High Wind in Alaska, August 26, 2023

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
229 PM AKDT Sat Aug 26 2023

.SYNOPSIS...
An area of low pressure is moving up through the Yukon Delta this
afternoon and will move into the western Brooks Range tonight.
Widespread rain showers will persist across the west coast and
western interior through Sunday. The central and eastern Brooks
Range will see more persistent rainfall with an additional 1 to 2
inches through the weekend so a flood watch has been issued
especially with the rain falling on saturated ground. A chinook
event continues in the Alaksa range with gusts to near 60 mph in
the foothills and passes, especially in areas west of Delta
Junction down towards Tok.

&&

.DISCUSSION...
Current Analysis...
A surface low has moved ashore on the Yukon Delta this morning and
so far has been maintaining its strength as it moves north. A few
thunderstorms were associated with it this morning but so far
there has not been any cloud flashes detected since the center of
the low has moved ashore. Heavy rain showers are still associated
with the center of the low. There are a couple of shortwaves in
the Bering Sea, one near St. Paul and another up towards Gambell.
A dry slot has pushed into SE AK and is pushing into the Western
and Central Interior this afternoon. Across the SE interior, a
chinook event has kept the region dry with strong winds in the
Alaksa Range and into the foothills. The rest of the central and
eastern interior have seen some spotty high based showers. High
pressure over the Arctic ocean has lead to persistent strong NE
winds across the North Slope down towards the Bering Strait.

Model Discussion...
The global deterministic models are handing the long wave pattern
well over the next few days but struggling with the shortwaves
more than usual in the near term. None of the models are picking
up on the 2 shortwaves that are visible in the Bering Sea on water
vapor imagery. Upper level flow does have strong divergence at 250
mb over the West Coast so the existence of those shortwaves are
likely a result of the strong synoptic lift. The strong lift will
also likely maintain the surface low moving north through the
Western Interior better than what the models have though the trend
in MSLP has been to a stronger low near the Brooks Range tonight.
As the low crosses the Brooks Range, the models vary on how they
handle the reformation of the low. The NAM is likely handling it
the best with a new low forming on the occluded front just north
of the arctic coast Sunday night.

Central and Eastern Interior...
A chinook event is continuing for the central and eastern Alaska
Range with strong SW flow at 700 mb. With the low over the Yukon
Delta moving towards the Brooks Range this afternoon, flow at 700
mb will increase to over 50 knots with heavy windward
precipitation. Gusts through the passes and right at the foothills
will be approaching 60 mph tonight and tomorrow. The 700 mb winds
do not slacken off until the surface low gets north of the Brooks
Range late Sunday night into Monday. For the rest of the central
and eastern interior, the weather will be cloudy with intermittent
showers. The farther north towards the Brooks Range, the coverage
and intensity of showers will increase especially tonight through
tomorrow morning. Once the low is north of the Brooks range,
cooler westerly flow develops though chances of showers continue.

West Coast and Western Interior...
Low pressure moving north from the Yukon Delta will move into the
eastern Brooks Range tonight. Heavy rain showers near the center
of the low are moving through the western interior with lighter
showers and stratiform rain along the west coast. With assisted
lift from several shortwaves off the west coast in the Bering Sea,
a swath of heavier rainfall is possible from the Norton Sound up
into the Brooks range with an additional 0.5 to 1.5 inches. There
is greater confidence that areas just south and in the eastern
Brooks Range could see closer to 2 inches by Monday morning.

North Slope and Brooks Range...
The main concern is the heavy rain in the Brooks Range. A deep
plume of moisture advects in with the low moving north along the
west coast that will bring steady rain late today through Sunday
evening. Areas that have already seen an inch plus of rain in the
Central and Western Brooks Range will see an additional 1.5 to 2
inches with locally higher amounts. Rain will spread through the
rest of the north slope tonight into Monday morning but with less
moisture left with the system, rainfall amounts will be lighter
north of the Brooks Range. A new surface low will form along an
occluded front off the Arctic Coast Sunday night and deepen Monday
with a cold front moving through the arctic coast with strong
winds.

Extended Range Days 4-7...
The long wave trough will likely begin to flatten out with upper
level flow becoming more westerly. Clouds and showers persist for
the coast through western interior through the end of the week.
The remnants of typhoon Damrey towards the end of the week with
more ensemble members bringing the low towards the SE Bering sea.
Members that have a more westerly track towards the central
Bering sea have the strongest extratropical transition with weaker
solutions farther east likely due to a difference in amplitude of
the upper level flow between the ensembles.

Coastal Hazard Potential Days 3 and 4...
High Surf will continue along Bering Strait and St Lawrence
through Sun afternoon. High surf expected Shishmaref Sun, and at
Deering and Kotzebue Sun PM. High surf possible over the Eastern
Arctic Coast on Mon PM.

NW winds gusting 40 to 50 mph will continue from Point Hope to
the Bering Strait to Sat Lawrence Is through Sun AM, then turn NW
gusting 30-40 mph and move along the West Coast Sun PM

Gale force NW winds are expected to develop over the Eastern
Arctic Coast on Mon. This could cause high surf over the Eastern
Arctic Coast on Mon PM.

&&

.FIRE WEATHER...
The wet pattern continues for most of the region with an exception
in the SE Interior. Chinook flow will continue through Sunday with
gusts near 60 mph in the Isabel Pass as well as Mentasta Pass into
the foothills around and between the passes. Min RH will likely
stay above 40% in the regions with the higher winds. The chinook
comes to an end late Sunday into Monday morning.

&&

.HYDROLOGY...
Another 1.5 to 2.5 inches of rain is likely through tomorrow
night. The Koyukuk Basin west of the Dalton Highway, and the Kobuk
and Noatak Rivers and their tributaries will reach bankfull
levels Sunday with a slight chance of flooding early next week.

Heavy rain from 2 to 4 inches is possible through this weekend
along the south slopes of the Alaska Range, including the
headwaters of the Nenana and Delta Rivers. The Nenana and Delta
Rivers and may rise to near bankfull levels in some low lying
locations Sunday and Monday.

Expect rain amounts through Mon will be 0.50-1.00 inch across the
Northern, Central and Western Interior, the West Coast and North
Slope with about 0.25-0.50 inch over the Eastern Interior. This
will cause rises on most rivers through Mon.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...High Surf Advisory for AKZ213.
     Wind Advisory for AKZ223-225-226.
     High Surf Advisory for AKZ207.
     High Surf Advisory for AKZ209-210.
PK...Small Craft Advisory for PKZ801.
     Small Craft Advisory for PKZ802.
     Small Craft Advisory for PKZ806-807-811-817-850-853-854-856>861.
     Small Craft Advisory for PKZ812-813-816.
     Small Craft Advisory for PKZ814-815-851.
&&