High Wind in Alaska, September 13, 2017

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
440 AM AKDT Wed Sep 13 2017

.DISCUSSION...

Models...Excellent agreement in the short term with the big
picture. Waves continue to be embedded in the strong southwest
flow over the west coast making it hard to differentiate them, and
determine how strong they will be and the timing of the strongest
waves. Models initialized well against the 13/06Z surface
analysis. Long fetch of moisture is being pulled into the flow,
over the West Coast and Western Brooks Range, from the north
Pacific. Will lean a bit more on the NAM again today since it
handles the downslope effect better, and handled the winds better
yesterday.

Aloft at 500 hpa...A 520 dam low remains high in the Canadian
Archipelago with troughing extending southwest across the northern
Arctic to a 525 dam low near Wrangel Island and a 520 dam low over
the northern Gulf of Anadyr. Several shortwaves are moving
north in the flow over the west coast with a relatively strong
shortwave moving over the Brooks Range around noon today. Another
strong shortwave will move to the Brooks Range on Friday morning.
Several weaker shortwaves will be moving through the flow, but
timing will be impossible to determine. Ridging has built north
over the AlCan Border this morning with 552 dam heights reaching
north over MacKenzie Bay. The ridging will continue to slide east
today over Canada. Ridging will build west over the Western
Interior this afternoon and evening as it rotates over the main
ridge axis in advance of the next shortwave. Ridging will build in
slightly stronger behind the shortwave Friday. A 548 dam low
will develop over Cook Inlet Thursday evening, and move over the
central interior Thursday night and over the Yukon Territory
Friday afternoon. At 850 hpa...Zero isotherm lies from Wainwright
to Brevig Mission to Nunivak Island this morning and will move
east to lie from Nuiqsut to Selawik to Scammon Bay by Thursday
morning. The zero isotherm will back a little by Friday morning to
lie from Point Barrow to Kotzebue to Emmonak.

Surface...Weak ridge of high pressure over the Eastern Interior
continues to hold on, but will weaken as the 1029 mb high south of
the Gulf of Alaska moves south and weakens a bit. Weather front
remains over the west coast and will slide a bit to the east as
the main ridge axis slide east. Front over the Arctic coast will
move offshore about 100 nm and stall. A 990 mb low 200 nm
northwest of Point Lay will move west to 50 nm north of Wrangel
Island by Thursday morning. The front over the Western Interior
will remain stationary and weaken Thursday as it dissipates.
Trough will set up to the west by Friday morning extending from
the low near Wrangel Island to a 989 mb low in the Gulf of Anadyr
to a 977 mb low 100 nm west of St Paul Island. Leeside troughing
continues north of the Alaska and Brooks Ranges. Expect more
enhanced downslope winds in the Central Brooks Range today as the
shortwave aloft moves through the area in the early afternoon.
Winds north of the Alaska range not quite so strong. Tight
gradient persists into the afternoon before relaxing, but expect
it to tighten back up along the Alaska Range on Friday.

Arctic Coast and Brooks Range...Cloudy with some light rain.
Strong winds on the north slopes of the Brooks Range again today
with gusts around 60 mph possible, so will maintain warning for
zone 205 and issue warning for zone 206. Plains and Coastal areas
will not see significant winds, but breezy conditions will
continue. Temperatures a bit warmer again today with the south
flow over the area.

West Coast and Western Interior...Rain, rain and fog, and more
rain again today. Strong southwest flow continues to pull
moisture from the north Pacific. Heaviest rainfall continues to
be in the Upper Kobuk and Noatak Valleys, and the Bendeleben
Mountains on the Seward Peninsula. Rainfall amounts the past 24
hours ranged from 0.25 to around 3.50 inches, and another 0.25 to
1.50 inches is possible today and tonight. Patchy fog may impact
visibility at times. Winds will be dependent on the location of
the front with winds to the west of the front from the northwest
to north at 5 to 15 mph and winds to the east of the front from
the east and southeast at 10 to 25 mph.

Central and Eastern Interior...Partly sunny again today from
Fairbanks east. Rain to the west of Fairbanks, with mainly
sprinkles and only a slight chance of rain from Fairbanks
southeast today as downslope will once again impact precipitation
amounts in the Eastern Interior. Strong pressure gradient
continues across the Alaska Range so will maintain the Wind
Advisories for zones 225 and 226 for passes and vicinity.

&&

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

&&

.Hydrology...Flood Advisory remains in effect for many western
areas as rain continues to fall today with additional rainfall
amounts of 0.25 to 1.50 inch today and tonight. Seeing some rises
in the rivers and sand bars will continue to disappear as waters
rise with back sloughs also filling up. Some small streams from
the Seward Peninsula to the Western and Central Brooks Range have
risen up to 2 feet in the last 24 hours and will continue to rise
to bankfull with the potential for some localized flooding.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Flood Advisory for AKZ208-AKZ209-AKZ210-AKZ211-AKZ212-AKZ213-
AKZ216-AKZ217.

Wind Advisory for AKZ216-AKZ217-AKZ225-AKZ226.

High Wind Warning for AKZ205-AKZ206.

Small Craft Advisory for PKZ200.

&&

SDB SEP 17