Area Forecast Discussion
Issued by NWS Fairbanks, AK

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131
FXAK69 PAFG 242115
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
115 PM AKDT Wed May 24 2017

.DISCUSSION...

Models...Initialize well against the 24/18Z local surface
analysis, but as has been the trend, they diverge significantly
past 90 hours or so. Precipitation patterns relatively similar in
the short term. Models bringing in the cooler air aloft a bit
quicker and cooler, so better chances of snow at elevations as the
snow level gets dragged down Like yesterday, will lean on an even
blend which will make only minor adjustments to the current
forecast for the first 48 hours, then a means based forecast
beyond that due to the diverging solutions with this progressive
pattern.

Aloft...At 500 hpa...A 535 dam low in the northwest arctic will
dissipate near the dateline tonight. A 538 dam low over the
Northwest Territories of Canada continues to move east. Weak
ridging over the AlCan border is drifting east over the Yukon
Territory and will move over the Northwest Territories by Thursday
morning. A 550 dam center over the Beaufort Sea will drift over
Banks Island tonight, then move north into the high arctic. A 519
dam low over St Matthew Island will split with a 520 dam low
moving over the Seward Peninsula this evening, then over the
Chukchi Sea by Thursday morning, while the low over St Matthew
Island will move east over the lower Yukon Delta by Thursday
morning at 524 dam then dissipate by afternoon. A shortwave
associated with the lows is over the southwest mainland this
afternoon and will lie from Nome to Lake Minchumina to Yakutat
this evening, then across the interior Thursday morning to be over
the Brooks Range and AlCan Border by noonish Thursday. There
appear to be several more wrinkles in the flow, but timing them is
virtually impossible. Weak ridging starts building back over the
eastern interior late Friday. At 850 hpa...Zero isotherm lies from
Nuiqsut to Kodiak City with warmest temperatures to the east.
Tonight the northern half will move toward Barrow while the
southern half moves east and by Thursday morning it will lie from
Barrow to Old Crow YT to Glennallen. This will allow cold air
aloft to move into southern interior locations bringing cooler
temperatures to the region and pushing the snow level down. The
zero isotherm will be over the AlCan border by late Thursday. It
will start moving back west as the ridging builds back over the
eastern interior Saturday.

Surface...Arctic front remains over the northwest coast today but
will push offshore for a few hours before being pulled back south
over the area. A broad low with a 993 mb center over the Seward
Peninsula lies over the west coast with troughing extending east
over the interior to the Yukon Territory. As the low move over the
Chukchi Sea, the tight pressure gradient persisting across the
Alaska Range today will relax tonight and winds will diminish. As
the trough aloft moves through the area a 1005 mb low will develop
at the surface over the Kuskokwim Valley to the upper Yukon Flats
late tonight. The trough over the interior will swing north
Thursday morning and be over the arctic coast by Thursday
afternoon with the low over the Yukon Flats moving to the eastern
arctic coast as it deepens to 1000 mb. Ridging will build in
behind the front with a 1013 mb high developing over the Copper
River Basin and moving into the interior as ridging continues to
build over the AlCan Border. Troughing will persist over the
Chukchi Sea and eastern Bering Sea with southwest flow in the
coastal areas.

Arctic Coast and Brooks Range...A little bit of everything
weather on the arctic coast the next couple days. Some patches of
sunshine this evening, low stratus ceilings, areas of dense fog,
rain, snow, chance of freezing rain, about the only thing we will
not see is strong winds. As the low in the Chukchi Sea moves north
the front will move across the area. Some areas are already
getting a little snow and most areas will see up to 3 inches of
fresh snow by Friday morning. There is a chance of freezing rain
tonight through Thursday morning as the freezing level rises to
around 4500 ft from Barrow east over the coast and eastern arctic
plain. Cooler air moving over the area Thursday afternoon.
Temperatures a bit warmer tonight, then cooling. Winds generally
northeast to east at 10 to 25 mph from Barrow east while winds on
the northwest coast will be rotating around as the low moves north
across the Chukchi Sea.

West Coast and Western Interior...Going to be pretty wet the
next couple days with some accumulating snow on the Chukchi Sea
coast, at higher elevations of the Seward Peninsula, and along the
south slopes of the western Brooks Range. There may even be some
snow mixing in at lower elevations further south for a short
period as a band of colder air moves through the area. Areas with
accumulating snow will see 2 to 5 inches. Rainfall amounts will
range from around 0.25 to 0.75 of an inch through Friday
afternoon. Some isolated thunderstorm activity possible, but with
cooling temperatures and strong wind shear aloft, it should be
suppressed quite a bit. Winds on the western Alaska Range will
diminish late this evening as the pressure gradient relaxes across
the area.

Central and Eastern Interior...Cloudy conditions will prevail
through Thursday with increased shower activity and rainfall
amounts up to 0.50 inch through Friday afternoon. The main focus
will be on the western Alaska Range and Denali Park as location
above 1000 feet or so from Polychrome Pass west will see 6 to 11
inches of snow by Friday morning so will be keeping the Winter
Weather Advisory out. Some snow has already fallen, and snow
showers will continue and pick up in intensity late in the
afternoon and overnight. Chinook winds blowing pretty good near
the passes and around Delta Junction will be shutting off this
evening as the pressure gradient relaxes across the Alaska Range
so will no change the timing of the current Wind Advisories for
those areas. Temperatures in the interior cooling as cold air is
pushed east across the state into the area tonight, then warming
on the weekend as ridging build north of the AlCan border.

&&

.FIRE WEATHER...A little wetter and a little cooler with elevated
dew points and winds diminishing will produce unfavorable fire
conditions. Thunderstorm activity will also be suppressed through
at least Friday.

&&

.HYDROLOGY...Rivers and streams in the interior are starting to
go down after the last rain, and with more on the way expect them
to start rising a bit on Friday, but do not see any issues at this
time. Current forecasts keep them below any action stages. No
updates on the arctic river situation as breakup continues its
slow steady march.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Wind Advisory for AKZ223-AKZ225-AKZ226-AKZ227.

Winter Weather Advisory for AKZ225.

Small Craft Advisory for PKZ200-PKZ210-PKZ220-PKZ225.

Brisk Wind Advisory for PKZ245.

&&

$$

SDB MAY 17



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