Area Forecast Discussion
Issued by NWS Fairbanks, AK

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000
FXAK69 PAFG 182218
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
218 PM AKDT Mon Sep 18 2017

.DISCUSSION...

Models...Big picture wise there has been Good agreement in the
short term, first 36 to 48 hours. Beyond 36 hours or so divergence
starts growing and beyond 72 hours or so there are quite large
differences in the solutions. Solutions initialized well against
the 18/18Z surface analysis. For the short term will utilize a
equal blend for most elements with a lean toward the NAM
precipitation solution. Biggest challenge this time of year is
precipitation type as we transition to winter in Arctic locations.

Aloft at 500 hpa...Troughing remains in the vicinity of the
Dateline and extends south over the Chukchi Sea and south to
Nunivak Island. A shortwave over the Bering Strait will move east
over the area West Coast this evening, then northeast over the
eastern Arctic Coast into the Beaufort Sea Tuesday morning. The
longwave trough will continue to slide east with a 539 dam low
developing over the Seward Peninsula tonight and moving over the
middle Yukon Valley by Tuesday evening, and over Bettles by
Wednesday morning. The low will merge continue northeast and merge
with a 547 dam low that develops over Deadhorse Thursday
afternoon. A 545 dam low will develop over Kotzebue Sound
Wednesday afternoon and move southeast over the Nulato Hills by
Thursday afternoon at 543 dam. A 539 dam low over Kodiak Island
will move southeast across the Gulf of Alaska. Ridging extending
north over the Central Aleutians will continue to build with 570
dam heights over the Alaska Peninsula rotating northeast over the
Gulf of Alaska by Wednesday evening with weak ridging extending
north over the southeast Interior. At 850 hpa...Zero isotherm lies
from point Barrow to Selawik to King Salmon and will move east to
lie from Kuparuk to Healy then southwest by Tuesday morning. By
Wednesday morning it will lie from Old Crow YT to Delta Junction
then southwest. The -10 isotherm will push south as well and will
be over the northwest Arctic Coast by Tuesday morning, and by
Wednesday morning it will be over most of the Arctic Coast.

Surface...Broad area of low pressure over the state with several
minor lows floating around. A 1004 mb low over the Gulf of Anadyr
will move east to St Lawrence Island tonight dragging cold air
south. The broad area of low pressure over mainland Alaska will
be replaced by weak high pressure in the eastern half of the
state. By Tuesday morning the low over St Lawrence Island will be
over Norton Sound at 1007 mb, and weak high pressure will build
to the north and south of the low over mainland Alaska with weak
high pressure to the east. The low slows Wednesday evening over
eastern Norton Sound, and a 1021 mb high develops over the western
Brooks Range and moves over Point Barrow. To the south and east of
the low weak high pressure will persist and push northeast over
the Alaska Range. The low will continue to push east into the
Western Interior By Wednesday morning, but will start falling
apart over Ruby, then merge with a low over the Aleutians. By
Thursday afternoon a broad area of low pressure will extend from a
996 mb low over the Central Aleutians to the southern Yukon
Territory, remaining primarily south of the Alaska Range. To the
north a ridge of high pressure will extend from the northwest
Bering Sea across the Gulf of Anadyr and the Arctic Coast to
Banks Island.

Arctic Coast and Brooks Range...Not a lot of change expected
tonight, but the rain will be changing over to snow for sometime
Tuesday morning as cold air streams in from the northwest. Expect
some patchy dense fog along with the change over to snow during
the morning Tuesday. No significant snowfall is expected with the
system, but Brooks Range locations could see 2 to 4 inches over
the next couple days. Winds west to northwest increasing to 10 to
20 mph for most areas. Temperatures across the area falling below
freezing.

West Coast and Western Interior...A bit of clearing this evening
then clouding over again with another round of rain which will be
heavy at times. Rainfall amounts will range from around 0.10 inch
around along the Chukchi Sea Coast to possibly over 1.00 on the
northern Norton Sound Coast and the Bendeleben Mountains on the
Seward Peninsula. The Noatak and Kobuk River Basins are not
expected to get any significant additional rainfall at this time,
but with rivers running near bankfull it will not take too much
rainfall for problems to pop up. With the low moving over Norton
Sound, winds will be all over the dial with wind speeds increasing
to 10 to 20 mph tonight, then diminishing a bit Tuesday.

Central and Eastern Interior...Cloudy, some light rain around the
area tonight. Cold air moving over the area Tuesday night will
bring potential for snow at higher elevations, so Cleary Summit,
Murphy Dome, and other elevated locations could see a dusting that
will melt off fairly rapidly. In Denali NP, along the road at
higher elevations, expect snow Tuesday night and Wednesday that
may impact travel on the Denali Road. As can be expected,
temperatures will be falling through the week with the coolest
temperatures Thursday. Patchy fog along the rivers and near
lakes, but not expecting at any extensive dense fog coverage.
Light east winds becoming west to northwest at 5 to 15 mph Tuesday
and Wednesday.

&&

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

&&

.Hydrology...Flood Advisory remains in effect for Kobuk to Kiana
and vicinity. Expect high water to continue around Huslia to
Hughes, but it will be slowly falling.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Flood Advisory for AKZ208-AKZ217.

Small Craft Advisory for PKZ200-PKZ210-PKZ215-PKZ220.

&&

$$

SDB SEP 17



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