Small Craft Advisory 73, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
116 PM AKDT Sat Aug 29 2020

.SYNOPSIS...
A shift in the pattern is underway as the Mainland transitions
away from the persistent "easterly flow" pattern aloft to a more
fall-like pattern as a storm moves into the Bering Sea and inland
south of the Alaska Range. This will bring in more stable air,
will end thunderstorm threats after today, and bring in gradually
cooler weather conditions.

&&

.DISCUSSION...

Upper Levels and Analysis...
The merger of three easterly waves has resulted in a remnant broad
upper low centered over the Lower Yukon Valley. Weak troughing
persists over the North Slope with a weakening persistent high
pressure ridge over and north of Wrangel Island. The big story is
to the southwest over the Aleutians/North Pacific where a very
strong upper trough is in place. Undercutting this trough is a
remnant of the once Typhoon Bavi, and this subtropical moisture
stream can be seen on satellite as a massive shield of high
cirrus, otherwise known as a "baroclinic leaf". This storm will
plow through Bristol Bay tomorrow and bring strong winds to the
Alaska Range passes.

Central and Eastern Interior...
An isolated thunderstorm threat will exist through early evening
south of the Yukon Flats to the Alaska Range as the upper level
flow becomes more southerly. One more night of widespread
overnight valley fog is in store for us given partly clearing
skies and weak pressure gradient once again tonight. A front
moving to the southern part of the Alaska Range will rapidly
increase the pressure gradient and southerly winds this evening
through the AK Range passes, with a reinforcing surge of chinook
winds coming Sunday evening through the overnight. This will push
50-65 MPH winds through the passes, with strong winds into the
40+ MPH range moving into Delta Junction. The front will move
north of the AK Range Sunday night, bringing rain as the front
moves northward. Areas closer to the AK Range will see a downslope
shadow and may only see a brief shot of light rain. Thereafter,
the low falls apart and weakens, with weakening Alaska Range winds
and leftover clouds and intermittent rain lasting through
Tuesday.

West Coast and Western Interior...
Showers and possibly an isolated interior thunderstorm will push
offshore tonight with a brief drying trend as a front to the south
stalls and weakens. This will increase the northeasterly offshore
pressure gradient with winds becoming quite strong Sunday as gale
force winds are expected over parts of the open Bering Strait
waters and along the capes. The next front will move into the
Lower Yukon Sunday afternoon and overnight, bringing rain to that
area, along with some showers as far north as Norton Sound.
Showers persist through Tuesday as the low slowly moves inland and
weakens. Expect continued blustery conditions along the coast as
the broad cyclonic flow continues and winds turn more northerly.

North Slope and Brooks Range...
Easterly winds will increase as a storm moves inland through
Bristol Bay. Otherwise, no major changes in sensible weather as
periods of very low stratus and fog persist. Some periodic drizzle
is also possible along the coast. Increasing southerly winds aloft
will also support periodic showers along the Brooks Range and
plains north of the range.

Coastal Hazard Potential Days 3 and 4...
High surf is expected along the north side of St Lawrence Island,
east of Gambell, as strong northeast to north winds develop today
through Sunday and continue into Tuesday. Water may also be
backed up into Kotlik as the winds hold water in the Kotlik river.

&&

.FIRE WEATHER...
Today will be the last day in the near future for threats of
Interior isolated thunderstorms as the pattern switches to an
offshore flow with increasing northeast winds, with the exception
of 40-65 MPH winds in the Alaska Range tonight through Sunday
night. Rain moves into the Interior Sunday night and Monday with
clouds and showers persisting into midweek.

&&

.HYDROLOGY...
No major concerns.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Wind Advisory for AKZ225-AKZ226.

Small Craft Advisory for PKZ200-PKZ220-PKZ230-PKZ240-PKZ245.

Gale Warning for PKZ210-PKZ225.

&&

AHSENMACHER AUG 20