Area Forecast Discussion
Issued by NWS Anchorage, AK

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337
FXAK68 PAFC 131240
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
440 AM AKDT Wed Jun 13 2018

.ANALYSIS AND UPPER LEVELS...
Fairly quiet conditions are seen across most of the region this
morning as a weakening Arctic trough slowly progress eastward
across the Copper River Basin and towards Southeast Alaska. Mid
and upper level clouds can been seen advecting south into
Southcentral from the parent low currently situated well to the
north over the Arctic Sea, but dry northerly flow across most of
the state is leading to little to no precipitation. Out west, a
large area of high pressure extends from Eastern Russia all the
way across most of Western Alaska, even trying to nudge some into
Southcentral. This is leading to clear skies and dry northerly
winds over Southwest this morning. Strong subsidence underneath
the high is leading to persistent widespread low stratus and fog
over the Western half of the Bering and extending across the
Aleutians. Visible satellite imagery this morning shows the
Eastern half of the Bering cloud free as the dry northerly winds
coming off the mainland is keeping the stratus at bay.

&&

.MODEL DISCUSSION...
Models are all in good agreement this morning with the synoptic
level pattern, including locking in on the placement and
intensity of the North Pacific low moving towards the Central and
Eastern Aleutians on Thursday. There are some slight timing
differences in the leading front as it pushes north into
Southcentral Friday morning, but these should be worked out in the
next day or so.

&&

.AVIATION...
PANC...VFR conditions with light winds will persist through the
TAF period.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

An upper trough over the Copper River Basin will be the focal
point for showers today, though there could be a few develop over
the Susitna Valley along the Talkeetna Mountains. A weak trough
sweeping down from the north on Thursday will likely kick off
showers across Southcentral with the focus along the mountains.
As the thermal trough intensifies and stability indices approach
critical thresholds, the added lift with the trough may kick off
some isolated thunderstorms Thursday afternoon and evening over
the Copper River Basin.

Gusty outflow conditions over the eastern Kenai Peninsula and
Prince William Sound should diminish the afternoon. Otherwise,
seabreezes will be the general rule into Thursday. A front heading
north late Thursday will bring rain to Kodiak Thursday night and
signal a change to a wetter pattern to much of Southcentral.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

The longwave pattern features high pressure over the Bering and an
upper low over the Beaufort Sea and North Slope with the trough
axis extending into Southwest Alaska. Expect dry and stable
weather the next two days. On Thursday, a mature low in the North
Pacific will move north along the eastern Aleutians and AKPEN
bringing increased cloud coverage and rain to the region late
Thursday through Friday. Gusty easterly winds are also possible as
the pressure gradient from this system enters the region,
especially in gap locations east of the Alaska Range.

&&

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

A dome of high pressure continues to dominate the Bering. Low
stratus and patchy fog will persist.  By Thursday, a developing
low will advance toward the Aleutians. This system will rapidly
intensify as it heads north. Gale force winds and rough seas will
accompany this system. The surface low will make its first
landfall in the Central Aleutians near Unalaska early Saturday.

&&

.LONG TERM FORECAST (Days 3 through 7..Fri through Tue)...
Besides some convection and a strong Arctic trough over last
weekend, June has started out very Summer-like across much of
Southern AK. But things are about to take a turn to a much
cloudier, rainy, and slightly cooler set-up. The well-advertised
front will make its way into AK from the North Pacific on Fri.
This front will have pack a little extra "punch" as it wraps in
some extra-tropical remnants of a former tropical storm. So expect
very wet conditions along the Gulf Coast late Fri and continuing
into Sat. It will also bring a healthy amount of QPF to SW AK as
the front slings through there. Places in the lee of the Kenai and
Chugach Mountains will see somewhat reduced precipitation values
with some downsloping, but they will also see some impressive
channeled winds. From the Barren Islands, to the Turnagain Arm,
the Knik River Valley, and the Copper River Basin, gusty
southeasterly winds are in store.

This system will reorient the entire longwave pattern. A broad
trough will become well established over the Eastern Bering. This
sets the entire southern portion of the state up with moist,
southerly flow. While this certainly doesn`t mean continuous rain
for the area, it will spell a marked increase in cloud cover.
Then, as waves of energy pinwheel through the base of the trough
and move south to north towards southern AK, each will have the
potential to bring steady rain. This will be especially true for
the Gulf Coast (Prince William Sound, Cordova, etc.). This pattern
really looks to hold on through much of next week (June 18-22).
Overall, fire weather concerns will be relatively low during this
time.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales 155 172 174 176.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KVP
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PS
LONG TERM...MO



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