Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion...corrected
National Weather Service Anchorage Alaska
457 am akst Friday Nov 28 2014
Analysis and upper levels...
mainly clear skies prevail across southcentral Alaska this morning
beneath an upper level ridge...with the exception of a few
persistent areas of low stratus and fog from the Anchorage bowl
and Matanuska Valley into the Copper River basin as moisture
remains trapped beneath a low level inversion. A few middle and high
level clouds are beginning to work their way into the Cook Inlet
region and Susitna Valley as the ridge axis shifts gradually
eastward. A weakening front is spreading a mix of rain and snow
showers over portions of Bristol Bay and the lower Kuskokwim
valley as it pushes inland from the eastern Bering Sea. Strong
winds have generally subsided across the Bering as a low pressure
system tracks northward towards the Bering Strait...but widespread
showers remain over the region beneath cyclonic flow aloft.
forecast confidence remains above average in the short term as
models show good agreement with respect to synoptic features
through the weekend. Preferred the GFS over the western part of
the domain and continued to utilize higher resolution models
closer to the Gulf for their handling of small scale features.
Short term forecast southcentral Alaska (days 1 and 2)...
With the upper level ridge moving to the east there are some
clouds moving into southcentral from west to east today. Most of
the area will remain without precipitation today except for Kodiak
which will be in the rain. The increasing cloudiness will help to
reduce the fog in the Cook Inlet region today but a strong
inversion to around 1300 feet...as seen on the Anchorage radiosonde observation this
morning...will keep some areas of fog and stratus around through
the morning. The Copper River basin remains entrenched in the
stratus and may have a difficult time breaking out today. The
increasing middle and high level clouds may help to bring some more
mixing through the atmosphere and improve conditions this
A strong short wave will move through southcentral Alaska Saturday
and this is what will bring in the snowfall late tonight into
Saturday afternoon. This trough will move through the area rather
quickly as another upper level ridge moves into the area late
Saturday night into Sunday. This will limit the snowfall to just a
few inches for most locations across southcentral.
Short term forecast southwest Alaska (days 1 and 2)...
surface ridging across the southwest Mainland breaks down today
as a combination of weak troughing works inland from the Kuskokwim
Delta and another surface low moves a front up from the North
Pacific. Isolated to scattered snow showers will become numerous
in the afternoon across the Kuskokwim and Bristol Bay. A warmer
air mass along and south of King Salmon will support
precipitation to fall as rain...with snow mixed at times.
Precipitation will diminish on Saturday from west to east as
ridging builds back into the southwest from the Bering.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
low pressure over the northern Bering pushes a shortwave over the
eastern Bering today. Precipitation develops along this wave as rain
with snow mixed north of the Pribilof Islands. The next
significant front moves into the western Aleutians by Saturday
morning bringing heavy rain and gusty gale winds. The low center
driving the front moves across the central Aleutians late Saturday
pushing the frontal boundary through much of the Bering by
Long term forecast (days 3 through 7)...
By Sunday an upper ridge will build over the eastern Bering while
a trough with embedded cut-off low digs into the western Bering.
As the ridge moves to the alcan by Tuesday the cut-off will cross the
Bering and then the akpen into the North Pacific on Wednesday. An upper
low from northern Canada will rotate around the remains of the
ridge and arrive near the Bering Strait early on Thursday. At the
surface...a low moving across the Aleutians will be forced to
pinwheel in the western Bering on Monday before recrossing the
Aleutians near Dutch Harbor late on Tuesday and then moving into the
North Pacific on Wednesday. A low will move into the northern Bering on
Thursday. A warm front associated with the original Bering low will
cross southwest Alaska on sun and then southcentral Sunday night
through Monday. The trailing cold front will sweep across the
Aleutians sun and Monday. Finally the occluded front will affect
southwest Alaska and southcentral Tuesday and Wednesday.
Forecast confidence is fairly high sun through Tuesday...and then
becomes less so as models begin to diverge with positions of the
lows both in the northern Bering and south of the akpen. Wpc was
used as a good average position of features through Thursday. This
solution brings wind and rain to the Bering and Aleutians on the
eastern flank of the low through at least Tuesday...with wind...and
rain changing to snow showers on the western flank through Thursday.
Southwest and southcentral will have rain and snow Sun night
through Wednesday...with rain on the coast and snow showers inland on
Marine...173 174 175 176 177 178.
Synopsis and model discussion...cumulonimbus
southwest Alaska/Bering Sea/Aleutians...kh