Area Forecast Discussion
Issued by NWS Fairbanks, AK

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454
FXAK69 PAFG 192200
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
200 PM AKDT Thu Apr 19 2018

.DISCUSSION...
Cooler temperatures and windy conditions will be the primary
forecast concerns through the weekend. Otherwise, a quiet weather
pattern will persist across the forecast area into next week.
19/12Z model guidance in good agreement through Monday before
model solutions start to diverge, especially with the broad trough
and associated low centers over the Bering Sea next week.

Aloft...at H500, a strong shortwave rotating south around a low
over Banks Island will dig southwest towards the Beaufort Sea
coast this evening, then proceed south towards Norton Sound
through Saturday morning. By Saturday morning, this shortwave will
have formed into a closed 513 dam low pinching off from the parent
low situated over the Canadian Arctic Archipelago. This new low
will move south to be over Nunivak Island by Sunday morning.
Coincident with this strong shortwave, significantly colder H850
temperatures will spread southwest initially over the North Slope
this evening, then further south over the interior by tomorrow
afternoon. Coldest H850 temperatures between -14C approaching
Fairbanks and -25C over the eastern half of the North Slope will
be seen tomorrow. Meanwhile, 545 dam ridge of high pressure
centered along the International Dateline and over eastern Siberia
will slide south and weaken through late Saturday. Upper level
ridging will build back north over the eastern Interior late
Sunday and Monday. By the end of the weekend, H850 temperatures
will have recovered across much of the area, especially over the
southern Interior and Alaska Range where H850 temps around 0C are
forecast by Monday morning.

Surface...A 1024 mb ridge of high pressure extending from the
North Pole south over the Arctic Ocean will build south towards
the North Slope through Friday evening as a pair of lows in the
north Gulf of Alaska weaken and conglomerate into a trough that
will move north inland towards the Alaska Range tonight.
Sandwiched in between the pressure gradient will tighten across
the Interior and Brooks Range tonight and persist through late
Saturday. The trough will shift west through Sunday morning,
becoming inverted over Bristol Bay and becoming a closed low near
Nunivak Island by late Sunday. Northern Alaska will remain through
the weekend and into early next week between high pressure that
slides east into the Canadian Arctic Archipelago and broad low
pressure in the Bering Sea.

Eastern and Central Interior...The main story will be cooling
temperatures and developing snow showers and cloud cover this
evening and continuing into tomorrow. Temperatures will drop 5 to
15 degrees through tomorrow with highs struggling to climb into
the mid to upper 20s over the northern Interior up to the
freezing mark near Fairbanks. It will be warmer over the Upper
Tanana Valley where H850 temperatures will remain warmer.
Overnight lows will remain warmer due to cloud cover and
precipitation than otherwise under clear skies and maximum
radiational cooling. Precipitation type will remain all snow for
showers across the central and eastern interior tomorrow.
Expecting the snow to be more plentiful over the Alaska Range due
to upslope flow, where 4 to 8 inches are possible over the next 24
to 36 hours. As the trough shifts west tomorrow night, showers
will come to an end and skies will start to clear. Warm return
flow will develop Saturday evening, pushing warmer H850
temperatures north. This will reflect in temperatures rebounding
fairly quickly Sunday and will continue to warm into Tuesday where
daytime highs could flirt with the upper 50s to around 60
degrees. Gusty gap winds will develop in the Alaska Range Sunday
as a leeside trough develops and strengthens.

North Slope and Brooks Range...Areas of fog and stratus will
persist along the Beaufort Sea coast overnight tonight. Snow
showers associated with a southward moving shortwave will
continue into this evening, mainly from Deadhorse east, before
dissipating. Not much in the way of snowfall totals with these
showers, maybe around an inch or so. Will see mostly clear skies
starting tomorrow and into early next week as surface high
pressure builds south towards and over the coast. Tomorrow`s high
temperature will be 5 to 10 degrees cooler with overnight lows on
Saturday morning ranging from around 10 below zero on the western
Arctic Coast to around 20 below over the inland arctic plains.
Temperatures will rebound into Monday and then into above normal
values by Tuesday and Wednesday.

West Coast and Western Interior...The pressure gradient over the
Bering Sea north to the Chukchi Sea will tighten tonight with
gusty northeast winds between 20 and 30 mph expected. Will see
some blowing snow, but nothing that will significantly reduce
visibility. Similar to the other areas in the forecast area,
temperatures are expected to drop 5 to 15 degrees through
tomorrow. Temperatures will rebound Sunday into early next week.
As the surface trough rotates west, snow and rain showers will
develop Saturday into Saturday night south of Nome to Kaltag.
Chances for precipitation will continue into next week as this
area remains under the influence of a low off the coast.

Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...Snow and rain showers across much of the Interior
and Alaska Range will keep minimum relative humidity values above
35 percent tomorrow and Saturday. Slightly drier in the Upper
Tanana Valley on Saturday. Cooler temperatures Friday across the
Interior around 10 to 15 degrees cooler than what was observed
today. Winds will be primarily out of the Northeast through the
weekend, except for near and through Alaska Range passes where
south gap winds will develop this evening and continue through the
weekend. There is currently no threat of thunderstorm activity.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ200-PKZ210.

Heavy Freezing Spray Warning for PKZ210.

Brisk Wind Advisory for PKZ220-PKZ225.
&&

$$

LTH APR 18



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