Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 160123
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
523 PM AKDT Sat Jun 15 2019

.ANALYSIS AND UPPER LEVELS...

There is no significant change from the pattern yesterday save
from the progression of the significant features rotating around
the parent upper-level low south of the AKPEN.

Aloft, the upper-level low is keeping the main storm track south
of 50N, but the north side of this circulation is pulling in a
 northerly draw off the North Pole into the Eastern Bering. A
northeast to southwesterly-oriented jet max is blowing out of
Bristol Bay to the Central Aleutians around 90-100 knots and
wrapping into this parent low.

At the surface, the occluded front is stretched from the Southern
Bering into the central Gulf of Alaska and is dissipating with
the parent surface low holding near 165W. Another surface low in
the central Gulf is focusing a southern draw of warmer, wetter air
mainly over the eastern Gulf with the northern fringe working into
Prince William Sound bringing widespread light rain. A stationary
boundary was located just north of Alaska Range and held back a
moderating Arctic airmass. This boundary was creating plentiful
cloud cover over Southwest AK and fog near Broad Pass this morning.
Fog was also noted near Kenai. Kodiak continued with the low,
sloppy weather from yesterday. Conditions remained low in the
Eastern Chain into the AKPEN as well. And wildfire smoke from the
Kenai Peninsula was visible in FAA webcams over Anchorage.

&&

.MODEL DISCUSSION...

Models were in fair agreement through Monday. By Tuesday, timing
and location of pressure centers were slipping, along with the
placement of the thermal trough over the Interior. High resolution
wind models have been having difficulty with the placement and
timing of the Turnagain Arm wind this weekend and this continues
today.

A new forecast challenge emerged overnight and continues with the
latest model runs: the main models were all reasonably consistent
in bringing in an Eastern wave across the ALCAN border Monday-
Tuesday and rotating that into Southcentral Alaska.

&&

.AVIATION...
PANC...
The Turnagain Arm wind may make a brief appearance this evening
after 00z Sunday then diminish just as quickly around 06z. One
concern is the potential for LLWS with light surface winds while
Southeasterlies ride over this layer at 25-35kts. VFR flying is
expected through the period with passing light rain in the
vicinity.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3,
Saturday night through Tuesday afternoon)...

A weather front over the north Gulf Coast weakens in place tonight.
A secondary low heads north and to south of Kodiak Island Sunday
night then drifts east on Monday night and Tuesday. Its associated
front moves across the Barren Islands and north Gulf Sunday
night/Monday morning then falls apart along the coast Monday
afternoon. The resultant weather will be generally cloudy with
periods of rain along the coasts with the frontal activity through
Monday then transition to more showery weather as the front
weakens on Tuesday. Inland areas also will be on the cloudy side,
but with some cloud breaks and showers through Tuesday. That said,
the increased easterly flow aloft could open up Southcentral to
weaken easterly waves which would enhance precipitation potential
Monday/Tuesday. For now though will keep conditions on the
showery side.

Increasing pressure gradients will give rise to brisk easterly
winds across Turnagain Arm, southeast out of the Knik River
Valley, and southerly along the Copper River this afternoon and
evening. Sunday will bring weaker versions of the same flow and
Monday wind regimes will be dominated by seabreezes.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
South flow ahead of a vertically stacked low south of the eastern
Aleutians is keeping cloudy skies over Southwest, thus surface
temperatures have been slow to warm this afternoon. Scattered
showers continue over the southwest mainland, though areas to the
lee of the Aleutian Mountains and Kilbuck Mountains are getting
downsloped thus reading slightly warmer temperatures than
elsewhere in Southwest. While an isolated thunderstorm or three
can`t be ruled out this evening, we`ll really need some sun to
poke through to realize instability.

As the steering low south of the eastern Aleutians continues to
fill Sunday, a triple point low will rotate around its base
towards the Gulf. Southerly flow with widespread cloud cover and
scattered showers will persist in the greater Bristol Bay area,
save for a downslope hole on the north side of the AKPEN. Warmer
north flow will develop in the Kuskokwim Valley, thus there will
be a slight chance of thunderstorms Sunday evening. Expect patchy
smoke from area wildfires at the surface as well.

An upper low will dive down towards the Interior from the North
Slope Monday. This will enhance north flow from the surface to
upper levels, and as a result Monday will be several degrees
warmer than Sunday, especially in the Kuskokwim Delta. The
combination of these features will enhance convection over the
lower Kuskokwim Valley, Kuskokwim Delta, and Kilbuck/Wood-Tikchik
Mountains Monday evening.

Expect a general cooling trend Tuesday over Monday in a transition
to onshore flow.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A closed low south of the eastern Aleutians will slowly fill and
drift eastward Sunday into Monday. While precipitation is possible
in the periphery of this low, expect generally quiet conditions
over most of the Bering and Aleutians over the next several days.
North flow will prevail over the Bering, with persistent cloudy
skies.

&&

.MARINE (Days 3 through 5)...
Confidence is very high that there will be no gale force winds
from Tuesday through Thursday. It is indeed likely that winds and
seas will remain below Small Craft Advisory criteria.

&&

.LONG TERM FORECAST (Days 4 through 7)...
The forecast period begins on Wednesday with a weak upper low
over western Alaska, and a weak upper high over the southern
mainland. Another weak upper low will be sitting over the western
Bering Sea. This pattern is expected to change very little. With
very weak flow aloft and in the lower levels, a relatively quiet
weather pattern is expected for the middle and later portions of
next week, with no significant events on the horizon. Temperatures
will generally be above normal, with some showers possible.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MM
MARINE/LONG TERM...BL



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