Gale Warning 378, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
330 PM AKDT Wed Aug 21 2019

.ANALYSIS AND UPPER LEVELS...
The upper level pattern shows the trough persisting along the
AlCan border. The low near the Central Aleutians is now beginning
to get entrained into that AlCan trough in the broad flow which
will help move it eastward. The jet stream continues to run south
of the Aleutian low and through then Central Gulf of Alaska
before curving southeast toward Washington State.

&&

.MODEL DISCUSSION...
Models remain in very good agreement through the weekend. They
also show remarkable run-to-run consistency with the development
of a series of triple-Point lows tracking south of the Aleutians
and into the southern Gulf of Alaska. Once again, the main issue
will be the small scale effects that will drive local winds around
the fires and the smoke.

&&

.AVIATION...
PANC...Smoke will continue to be around the airport through the
TAF period. Southeast winds through Turnagain Arm will increase
this evening but there is a bit of uncertainty as to whether they
will curve enough to move over the airport. At this time it looks
like the strongest of these winds will remain over the water and
could even cause periods of northwest winds due to an eddy effect
off the wind core. It remains to be seen whether these winds will
help or harm the smoke situation as they have to potential to
bring in more clear air from Prince William Sound or to increase
the smoke off the Swan Lake fire. Small differences in wind speed
and direction may cause very different results.

&&

.FIRE WEATHER...
For fire weather, the biggest question is how the strong the
southeast winds will be over the Swan Lake fire tonight through
tomorrow. Other fires in the region are not as susceptible to the
southeast direction as Swan Lake, including the ones in the
Bristol Bay region. Overall there will be a slow trend toward more
moist conditions into the weekend. Smoke is expected to remain an
issue across Southcentral and parts of Southwest Alaska for the
next few days.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
Weak ridging is in place over Southcentral Alaska. There are
several wildfires in the state of Alaska and the particulate
matter from these fires has been trapped in the boundary layer.
Some of the local observation sites are reporting haze (HZ) while
other are reporting smoke (FU). A Dense Smoke Advisory is in
effect for the Interior Kenai Peninsula south to Seward. Light
winds and stable conditions will keep smoked from the Swan Lake
Fire trapped near the surface.

An organized front is on track to move into the Gulf Of Alaska
this forecast period. The lion's share of the moisture will remain
over the Gulf Of Alaska. Kodiak and Prince William Sound can also
anticipate rain from this system but the mountains will prevent
the moisture from making any headway into Anchorage or the Mat-
Su Valleys. Friday the arctic trough will descend south of the
Brooks Range and later south of the Alaska Range. This trough will
usher cooler temperatures aloft into the region and increase the
chance of showers.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Southwest Alaska will continue to see quiet conditions and
relatively clear skies through this evening. The active weather
will remain on the southern portion of the AKPEN as a front
associated with the triple point low moves eastward towards the
Gulf. A chance for precipitation returns mainly along the Alaska
Range on Thursday as a trough pushes into the southwest, impacting
the mainland. As the trough and associated shortwave continue to
move southward on Friday, a chance for convective activity and wet
isolated thunderstorm make their return to the Southwest. The
best chance for these wet thunderstorms will be along the Alaska
Range, Kuskokwim Valley, and interior Bristol Bay.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Small craft advisory winds remain over the western Aleutians and
Bering through the evening hours. A front associated with a triple
point low will be the biggest impact to the southern side of the
eastern Aleutians and AKPEN over the next 24 hours. Winds will
continue to be small craft advisory level through Thursday
afternoon, but will likely increase to low end gale force winds
overnight tonight into the early morning hours. Once this system
moves out of the area, northerly flow will persist over much of
the Bering through the early weekend.

&&

.MARINE (Days 3 through 5: Saturday through Monday)...
Westerly flow is expected across the Gulf through the long term
period. There is moderate confidence that a low will develop over
or just offshore of the Alaska Peninsula Sunday. However there is
low confidence regarding the exact track and strength of this low
as it moves eastward into the Gulf for Monday. Meanwhile over the
Bering, there has been consistent indication that a ridge of high
pressure will persist through early next week.

&&

.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...
Unfortunately there continues to be only muddled signals in the
long-term weather pattern for next week. We have high confidence
that a longwave trough will be in place over the state with a
ridge of high pressure over the western Bering. Model solutions
continue to vastly disagree in the timing and strength of several
shortwaves that move across Southcentral early next week. This
translates into an unsettled, cloudy, and showery weather pattern
that will likely persist through the middle of next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Dense Smoke Advisory 121 125.
         Flood Advisory 121 125.
MARINE...Gale Warning 155.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...PJS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AH
MARINE/LONG TERM...KO