Scientific Forecaster Discussion
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Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
153 PM akdt Wednesday Apr 23 2014
Analysis and upper levels...the upper level high that has been
over the state has begun to push northwestward as an upper level
low has moved into the northern Gulf of Alaska. This is producing
easterly flow over southwest and southcentral Alaska today. There
are a couple of easterly waves...upper level disturbances moving
from east to west...that are embedded in this flow. These waves
have caused some of the increased cloud cover and rain showers.
The jet stream is running just south of the Aleutian Islands and
is providing the source for a strengthening low south of the
western Aleutians. This will cause the low there to rapidly
strengthen and absorb the weakening low in the central Bering Sea
tomorrow as that low does not have any upper level support.
Model discussion...models are in good synoptic agreement through
the remainder of the week. One item they all seem to be catching
up on is the speed at which the first easterly wave that moved
through southcentral Alaska traveled this morning. This wave has
crossed the Alaska Range this afternoon and is moving faster than
anticipated by previous model runs. The second easterly wave is
over northern Prince William Sound early this afternoon and headed
to the west. The models may have tried to mix these waves into one
previously as neither is very strong.
The models do diverge a bit staring early next week but there
still looks to be a general pattern emerging that we can work
Short term forecast...
southcentral Alaska...the atmosphere is somewhat unstable this
afternoon with rain showers being produced as the easterly waves
move through the area. The precipitation has not been as
widespread as radar indicates however as the lower atmosphere
remains fairly dry causing a good amount of the showers to
evaporate into virga.
A front in the southwest Gulf of Alaska is pumping a bit of
moisture into the southern half Kodiak Island. The northern
portion including the city of Kodiak is out of the main push of
moisture but will see some showers as well. There is a chance they
become more widespread over the island this evening as the latest
satellite loops indicate a low that developed along this front is
edging to the northwest.
Southwest Alaska...there is some increasing clouds in conjunction
with an easterly wave in the upper Kuskokwim valley and another
region of clouds south of King Salmon. In between there are some
showers developing over elevated terrain as the daytime heating
provides low level lift.
Bering Sea/Aleutians...the low in the central Bering Sea is
weakening but is still impacting the weather there. The
eastern Bering Sea has some clouds near the low and along a
dissipating front but also has a large area of sunny skies as
well. Rain showers persist in the western Aleutians in the
northwest flow there.
Long term forecast...
the low that moves into the southwestern Gulf Friday night will
remain nearly stationary and slowly weaken through the weekend.
There is some uncertainty added to the forecast after this low
dissipates as the models are struggling to come to a common
solution as to what happens next. At this time the most likely
scenario involves the low track to move into the Bering Sea with
some semblance of high pressure over southern and southwest
Alaska...which builds northward into the eastern interior part of
the state by the middle of next week.
marine...Gale Warning 150 155 165 170 172 173 174 176