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000
FXAK69 PAFG 202255
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
255 PM AKDT Tue Jul 20 2021

.SYNOPSIS...
The tale of troughing across the West Coast and ridging across the
Interior will continue to play out for much of the week. This
afternoon will be the warmest of the week, with cooler
temperatures expected on Wednesday. Shower activity persists from
Utqiagvik south across the Brooks Range and along the West Coast,
with an additional quarter to half an inch of rainfall possible in
the favored upslope areas through Wednesday. Widespread isolated
thunderstorm activity this afternoon and evening will shift
eastwards Wednesday and be focused on the eastern and central
Interior with scattered thunderstorms possible along the AlCan
border.

&&

.DISCUSSION...
Upper Levels and Analysis...
Aloft, at 500 mb a long-wave trough extends south over the Chukchi
Bering seas and ridging is centered over the Northwest Territories
and the Yukon. On Wednesday, a shortwave will rotate along the
southern periphery of the trough and east across Bristol Bay,
helping to briefly weaken and nudge the ridging eastward. By
Thursday morning however, the shortwave has moved into the Gulf of
Alaska and ridging rebuilds across the eastern half of the state.
The overall pattern of troughing across the West Coast and ridging
across the Interior will persist into the weekend.

North Slope and Brooks Range...
A surface low is west of Kivalina this afternoon with a front
extending eastward across the North Slope and a cold front
stretching southeast. The front across the North Slope will
largely remain stationary through Thursday and weaken. This will
bring rain to the Brooks Range and most locations from Utqiagvik
west. Lower rain chances expected for the eastern Arctic coast.
Ahead of the cold front this afternoon, isolated thunderstorms
possible this afternoon and evening. Wednesday, thunderstorm
chances confined largely south and east of Umiat. Onshore
northeasterly winds will bring in areas of fog and downward
trending temperatures.

West Coast and Western Interior...
A surface low is north of the Seward Peninsula this afternoon
with a front extending eastward across the North Slope and a cold
front extending southeast across Norton Sound to McGrath. This
low will lift to be west of Point Hope tonight, while the front
across the North Slope remains stationary through Thursday. The low
finally lifts north away from the coast Friday. This will bring
significant rain to the Brooks Range, Chukchi Sea coast, as well
as the Kobuk and Noatak valleys through Wednesday. Expect between
a quarter and half an inch of additional rainfall, with the
highest amounts in the favored upslope locations. East of the cold
front this afternoon and evening, isolated to widely scattered
thunderstorms are expected, primarily along a line from Galena to
Noatak and east. Scattered showers will accompany the cold front
as it weakens and moves eastward toward the central Interior
overnight. Temperatures will be trending downward behind the front
and highs will range from the upper 40s along the coast to the
mid 60s inland.

Central and Eastern Interior...
The warmest temperatures of the week are occurring this afternoon
with widespread temperatures at or above 80 degrees. Southerly
gap winds persist in the Alaska Range passes through tonight with
gusts into the 40 mph range. Winds will diminish late tonight and
Wednesday. Isolated to widely scattered thunderstorms this
afternoon and evening across much of the Interior are expected to
continue into tonight. On Wednesday, isolated thunderstorms
expected from Northway to Bettles and east. Models continue to
indicate strong instability along and east of the AlCan border
Wednesday afternoon and evening, though the strongest instability
stays east of the border, thus have maintained the scattered
thunderstorms along a line east of Chalkyitsik and Chicken during
the afternoon and evening hours Wednesday. Temperatures will trend
downwards Wednesday as cloud cover increases and high pressure
aloft gets temporarily shunted eastward. Temperatures climb a few
degrees again on Thursday.

Extended Period Forecast Days 4 to 7...Little change in the
extended forecast as troughing out west battles ridging in the
Interior. Generally warm and dry conditions from Fairbanks east
with some afternoon thunderstorms and showers possible, with cool
and wet conditions to the west.

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

&&

.FIRE WEATHER...
Isolated thunderstorm activity will extend from Galena north and
east and into the Arctic Plain this afternoon and evening with
widely scattered thunderstorms possible along a swatch from east
of Minchumina north to Hughes to the Upper Kobuk and Noatak Valley
to Bettles and across a swath from north of Tok to Central and
Eagle. A weather front on the West Coast will continue to spread
showers over the area with increased chances of wetting rain west
of Tanana. Warm and dry east of Tanana with near Red Flag
conditions this afternoon and evening near the Alaska Range to
Delta Junction as winds gust to around 40 mph and RH drops into
the 26 to 30% range. Thunderstorm activity will be focused across
the central and Eastern Interior on Wednesday with scattered
thunderstorms and LALs of 4 expected along the AlCan border from
east of a line from Chicken to Chalkyitsik. Widely scattered
thunderstorms expected from Arctic Village to Central to Chicken.
Winds outside of the Alaska Range will generally be south to
southwest and less than 15 mph. Minimum Relative Humidity values
Wednesday will range from the upper 20s in the upper Tanana Valley
to the lower 30s in the Yukon Flats to above 60 percent from
Tanana west. Overnight Relative Humidity recovery will be fair to
good east of Tanana, and very good to the west.

&&

.HYDROLOGY...
An additional quarter to half an inch of rainfall is expected
through Wednesday over the West Coast, western Interior, and
western North Slope, with the highest amounts falling in the
favored upslope locations. This additional rainfall will cause
rivers in those areas to rise late this week, but no flooding is
anticipated. For the latest river information go to
www.weather.gov/aprfc.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch for AKZ220-AKZ224.

Small Craft Advisory for PKZ225-PKZ230.

Brisk Wind Advisory for PKZ235.
&&

$$

JUL 21