Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
134 PM akdt Sat Aug 30 2014
Analysis and upper levels...
there is a deep upper low over the Arctic Ocean centered to the
north of the northwest coast. Strong flow aloft associated
with this low is pushing systems from Siberia toward Alaska. The
flow is weaker further to the south...with a few weak short-wave
troughs. One of these is along the Alaska/Canada border. Another
is just entering the Gulf of Alaska from the Alaska Peninsula and
a third is over the south central Bering Sea.
the numerical models are in good agreement through 60 hours...then
in fairly good agreement through the next 24 hours. There are some
minor differences on timing and strength of various upper level
systems...but these are only minor and forecast confidence is a
bit higher than normal today.
Short term forecast...
For south central Alaska...the weather will remain basically dry
through Tuesday with westerly flow aloft. There are a couple of
exceptions to this. Over the eastern Copper River basin and from
about Cordova eastward...the weak system along the Canadian border
will continue to produce showers. This system will get a little
extra push of moisture on Sunday...but will finally push east on
Monday. The second exception is associated with a system currently
in Siberia...but with the fast westerly flow will push into
central Alaska by Monday afternoon. This system will bring a
chance of precipitation to the Susitna Valley (and maybe even the
Matanuska valley) and northwest portions of the Copper River
basin later Monday into Tuesday.
For southwest Alaska...dry conditions will continue into Sunday
with weak ridging over the area. A weak upper level system may
bring some rain to the Kuskokwim Delta and lower Kuskokwim valley
later Sunday. A stronger system moving into central Alaska on
Monday will bring a good chance of rain to most of the
area...spreading east and south through the day Monday. Lingering
showers are expected Monday night and Tuesday as westerly flow
For the Bering Sea/Aleutians...the system near the Panhandle and
the one over the southern Bering Sea will both push southeastward
and weaken/dissipate tonight into Monday. Strong high pressure
will build over the southern Bering Sea Monday and remain through
Tuesday. The (low pressure) system sliding by to the north later
tonight into Monday will strengthen the surface gradient over the
central and northern Bering Sea...and then weaken again as the
system moves eastward.
Long term forecast (sep 3rd - Sep 6th)...
an upper level low centered over the Beaufort Sea will bring
southwest to westerly winds to the Bering Sea and southwest Alaska
from midweek heading into next weekend. This will generally bring
more cloudy and cooler conditions with scattered showers for
southwest Alaska. The southcentral Mainland and the northern Gulf
will start off under the influence of an upper level ridge. This
will bring drier conditions by midweek as the ridge continues to
propagate to the east through weekend. There will be westerly
winds by midweek and shift to south to southwesterly by Thursday.
These winds will continue into next weekend resulting in an
increase in clouds and the chance for precipitation.
Ludwig/pld Aug 14