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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska
525 PM akst Thursday Mar 5 2015

Discussion...
short term...models are in good agreement with the position and
track of features during the next 24 hours. Strong westerly flow
across Alaska will bring active weather to the forecast through
Friday and beyond. A short wave aloft embedded in the westerly
flow is currently over the western interior will move east into
the Yukon territory on Friday. Surface low pressure associated
with this feature will bring several inches of snowfall tonight
and Friday to much of the interior before exiting the forecast
area. Snow will taper off from west to east beginning this evening
with some lingering snow remaining over the eastern interior on
Friday.

On the heels of this first weather system is a much stronger low
currently over the western Bering Sea which will move to Saint
Lawrence Island by Friday evening. The associated weather front
will sweep into the West Coast Friday...spreading heavy snow from
the Yukon Delta north to the Brooks range and into the western
interior. Models indicate this will be primarily a snow event
with only a chance for some mixed precipitation in the lower Yukon
River Valley. Warnings for heavy snow and local blowing snow have
been issued for the West Coast and western interior.

Long term...Friday night through Sunday...main focus will be on
expected strong storm system...which will serve as a heavy snow
maker for many locations over west and west interior...with decent
accumulations expected for the central and eastern interior.

Aloft at 500 hpa...505 dm low centered near the Gulf of Anadyr
Friday evening...with associated negatively tilted trough with axis
extending southward toward St. Paul island will slide east onto
Mainland Alaska late Friday night...with the trough axis centered
from Kotzebue to King Salmon Saturday morning. This wave will
open/shear out as it moves northeastward into northeastern Alaska
during the day on Saturday. Meanwhile...a secondary short wave with
508 dm low will move off the chukotsk peninsula Saturday
evening...with the low centered near Mountain Village by Sunday
afternoon...and the associated trough axis centered from Nuiqsut
southwestward to Scammon Bay. This wave will act to reinforce the
existing trough...yielding a major pattern change in terms of
temperatures for the forecast area for early next week.

At the surface...984 mb low centered in the Gulf of Anadyr will move
eastward across the Bering seas on Friday...centered around 30 miles
west of Saint Lawrence Island by Saturday evening at 987
mb...further weakening to a 993 mb low by Saturday morning centered
near Kotzebue. The low will further weaken as a broad trough as it
passes to the south of the Brooks range Saturday. High pressure will
develop over eastern Siberia on Saturday...strengthening to 1045 mb
by 18z Sunday.

West Coast and western interior...deep west to southwest flow over
the Bering Sea ahead of the approaching trough will bring strong
moisture transport to the West Coast and western interior...with
naefs ensemble guidance suggesting integrated water vapor transport
between 5 to 7 Standard deviations above normal Friday into
Saturday. Dynamics look very good with good lifting support from
approaching wave and upper level divergence from a strong 500 hpa
jet streak...helping to support decent dedridic growth as well.
Everything still looks good for a good 6 to 12 inch snow event
across western Alaska...with the higher amounts favored in areas
with terrain enhancement including the Nulato Hills and for the
inland Seward Peninsula. Winds off the deck look strong as
well...between 30 to 40 knots at 925 mb. This will create blowing and
drifting snow for most places...although the strong winds aloft
won't be fully realized at the surface given neutral to weak warm
air advection regime. The most significant snow and blowing snow
will gradually diminish on Saturday...although snow will continue to
fall through the weekend under the deepening broad upper trough.
Temperatures will begin to fall on Sunday under strong cold air
advection...with temperatures expected to run at least 10 to 15
degrees below normal for the first half of the work week.

North Slope...not too much in the way of concerns here...as the
weakening system will keep the heavier snows south of the Brooks
range. Expecting some mainly light snow or snow showers to persist
here through the weekend. Winds do not look to be too
strong...generally 20 miles per hour or less through Sunday. Main issue will be
falling temperatures Sunday...ranging from around 10 to 20 below
through the first half of the work week. Sufficient north to
northwest winds will allow wind chills to dip between 40 to 50 below
at times.

Interior...snow will begin to move into the interior zones Friday
night...continuing into the day on Saturday. Again with the
weakening dynamics as the upper level wave opens and surface low
weakens...not expecting snow amounts to be as heavy...but still
appreciable for early March. Envision advisory level amounts for
many interior zones as deep southwesterly moisture transport still
looks good. Will have to watch for the potential for heavy snow over
the eastern Alaska Range...where moist southwest flow aloft will be
most perpendicular to the range here Friday night into the day on
Saturday. The other concern in addition to the accumulating snow
will be the potential for blowing and drifting snow late Saturday
into Saturday night as strong 925 mb winds between 30 to 40 knots
develop over the lower Tanana Valley...extending northeastward into
the White Mountains and Yukon Flats. Could see some travel concerns
over summits in zones 221 and 220...as well as the greater Fairbanks
area and Parks Highway as gusty Post frontal winds get mixed down to
the surface. However...impacts should not be worse than what was
seen last Saturday. Much cooler air will move into the interior for
early next week...with again temperatures running at least 10 to 15
degrees below average.



&&

Afg watches/warnings/advisories...
Winter Storm Warning for akz208-akz209-akz210-akz211-akz212-
akz213-akz214-akz215-akz216-akz217.

Gale Warning for pkz210.

Brisk Wind Advisory for pkz200-pkz210-pkz215-pkz220.
&&

$$

Mar 15

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