Flood in Alaska, May 22 to 24, 2019

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
558 AM AKDT Wed May 22 2019

.DISCUSSION...

Synopsis...Another beautiful day in the Central Interior, but
there is a better chance of showers and thunderstorms in the
Middle Tanana Valley this afternoon and evening. Scattered
thunderstorms expected in the Eastern Interior again today after
thunderstorms produced well over 500 lightning strikes in the
Northeast Interior yesterday. High pressure remains over the
Beaufort Sea with troughing over the Western Arctic. A low will
move to Kodiak Island this evening enhancing leeside troughing
north of the Alaska Range, while high pressure will push northwest
over Southcentral Alaska. More scattered Thunderstorms Thursday
in the Upper Yukon Flats, with isolated thunderstorms for the
remainder of the interior.

Models...22/00Z solutions initialized well against the 22/06Z
surface analysis. The solutions handled the convective event in
the Eastern Interior well yesterday, and show a repeat for today.
Good agreement continues between solutions through about 60 hours
before they diverge over the Southwest Interior and Southcentral
Alaska. Surface to 500 hpa Cape Values in excess of 500 J/kg
today east of a line from Arctic Village to Beaver to the AlCan
Highway Border Crossing, along with negative Lifted Indicies
indicating very good thunderstorm potential. Will use an equal
blend for the precipitation, and lean toward the NAMDNG for
winds this forecast cycle.

Aloft...At 500 hpa...567 dam high that was over the Eastern
Beaufort Sea has moved to just south of MacKenzie Bay with ridging
extending north over 135W, and west over the Interior with 555 dam
heights over the Eastern Nulato Hills today. A 548 dam low that
was over Nulato yesterday is over Cape Lisburne this morning and
will move northeast to the High Arctic by Thursday afternoon. A
530 dam low 300 nm south of Sand Point will move to 150 nm east of
Sand Point this afternoon, then over Chignik by Thursday morning
at 539 dam. The low will move over King Salmon by Thursday
afternoon at 546 dam, and over McGrath at 551 dam Friday morning.
A 539 dam low 300 nm west of Wrangel Island will move east to
Wrangel Island by Thursday morning at 538 dam, and to Point Lay by
Friday morning at 539 dam. At 850 hpa...0C isotherm lies from
Kodiak Island to Wales then north this morning. The 0C isotherm
will be pushed west to lie over the Western Capes and the
Northwest Arctic Coast by Thursday morning. +10C isotherm
retreated back to the AlCan Border, but will push west over the
Central Interior today and tonight before retreating back to the
northeast Friday.

Surface...Thermal trough over the Northeast Interior today. Weak
high pressure west of Fairbanks to the Nulato hills, with weak
troughing over the West Coast. High pressure remains over the
Eastern Beaufort Sea, while troughing has developed over the
Western Arctic. A low in the North Pacific will move to Kodiak
King Salmon tonight with leeside troughing developing north of the
Alaska Range. A weather front will move across the Alaska Range
tonight. The Thermal trough will reorient to lie east to west
across the Interior Thursday north of Fairbanks.

Arctic Coast and Brooks Range...Stratus, fog, flurries,
sprinkles, northeast winds, spring in the Arctic continues. There
is a little break in a few locations this morning, but expect the
low stratus to move back in as the winds swing back around to
northeast and east. The Brooks Range will be partly to mostly
cloudy with a chance of Thunderstorms and showers east of the
Dalton Highway this afternoon and evening. A Not much change in
temperatures until Friday.

West Coast and Western Interior...Generally quiet, but a low
moving north in the Pacific will bring increased chances of
showers to the Lower Yukon Delta tonight and Thursday, and the
remainder of the West Coast Thursday night and Friday. Winds
generally light and variable. Temperatures slightly warmer.

Central and Eastern Interior...Another beautiful day at hand with
highs in the 60s and 70s. Most thunderstorms this afternoon and
evening will be northeast of Fairbanks but will not be surprised
if we get a couple lightning strikes to the west. Potential for a
significant amount of lightning today east of a line from Arctic
Village to Beaver to the AlCan Highway Border Crossing. Generally
light and variable winds, but with leeside trough redeveloping
expect some gusty winds to 20 mph today and 25 to 35 mph Thursday.
Temperatures warming slightly.

&&

Fire Weather...Near Red Flag conditions for much of the Interior
today as temperatures rise into the 70s, and Relative Humidity
Values fall into the lower 20s. Winds generally less than 10 mph
except around thunderstorms. Thunderstorms will be wet with small
hail. Heaviest thunderstorm activity will be east of a line from
Arctic Village to Beaver to the AlCan Highway Border Crossing.
Precipitable water values remain around 0.5 inch. Convective
Indicies look good with Lifted Index of around -3, and Cape Values
in excess of 500 j/Kg. Thursday looks similar to today, so expect
another round thunderstorms with a significant amount lightning.

&&

Hydrology...Koyukuk River levels running high and forecast brings
them up at Allakaket and Hughes, so Flood Warning continues for
those communities. Above normal snowfall this winter is
contributing to the excessive runoff that has the Koyukuk River
rising. Porcupine river running high, but levels continue to fall.
Yukon River breakup continues with no new information, caution
should be used near the river until it clears.

&&

Extended forecast for days 4 to 7...Not expecting any significant
change in the pattern. Expect isolated afternoon showers and
Thunderstorms for most areas. A low will move across the Arctic
Friday and Saturday bringing a change in wind direction, some
cooler temperatures, and a respite from the low stratus and fog
for a day or two. Gap winds in the Alaska Range Saturday into
Sunday. A low will move into the northeast Bering Sea spreading
showers north up the coast Saturday.

&&

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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Flood Warning for AKZ219.

&&

SDB MAY 19