Scientific Forecaster Discussion
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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
547 am akst Wed Mar 1 2017
aloft: the Mar 01/00z 500 mb pattern shows broad troughing over
Mainland Alaska with a 508 dm low centered over Prince William
Sound. This trough is actually an extension of polar vortex that
is located over the Canadian archipelago at 474 dm. West of this
low a 515 dm short wave was rounding the western periphery, located
around 750 miles northwest of wrangel island in the east siberian
sea. A ridge of high pressure at 557 dm was located over the
western Bering Sea, with ridging extending northwestward into
Surface: 01/06z analysis shows a large 995 mb low centered over
the eastern Gulf around 285 miles west of Sitka. To the west,
strong high pressure at 1045 mb was located over the Gulf of
Anadyr, with ridging extending eastward across the Brooks range.
Low pressure of 993 mb was seen over the far east Beaufort Sea, or
around 260 miles north of Banks Island.
Models: models initialized well in terms of 500 mb heights against
the respective raobs across the state. The 01/00z deterministic
models are in fairly good agreement through 120 hours, or through
next Sunday, before they begin to diverge on some of the smaller
scale features in the upper flow.
Amplified pattern with broad troughing will remain over the state
through this weekend into at least the first half of next week,
as a series of short waves will reinforce the upper trough, with
ridging remaining in the Bering Strait. The past few model runs
have shifted the ridge axis further east, suggesting overall
higher heights than earlier predicted over the state and keeping
the core of the coldest air into western Canada, something that
will need to be watched over the next several days. Needless to
say seasonably cold temperatures will persist into early next
week. 850 mb 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. Winds over the interior south of the Brooks range will
gradually weaken today as low pressure in the Gulf shifts slightly
southward and pressure gradient weakens. 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 dropping down the western periphery of the
broad upper low will have little impact on the area south of the
Brooks range, with periodic bouts of flurries or snow showers
mainly for the West Coast and western interior for the remainder
of the week, which will convolute the temperature forecast at
times due to cloud cover. North to South Gap flow through Alaska
Range passes is expected to continue into Thursday morning. Low
wind chills will remain a concern in passes through at least
tomorrow morning, and opted to extend wind chill advisories for
zone 225 and 226 until noon tomorrow as wind chills will drop to
around 45 below tonight and tomorrow morning again before
improving with diurnal warming today.
North Slope and eastern Brooks range: extended winter weather
advisories for 203 and 206 until noon Friday, and maintained
Blizzard Warning for zone 204 through Friday night. There will be
a lull in the activity today with relatively improved visibility
and warmer wind chills. A series of short waves and associated
surface weather fronts will drop out of the high Arctic over the
North Slope for the next several days, the first of which will act
to tighten the pressure gradient and bring a another round of
light snow and blowing snow late tonight into Thursday, mainly
east of Barrow. Wind chills will fall between 50 to 55 below over
the North Slope and through passes in the Brooks range late
tonight through Friday morning. Will likely need to expand wind
chill or winter weather advisories for remaining North Slope zones
today or tonight, depending to what effect snow and blowing snow
will play a role (which case would require a wwa).
Wind Chill Advisory for akz225-akz226.
Blizzard Warning for akz204.
Winter Weather Advisory for akz203-akz206-akz218.
Gale Warning for pkz245.
Brisk Wind Advisory for pkz240.