Scientific Forecaster Discussion
Northern Alaska forecast discussion...corrected
National Weather Service Fairbanks Alaska
1247 PM akst Friday Dec 26 2014
Corrected typo in paragraph 4 of surface discussion
a very active weather scenario is expected over the northern
Alaska forecast area during the next few days.
current operational runs of the GFS/NAM/ECMWF are in generally
good agreement out through Sun afternoon...GFS/ECMWF reasonably
similar thereafter out through Tuesday. A cold upper trough over the
west and northwest coasts of Alaska will weaken slightly as it
moves eastward to the alcan border by midday Sat.
Upper level ridge currently extends from eastern Siberia to
the Alaska Peninsula. The ridge will build and increase in
amplitude as it moves eastward to the alcan border and
southward by Sun afternoon.
A weak low amplitude short wave trough will move northward
across the Bering Sea Friday night...and move across the
chukotsk peninsula Sat.
A stronger short wave trough will move rapidly northward
across the west and northwest coasts sun into sun evening...
gradually intensifying as it move northward and developing
into a closed upper low over the western Beaufort Sea by late Sun
night. This upper low will then curve northeastward then eastward
through the upper ridge which will be squashed down some...ridge
axis being pushed eastward into the Yukon territory by late Sun
night. As this low exits off to the east... another ridge will
move northward...extending from St Matthew island to the
northwest Panhandle and southward by midday Monday. This ridge will
move northeast...axis extending from wrangel island to the
Panhandle by Tuesday afternoon. For Tuesday night and Wednesday...ridge
weakening and moving into the Yukon territory as several short
waves punch northeastward across the northern Alaska Mainland.
Another ridge likely rebuilding over central and western Alaska
Wednesday night into Thursday and Thursday after the short waves dampen out as
they exit northern Alaska.
periods of stormy weather expected for the West Coast as
multiple surface systems and their associated fronts
move northward across the West Coast. Strong southwest winds
expected over to develop over northwest Alaska late Sun night
as the second system in the series intensifies as it curves
northeastward then eastward across the Arctic Ocean.
958 mb low centered near 55n/170e move in a wobbly trajectory to
near 58n/168e by Sun afternoon...filling to 980-985 mb. Sun
afternoon position based on a mean between the GFS/NAM positions.
Its associated front will move northward across St Lawrence
Island early Sat morning...then weakening some during the day Sat
as it proceeds northward, easterly gales developing over St
Lawrence Island this evening...snow with blizzard conditions
possible after midnight as the frontal snow band moves north. Zone
214 may see a period of snow and blowing snow with reduced
visibility as the front approaches and moves through. Snow ending
or tapering to snow showers with diminishing winds over St
Lawrence Island by early Sat morning after the frontal passage.
Some snow will be possible over Norton Sound and the southern
Seward Peninsula with this system.
The next system is likely to be more intense...GFS deepening
the system more rapidly than the NAM/European model (ecmwf) as it moves northward
up the West Coast...all three models deepening the system it
moves northeastward then eastward across the Beaufort Sea and
Arctic Ocean...with the GFS being most energetic. NAM is
moving the system somewhat faster than the GFS. Will lean
towards the GFS run for this forecast cycle. Am expecting a
990-995 mb low center to move northward to near St Lawrence Island
around midday sun...deepening to a 985-990 mb center near 73n/165w
by late Sun night. The low is prognosticated to move rapidly northeast
then east to near 75n/123w by Monday evening filling to 990-995 mb.
Brisk southeast winds developing on the northwest coast sun
evening increasing to southwest gale later Sun night. Southwest
gales developing over the western Arctic coast and central
Beaufort Sea coast and offshore areas late Sun night... southwest
to westerly gales spreading to the eastern marine zones and the
central and eastern Arctic coast by Monday afternoon. Low visibility
with blowing snow likely on the Arctic coast with these strong
winds...with local blizzard conditions possible. Winter storm
watches will likely be needed for the Arctic coast...but it is a
bit too early for issuance on this forecast cycle.
Another period of strong winds and precipitation likely
to begin over St Lawrence Island and the West Coast from
St Lawrence Island southward by Monday evening....GFS/ECMWF
taking a moderately strong low northward to near the pribilofs by
Monday morning with a secondary system developing 200-300 miles to
With these three systems...temperatures will likely be warm
enough for mixed precipitation at times over zones 212-214-215
and possibly in zone 211. Freezing rain may be possible at
Over the interior...snow or snow showers likely over most of the
central/eastern interior tonight and Sat with the upper trough
moving east...some snow or flurries may linger in the northeast
interior Sat night.
Strong southerly Chinook winds expected to develop in
Alaska Range passes sun...likely continuing into Monday
night. Wind advisories will probably be need to be
issued for the Alaska Range on the next forecast cycle.
Coastal hazard potential days 3 and 4...none
Winter Weather Advisory for akz218-akz221-akz222.
Winter Storm Warning for akz213.
Winter Weather Advisory for akz214.
Heavy freezing spray warning for pkz210.
Small Craft Advisory for pkz210.
Gale Warning for pkz210.
Brisk Wind Advisory for pkz200-pkz215-pkz220-pkz225-pkz230.
Rf Dec 14