Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 220032
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
432 PM AKDT Fri Apr 21 2017
.ANALYSIS AND UPPER LEVELS...
A ridge of high pressure over Western North America is channeling
moisture from the subtropics into the Northern Gulf of Alaska. A
low in the southern Gulf of Alaska is responsible for pulling the
slug of wet air northward. The wetter air has encountered a
resistant drier atmosphere near land slowing the onset of rain,
even to Kodiak Island. By midday, only showers had reached outer
Prince William Sound and Kodiak Island. Forecast challenges for
Southcentral Alaska will continue to be timing and extent of
precipitation, especially for those around the Kenai Peninsula and
western Prince William Sound.
Over the western Aleutians, a Pacific low will creep eastward
keeping the Bering Sea in a broad, cold, easterly flow through the
weekend. Forecast challenges for Southwest Alaska and the
Aleutians will be related to local wind effects and waves of
precipitation around the Pacific low.
Models are in general agreement at initialization and through most
of the short term period. The NAM has a slightly faster solution
for moving the Pacific Low across the the North Pacific this
weekend. Both GFS and NAM agree that the focus for lift and
orographic influences will be over Kodiak Island and Southwest,
so the focus for precipitation this weekend will follow those
A NAM-GFS blend was used over Southcentral. The GFS was selected
for Southwest Alaska and the Aleutians.
PANC...VFR conditions are expected for the ensuing 24 hr period.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
High pressure will remain over Southcentral Alaska through the
short term, but will slowly track north. This will allow some room
for a front approaching the Gulf to move into the central Gulf and
bring rain to Kodiak Island beginning this evening. The front will
then stall over the Gulf but it looks to bring a chance of
showers to southern and eastern parts of the Kenai Peninsula.
Winds should stay light under the effects of the high pressure but
some weak diurnal winds may occur.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A pattern change will bring warmer and windier conditions to the
mainland. The upper low pressure off the coast is moving into the
northern Bering, allowing a new front and disturbance to slide
into the eastern Bering. Widespread clouds will move over the
mainland beginning late tonight, accompanied by a chance for
sprinkles and light rain near the coast. Easterly and
northeasterly winds will be gusty, especially during daytime
hours. The front/disturbance responsible will be stretching and
weakening for the next couple days, any precipitation over the
mainland will be very light. Low-level winds coming over the
terrain will warm, driving daytime high temperatures into the 50`s
in many areas, while keeping nighttime low temperatures elevated
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Easterly winds and light rain/snow will dominate the forecast for
the next couple days. A front and low pressure system south of the
western Aleutians will set up shop, drawing a system from the Gulf
of Alaska over the Bering. Both fronts will be weakening with no
gales expected after tonight. Otherwise expect a chance of light
rain/snow in most areas and moderate easterly winds.
.LONG TERM FORECAST (Days 3 through 7)...
Next week continues to look like a generally cloudier weather
pattern across most of the mainland, with shower activity both
along the coast and also at many inland locations. This will be a
change from the past many days of widespread sunny weather, but
will still be seasonable mild and pleasant in most areas. A large
but weakening and generally benign low pressure system currently
moving into the central Aleutians will slowly make its way to
Southwest Alaska. Winds should remain relatively light throughout
the state as the overall pressure gradient will be minimal.
MARINE...Gales 131 132 138 150 173-175 178 351-152.
SYNOPSIS AND MODEL DISCUSSION...DS/EN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML