Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 191459
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
352 AM AKDT Wed Jun 19 2019

.ANALYSIS AND UPPER LEVELS...

Broad low pressure that had been in the Gulf of Alaska for days
was finally swept to the east by the jet stream. In its place a
shortwave ridge has brought some calm weather to southcentral AK
and looks to be in place for a couple days. One final wave is
pushing through the southeast mainland, but it isn`t doing much
and will push out to sea this morning.

Out in the Bering, low clouds and fog have moved in with cooler
air behind the low that had been firing convection over southwest
AK the past couple of days. High pressure building into the
Bering Sea has aided development of the fog and stratus. Out at
the end of the Aleutian Chain a front extending south from eastern
Siberia is hung up and nearly stationary as it pushes against
high pressure over the Bering Sea.

&&

.MODEL DISCUSSION...

Models are in good agreement for the short term. They seem to have
locked on to the weather transition well and are consistently
depicting weak high pressure midweek followed by another low
moving into the Gulf of Alaska later in the week. Therefore,
forecast confidence is high in the short term.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

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

Clouds will give way to sunny breaks during the afternoon with
convective clouds expected to develop along the mountains. A weak
boundary stretching between low pressure over the Kuskokwim
Delta...to the southern Alcan border...will be the focus for
afternoon showers and thunderstorms along the Alaska Range as
disturbances move ahead of the Southwest low and another short
wave moving south from the interior. Otherwise...expect afternoon
sea breezes along coastal locations with relatively light winds
inland.

Early Thursday morning another slow pattern shift begins with low
pressure over the Southwest beginning to lift north as the next
low pressure moves up from the North Pacific. A stream of low
level moisture moves across the Gulf ahead of this next system
bringing low clouds across the Gulf of Alaska early Thursday with
fog possible across much of the western and central waters. For
inland locations...expect a persistent pattern with light winds and
diurnal showers along the mountains. The one difference for Thursday
will be that thunderstorms are possible further south along the
Talkeetna Mountains and Matanuska Valley as the thermal ridge shifts
south.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
The low over the southwest coast will track north through the
Kuskokwim Delta today bringing light showers as it passes. The
showers will diminish tonight and then benign weather will linger
through Thursday. On Friday shower activity will pick up again
with the majority of the showers over the mountains.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
Ridging remains over the western Bering which has stalled an old
front over the western Aleutians. This setup will bring light rain
to the Aleutian Islands into Thursday when the ridging finally
pushes east. Additionally, on Thursday, a North Pacific system will
approach the Alaska Peninsula bringing rain to the area Thursday
night. A second system is approaching the western Aleutians behind
the ridge and will make it to the Aleutian Islands early on Friday
as it tracks to the northeast.

&&

.MARINE (Days 3 through 5)...

On Friday, a low traversing the Gulf of Alaska will spread an
easterly front (well below gale force) up to about Kodiak before
the low weakens and moves east Friday night, leaving in its wake
high pressure through Sunday, keeping the region free of any
strong storms or gale force winds.

The storm track during this period will shift over to the western
Bering Sea and Western Aleutians Friday night as a near gale force
low moves into that area. There is high confidence that this low
weakens through Monday and remains west of the Pribilof Islands,
keeping quieter weather and typical fog/stratus over the eastern
Bering Sea.

&&

.LONG TERM FORECAST (Days 4 through 7)...

Beginning the extended period forecast on Friday evening, there
will be a low tracking over the Gulf of Alaska moving east with a
second low moving into the Southwest Bering Sea. Upper ridging,
which is typical this time of year, will be building into the
eastern portion of Alaska from the Yukon. The vagaries of the
pattern still remain uncertain, but not much has changed from
yesterday, with the expectation that the Gulf low will move east,
allowing for the ridge to amplify inland with warming temps and
the threat for interior thunderstorms through the weekend. By
Sunday and Monday, all the global numerical models still simulate
a strengthening high which, should it occur, result in the
warmest temps of the year for parts of the Southern Mainland as
850 hpa temps rise above 10C, in conjunction with "offshore" flow.
Some interior locations may hit the 80s. The overall pattern of
offshore flow is not strong, however, so temps will be moderated
some by afternoon thunderstorm developments and sea breezes across
coastal regions. Uncertainty builds late Tue as the models shift
where the upper ridge builds, but overall, the "summery" pattern
will likely persists in some fashion, with threats for
thunderstorms and warmer than average temps.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BJB
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
MARINE/LONG TERM...JA


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