Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
414 PM akst Friday Jan 30 2015
Analysis and upper levels...
An upper level ridge remains entrenched over the central Bering
Sea through southcentral and the interior of the state. This ridge
is also connecting with a ridge over the West Coast of North
America. An upper level low has cut off from the longwave trough
and is situated well south of the state.
At the surface high pressure is over most of Mainland Alaska
through the central Bering Sea with some weak low pressure in the
Gulf of Alaska. The main surface low is also well south of the
forecast area. This pattern is keeping a tight pressure gradient
along the north Gulf Coast through the eastern Aleutians and
including the southwest Alaska Mainland. This is a rather stable
pattern and will not change substantially through the weekend.
Short term model agreement continues to be good under the stable
pattern. Overall agreement between the GFS and European model (ecmwf) continues
into the middle of next week and then they diverge greatly. The
GFS has shown a more consistent solution from run to run but the
European model (ecmwf) has shifted the Arctic trough from the Bering Sea into the
Yukon in just a few runs. This amount of change puts a large
degree of uncertainty into the forecast for the second half of
next week as each of these solutions would have a huge impact on
temperatures and winds over the area.
Short term forecast southcentral Alaska (days 1 and 2)...
A long stretch of sunny and pleasant weather will Grace
southcentral well into next week as high pressure aloft builds in.
A deep low in the northern Pacific will track a front northward
into the Gulf of Alaska...tightening an already tight pressure
gradient along the coast. This will continue the general offshore
flow pattern...with local gap winds increasing through tomorrow.
Otherwise...beyond some very localized patchy fog and brisk wind
chills in mountain passes...no significant forecast concerns are
anticipated through Sunday.
Short term forecast southwest Alaska (days 1 and 2)...
Low pressure south of the akpen and high pressure over interior
Alaska will keep cold and dry conditions over SW Alaska into the
weekend...with some wind for the Kuskokwim Delta and areas north
of Dillingham. A slight warming trend can be expected sun and Monday
as warmer air moves inland from the Bering.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
Low pressure south of the akpen will bring a chance of rain and
snow to the akpen and eastern Aleutians through Monday. A low moving
past the western Bering will bring a chance of rain to the western
Aleutians during the same period. The rest of the Aleutians...the
Bering and the pribilofs will be dry with partly to mostly cloudy
skies into early next week.
Long term forecast (days 3 through 7)...
The beginning of next week starts off with a split flow pattern
with an upper ridge near the Bering straight and a low south of
the Alaska Peninsula. The ridge currently over the Mainland shifts
south Sunday night as a strong shortwave trough digs ahead of the
building ridge over the northern Bering. The southern Mainland
stays in a mostly dry pattern for the first half of the week as
subsidence occurs along the ridge. Rain and snow is largely
confined around the low south of the Alaska Peninsula through
much of the week.
The main challenges in the long range forecast are the temperatures
and precipitation next Wednesday through Friday. The ridge over
the southern Mainland begins to break down middle week as a strong
storm system pushes in from the northwest. There is a great amount
of uncertainty on how quickly the ridge breaks down...so kept a
drier trend intact throughout next week. After a brief warmer
trend at the beginning of the week...the southern Mainland returns
to colder than normal temperatures.
Marine...Gale Warning 127 131 132 138 150 155 172 178.
Heavy freezing spray warning 160.
Synopsis and model discussion...ez
southwest Alaska/Bering Sea/Aleutians...ds