Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
142 PM akdt Monday Sep 1 2014
Analysis and upper levels...the large cold upper level low just
off the Arctic coast remains in place today as the next trough
extends out from it and into western Alaska. The ridge over south
central Alaska is being displaced eastward by this trough and
therefore more clouds are moving into the region. The surface
ridge over the Alaska Peninsula and Aleutian Islands is holding
firm today which is bringing zonal westerly flow across the Bering
Sea and into southwest Alaska.
models are in good synoptic agreement for the next few days. The
biggest area of concern begins Tuesday night south of the Alaska
Peninsula where a North Pacific low is elongating and possibly
forming a triple point low. The way this system develops is
handled much differently especially between the European model (ecmwf) and the
GFS. The GFS appears to move the low farther north way too fast
resulting in it placing the low about 500 miles northeast of the
European model (ecmwf) solution. The overall dynamics support the more southerly
Route and slower timing closer to the European model (ecmwf) model. However there
is a good chance that the two models will converge on a solution
that may be between the two...but closer to the European model (ecmwf).
Short term forecast...
southcentral Alaska...the ridge that has brought a number of sunny
days to south central Alaska is moving eastward as the next upper
level disturbance emanating from the Arctic low moves toward the
area. The bulk of the energy with this trough is north of the
Alaska Range so most of the precipitation associated with it will
be from Talkeetna northward. The rest of south central will
likely just see increased clouds.
as with south central the majority of the energy with this trough
is north of the area which is limiting the heaviest precipitation
to the Kuskokwim valley. The zonal westerly flow is bringing a
large amount of stratus into southwest Alaska which is already on
shore in the Kuskokwim Delta area and will move into the Bristol
Bay region this evening. There may be some light rain and drizzle
as well as fog associated with this.
the majority of the Bering Sea is under the marine stratus however
the ridge over the Aleutians and Alaska Peninsula is strong enough
to bring mostly sunny skies from Adak eastward. The stratus will
eventually make in back into the Alaska Peninsula overnight and
the rest of the Aleutians sometime Tuesday.
Long term forecast...
the southcentral Mainland and southwest Alaska will be under the
influence of a low pressure system moving through the Bristol Bay
region by Friday. This system will move inland over the weekend
bringing widespread moisture and rain with gusty winds. The
central and western Bering Sea will have stratus and fog as high
pressure builds into the area heading into next weekend. A North
Pacific low will approach the central Aleutians by Saturday
afternoon before tracking into the central Bering Sea by Monday.
This system will bring abundant moisture and precipitation with
gusty northeasterly winds.