Gale Warning 45, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
605 AM AKST Thu Mar 2 2017

.DISCUSSION...
The Mar 02/00Z 500 mb pattern continues to show broad troughing
over mainland Alaska with a 508 dm low now centered over the
central Gulf of Alaska. Strong 417 dm low/polar vortex remained
over the Canadian Archipelago. Between these two large features
short wave ridging was observed over the center part of the state,
with the east-west axis stretching from the Seward Peninsula to
the Yukon Flats. A ridge of high pressure at 557 dm was located
over the western Bering Sea, extending northwestward into eastern
Siberia. A few short waves were rounding around this ridge, one
moving through the central Chukchi Sea moving toward northwest
Alaska. A second one back in Siberia in the Shelikhova Gulf.

Surface: 02/06Z analysis shows broad low pressure stacked beneath
upper low in the Gulf with two embedded low centers; one located
around 160 miles southeast of Kodiak and another 994 mb low
located around 400 miles further southeast. Low pressure of 997 mb
was seen over the Canadian Archipelago, with troughing extending
southwest into the eastern Beaufort Sea with an arctic frontal
boundary extending west then northwest for the low center in the
eastern Beaufort Sea. Interior and western Alaska was under a col
between the two low pressure systems, with 1040 mb high pressure
centered in the Bering Sea and a 1036 mb high pressure centered in
northern Alberta.

Models: Models initialized fairly well in terms of 500 mb heights
against the respective raobs across the state, around 1 to 2 dm to
low in terms of the observed H5 heights. The 02/00Z deterministic
models are in good agreement through 90 hours, or through next
Sunday, before they begin to diverge on some of the smaller scale
features in the upper flow.

Overall larger scale pattern will remain unchanged into early next
week with broad ridging over the Bering Sea and troughing from
northwest Canada through mainland Alaska, keeping seasonably cold
temperatures across the state. H85 temps will range from -16 to
-18 over the west coast and interior to -20 to -25 over the
central and east interior into Sunday. The coldest air of the snap
looks to begin on the arctic coast Saturday night, dropping south
into interior Alaska into Sunday, with H85 temps dropping as cold
as -30 to -35 below near the ALCAN boarder Sunday and Monday. Lows
for interior valleys over the next several nights are expected to
fall between 25 to 35 below, with several 40 below readings
expected in the traditional cold locations. Diurnal temperature
swings are expected to range between 20 to 35 degrees.

A series of shortwaves will move through the state from northwest
to southeast. The first wave will move out of the Brooks Range
early this morning into the central Interior, and will have little
impact weatherwise south of the Brooks Range; other than some
scattered clouds and flurries for parts of the western Interior.
This feature will continue to promote north to south gap flow
through Alaska Range passes into Friday morning. Low wind chills
will remain a concern in passes through at least this morning,
mainly south of a line from Denali Park to Black Rapids. Wind
Chill advisories will continue for zone 225 and 226 until noon
today as wind chills will drop to around 45 below before improving
with diurnal warming. Advisories may need to be extended through
tomorrow morning, but elected not to do so at this time as wind
chills have remained just below criteria through early this
morning. A second more vigorous shortwave will round Bering Sea
ridge and drop into western Alaska Friday night into Saturday,
merging with yet another short wave that will round northern
Canada upper low. These features will bring with it more
widespread cloud cover along with a chance of snow and flurries
with light accumulations expected. This will also act to further
carve out existing trough, bringing lower heights and the coldest
air of this particular spell. The GFS is much more bullish with
deepening the trough compared to the ECMWF/Canadian, and prefer
the latter solutions given previous run to run consistency and
latest NAEFS 500 mb heights.

North Slope and eastern Brooks Range: Maintained all wind
chill/winter weather advisories for zones 201, 203 and 206, and
the blizzard warning for zone 204. Wind chills should improve this
morning in zone 201 and elected not to extend the advisory. The
pressure gradient for the eastern arctic coast is expected to
strengthen today through tonight, as smaller short wave impulses
round around the western periphery of Canadian Archipelago upper
low, and associated surface low drifts south toward the coast.
Periods of light snow and blowing snow will continue from the
eastern arctic coast to the eastern Brooks Range through at least
tomorrow morning, with poor visibility and low wind chills in zone
204 continuing into Friday night. Blizzard conditions there now
will significantly worsen late tonight through Friday, as
terrain-enhanced west winds are expected to gust to around 70 mph
as the pressure gradient tightens. Conditons overall look to
improve on Saturday, as strong cold front sweeps through the North
Slope from the north helping to diminish the pressure gradient
and snowfall in its wake.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory for AKZ201-AKZ225-AKZ226.

Blizzard Warning for AKZ204.

Winter Weather Advisory for AKZ203-AKZ206-AKZ218.

Gale Warning for PKZ245.

Brisk Wind Advisory for PK235-PKZ240.

&&

NTS MAR 17