly
even a strike or two through Sunday evening. These showers will
then spread throughout the southwest Mainland on Monday as a
shortwave moves overhead. There remains some uncertainty with how
strong this feature will be, but there in reasonable confidence
that this wave will spread showers throughout the area on Monday,
possibly with a few thunderstorms. If the shortwave becomes as
strong as the NAM is indicating, this would increase the confidence
in thunderstorm development, especially over Bristol Bay and the
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The focus is beginning to shift to a Northwest Pacific low that
will increase to gale force as it moves into the western/central
Aleutians on Sunday. Model agreement is improving on the track of
this low...allowing gale force winds to be added to the forecast
for most of the central and eastern Aleutians into Monday.
.LONG TERM FORECAST (Tuesday through Saturday)...
The dominant high pressure center creating warm and dry conditions
across the Mainland will slowly retreat to the west through early
next week. This will allow increasingly cyclonic flow to enter the
Gulf of Alaska and southern Mainland during the week. At this
point it looks likely that the most active weather will stay far
enough out to sea in the Gulf that most of the area will continue
to see a fairly good amount of sunshine, though diurnal shower
(and maybe thunderstorm) activity will slowly increase throughout
the week. Meanwhile, the Bering Sea and Aleutian region will
remain generally under the influence of high pressure and strong
low-level inversions that keep fog and stratus a persistent problem.
This large-scale weather pattern is very typical for this time of
year, and as such temperatures and sensible weather should follow
suit and be fairly close to climatology for temperatures and
precipitation across the forecast area next week.
FIRE WEATHER...Red Flag Warning 145 153 155.
SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK