000
FXAK69 PAFG 222256
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
256 PM AKDT Thu Jul 22 2021

.SYNOPSIS...
Warm over the Interior and cool out west as ridging holds over the
eastern half of the Mainland. Thunderstorms will be active the
next couple days across the Eastern Interior with the threat for
heavy rain across drought stricken areas, including the Tanana
Valley. Gradual cooling through Sunday as the ridge weakens over
the Eastern Interior.

&&

.DISCUSSION...

Upper Levels and Analysis...
A closed blocking high is the dominant feature over the Interior
with the high center over the eastern Yukon Flats. The heights at
500 hpa are approximately 565 dam, which is not too shabby but not
overly high for summer. Easterly flow aloft is bringing in subtle
shortwave troughs from the Yukon with the first moving into the
Fortymile Uplands. Out west there is a cold upper level trough
stretching from Wrangel Island all the way through Bristol Bay
into the North Pacific. At the surface a thermal trough is
situated over the Yukon Flats with pressure around 1004 mb. There
is another low in the Gulf of Alaska with a surface high over the
Arctic.

Model Discussion...
The models are in good agreement with the general pattern but less
agreement with precipitation as an easterly wave moves through the
southeast Interior over the next couple days. In general expecting
heavy rain from the Fortymile Uplands to the Eastern Alaska Range
through tomorrow morning as easterly wave one moves into the
Interior. Tomorrow is less certain but it seems likely that a
stronger easterly wave moves in with thunderstorms forming over
much of the Eastern Interior to the eastern Brooks Range. Heavy
rain will be possible from the Eastern AK Range to Fairbanks and
the White Mountains. For now a blend is favored to average out the
high and low model differences in terms of precipitation. Long
story short, wetter and cooler with increased thunderstorm threats
next couple of days.

Central and Eastern Interior...
Easterly wave number one is moving west through the Fortymile
Uplands. Expect scattered thunderstorms to form there then drift
southwest into the Eastern AK Range tonight, bringing moderate
rainfall up to an inch along the north facing slopes. This wave
will stall out over the Eastern AK Range tonight and tomorrow
morning, before a stronger wave moves in Friday afternoon. It is
looking like an active thunderstorm day from the Tanana Valley to
the Fortymile Uplands and north to the White Mountains. Scattered
thunderstorms with the potential for locally heavy rain and
frequent lightning will develop late afternoon with the potential
for heavy rain to go well into the overnight. Right now the
heaviest rainfall is expected across the Alaska Range and into the
Tanana Valley, where two day totals will be in the range of
0.5-2", heaviest in the AK Range.

The ridge breaks down this weekend with showers and thunderstorms
retreating to closer to the ALCAN late Saturday and then exiting
completely on Sunday.

West Coast and Western Interior...
A trough over the Bering Strait will gradually shift inland
bringing intermittent showers and light rain to most of the
region. The first trough exits on Saturday with another low moving
in from Siberia, bringing more rain to the Seward Peninsula north,
with the heaviest rain over the Noatak/Kobuk Valley as it moves
inland Sunday.

North Slope and Brooks Range...
Light onshore flow will keep fog and stratus over the immediate
Arctic Coast through Friday. A low will move over the western
Arctic, bringing rain and showers to the North Slope and Brooks
Range Friday and Saturday. On Sat afternoon, the low will move
over the eastern brooks Range, and there will likely be a good
amount of thunderstorms that move off the Brooks Range and into
the arctic waters. Some storms may be strong and will produce
locally heavy rain east of Prudhoe Bay. Another front will bring
more rain to the western Arctic on Sunday.

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

&&

.FIRE WEATHER...
Active fire weather the next couple days over the Interior with
scattered thunderstorms today over the Fortymile, and again
tomorrow across a wider swath from Fairbanks east to the ALCAN.
This will be in conjunction with a stronger easterly wave aloft.
This will also produce heavy rainfall over the same areas through
Saturday. The thermal trough slowly erodes after Saturday with
cooling temps and increasing min RH values over the Interior,
along with a significant reduction in thunderstorm activity.

&&

.HYDROLOGY...
Two easterly waves, one tonight and another tomorrow, will bring
heavy rain to the Eastern AK Range and areas to the north.
Between 0.50-2.00 inches of rain possible is SE of Fairbanks
tonight through Sat with the heaviest amounts along the Alaska
Range. This could lead to small stream flooding along the Alaska
Range Fri and Sat, including near Denali Park. Beyond this,
larger stem rivers are running very low so no river flooding is
anticipated.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning for AKZ220-AKZ222-AKZ224.
&&

$$

AHSENMACHER JUL 21