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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
412 PM akst Thursday Nov 20 2014

Analysis and upper levels...
a broad but relatively low amplitude longwave trough is in place
over the Bering Sea and northern Pacific with persistent ridging
downstream over the West Coast of North America. A strong
160-180kt jet stream near 45n is flowing through the base of this
trough. A quick look at satellite imagery reveals one main storm
system...currently approaching the Alaska Peninsula from the
south...controlling weather across southern Alaska. This storm
intensified rapidly overnight with the help from the
aforementioned strong jet stream and bottomed out this morning
with a central pressure near 950 mb. An associated strong front
is impacting Kodiak Island and the southern Kenai Peninsula
coastline with storm-force winds and yet another round of heavy
rain. Strong winds are also blowing through the Aleutian Range and
into the Bristol Bay zone before wrapping around the low center in
the form of northwest winds over the eastern Aleutians and Alaska
Peninsula.

Further north...low-level winds remain sufficiently strong to keep
a classic downslope pattern in place across upper Cook Inlet. This
pattern should hold and possibly even intensify this evening as
southeasterly winds at mountaintop level gradually strengthen and
become more easterly.

Out west...cold air is beginning to once again filter southward
through the Bering Strait. Driven by northerly winds around the
low to the southeast...low-level convective processes are
leading to plenty of shower activity across the northwest Bering
Sea. Temperatures remain fairly warm at the surface...so precipitation
will continue to fall in the form of rain all along the Aleutians
as well as the Pribilof Islands.

&&

Model discussion...
the models are in very good agreement through the short term
forecast period. This is not terribly surprising given the very
slow expected progression of the major features during the
period. The high-resolution models (nam and Gem regional) are
favored today in order to take advantage of the Superior
depiction of strong winds throughout the complex terrain of
southern Alaska.

&&

Short term forecast southcentral Alaska (days 1 and 2)...
the front currently over Kodiak Island and the southwestern Gulf
of Alaska will move to the north Gulf Coast tonight and then
gradually weaken in place through Saturday. This will keep the
bulk of the precipitation confined to areas along the coast for
the next several days as strong cross barrier flow keeps inland
portions of southcentral Alaska mostly dry. Precipitation will mainly
be in the form of rain although snow may mix in at times at
higher elevations such as turnagain and Thompson passes...with
little to no accumulation expected. Gale force winds over the
Gulf and gusty southeast winds through Turnagain Arm and the
Portage Valley will gradually diminish through Friday morning as
the front begins to weaken.

&&

Short term forecast southwest Alaska and Bering Sea/Aleutians...
the North Pacific low will settle in over the Alaska Peninsula
tonight where it will remain through Saturday. The low is bringing
up warm air with it which will keep the eastern Aleutians...Alaska
Peninsula and Bristol Bay areas in rain through Saturday.
However...the Kuskokwim Delta and lower Kuskokwim valley will be
colder and could see some snow tonight. Additionally...with the
warmer air from the south overrunning the colder air in these two
locations there is a potential for some freezing rain to be mixed
in. But with the low overall precipitation expected there should
be little to no accumulation and the precipitation should diminish
overnight with none expected tomorrow. Out west northerly flow
will continue to bring rain showers to the central and western
Aleutians that will start to mix with snow tomorrow night as
colder air starts to move in from the north.

&&

Long term forecast (days 3 through 7)...

Models continue to be in great agreement through Monday...then
differences increase substantially by Wednesday. Models are all
generally showing a closed upper low over the western Bering Sea
moving eastward through the week...however the amount of
amplification of the pattern remains to be seen. A broad area of
low pressure over the Bering Sea during this period will gradually
move eastward...and will bring a series of fronts northward
toward the Gulf/Pacific coastal areas. Other than periods of
precipitation over the Aleutians/Bering Sea/Gulf Coast...it will
be difficult to pin down chances of precipitation for inland areas
until individual shortwaves within the flow are ironed out in the
coming days. Temperatures still look to gradually trend back
toward normal for this time of year...with no big cold snaps on
the horizon.

&&

Afc watches/warnings/advisories...
public...none.
Marine...none.
Fire weather...none.

&&

$$

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