Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 220030
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 PM AKDT SAT MAY 21 2016
.ANALYSIS AND UPPER LEVELS...
A cold core upper level low sits relatively stationary over the
Northern Bering with ridging to the east over the far eastern
Gulf, Panhandle, and northwestern Canada. Water vapor satellite
indicates an upper- level disturbance with weakening front is
located from the central Alaska Range south into the central
Gulf,and is continuing to shear apart. A second disturbance is
moving northeast across the Aleutian Range and up Cook Inlet
toward Anchorage. A more robust disturbance with associated
surface front is located from the southeastern Bering through the
eastern half of the Aleutian Chain. Meanwhile, high pressure
ridging aloft persists over the Kamchatka region.
The models are in good synoptic agreement into the mid-term. The
disturbance moving into Southcentral will continue to move through
the area tonight, and will be followed by a weak, subtle upper
level ridge late tonight into the first half of Sunday. The
synoptic scale upper low over the northern Bering begins moving
east tonight and continues across southern Alaska through
tomorrow night, resulting in a pattern change toward an active
zonal for the early to middle part of the coming week.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Wet conditions will generally remain in the forecast through
Monday for Southcentral Alaska as a front moves through the region
tonight and a second shortwave is expected to move into the area on
Sunday night. Currently conditions are clearing over Kodiak Island
and portions of the Kenai Peninsula in the wake of the front with
a weak shortwave ridge transiting the area. As the ridge moves
through overnight, there is the chance for some partial clearing
and patchy fog to develop over the Western Kenai Peninsula
northward through the Anchorage Bowl and into the Palmer/Wasilla
area in the morning. Winds over much of the mainland will decrease
through the period, with the exception of Southern Cook Inlet,
Kodiak Island, and through the Barren Islands where breezy west to
south winds are expected in the wake of the low.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
Showery conditions across the Southwest Mainland will continue to
taper off through early this evening. A brief reprieve in
rainfall will be seen across Southwest Alaska through this
evening...before another wave of rain moves into the Southwest
coast overnight tonight. This quick moving front will track
through the Southwest Mainland Sunday, bringing widespread rain to
the area and gusty conditions along the coast and Alaska Peninsula
through Monday morning. Another brief reprieve will be seen early
Monday morning, before another weak shortwave traversing the zonal
upper level flow over the Bering quickly brings another shot of
rain back to the Southwest Mainland and Alaska Peninsula through
Monday Afternoon. Temperature will remain on the cool side and
quite possibly below normal through Monday, as a cold core upper
level low remains just to the west of the southwest mainland.
During the breaks in rainfall, patchy to areas of fog will be
possible with fairly light winds and well saturated surface layer.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
A fairly unsettled weather pattern will continue across the
Bering Sea through Monday, with a longwave trough encompassing
much of the Bering Sea. Within this trough lies several potent
upper level lows and shortwaves which will continue to move
through the Bering Sea, bringing rain to much of the region. The
low currently over the Eastern Bering is expected to quickly push
northeast toward the Southwest Coast tonight, bringing Rain and
small craft to minimum gale winds and seas to the eastern
Aleutians and Bering through early Sunday morning. The pattern
begins to break down on Monday as the upper level flow becomes
more zonal and allows weak surface high pressure to build across
the Southern Bering Sea. Expect fog to form along the eastern
Bering Sea during the morning hours today with the thicker fog
likely limited to northern portions of the Bering. By Sunday,
areas of fog will begin to develop over Bristol Bay and extreme
Eastern portions of the Bering Sea, which will mix out during the
afternoon hours and re-develop with the loss of daytime heating
and stabilization of the surface layer.
.LONG TERM FORECAST (Days 3 through 7)...
By early next week as a shortwave departs the south mainland, the
models have trended towards a much warmer and drier pattern
next Wednesday for much of mainland Alaska. This will occur as
from the Eastern Bering Sea moves over the mainland, this will
however be relatively short lived as an arctic trough will dive
southward through the state late Thursday-Friday, bringing cooler
air and showers to the mainland through the work week.
The change in forecast confidence over the mainland is largely a
result in better agreement that an upper level trough over the
western Bering will stall out and remain mostly west of the
dateline. There is now good confidence that a gale force low will
move northward through the western Bering/Aleutians next Tuesday,
bringing rain and gusty south winds to the area into Wednesday
SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP