Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 181241
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
441 AM AKDT Tue Jun 18 2019

.ANALYSIS AND UPPER LEVELS...

A broad area of low pressure in the Gulf of Alaska continues to
be the prevailing feature. However, the jet stream on the south
side of the low looks to be a harbinger of change, as it is
starting to slide the low center to the east. Meanwhile, an
Arctic low is descending down the the west coast and should park
over the southwest part of the state later today. This could make
for interesting day for convection. Otherwise, another easterly
wave is well seen on satellite starting to make its way through
southcentral AK.

&&

.MODEL DISCUSSION...

Models continue to generally agree on the pattern through the
short term. The pattern of easterly waves propagating around the low
pressure in the Gulf should be ending after today as the low
moves southeastward out of the Gulf and weak high pressure is
shown building over southcentral Alaska on all models. This agreement
in the latest model runs leads to high forecast confidence.

&&

.AVIATION...
PANC...VFR conditions will persist. Turnagain winds are expected
to diminish early this morning and leave winds light and variable
for the remainder of the TAF period.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The generally northeast flow aloft remains over the region today
due to the presence of an upper level low in the Gulf of Alaska.
An easterly wave is embedded in this flow over the Copper River
Basin bringing in some showers. This wave will make it into the
eastern Susitna Valley and bring some showers as far south as the
Kenai Peninsula. However, it will stop moving westward and weaken
today as the low in the Gulf pulls southeastward. This will cause
the flow aloft to become more northerly over the Copper River
Basin and become light over the rest of Southcentral. This area of
weak flow aloft will be the area where a ridge will begin to
build over the area on Tuesday night and persist through Thursday.

This ridge will be strong enough to bring some clearing, but not
strong enough to put a good cap on the instability over the
entire area. Therefore there will still be some showers over
mountains in the afternoons and evenings and the Copper River
Basin may see a few thunderstorms Wednesday and Thursday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
The low over southwest Alaska will slowly track southwest through
the evening before finally stalling near the Kuskokwim Delta
coast. This disturbance will bring another round of thunderstorms
to much of southwest Alaska through this afternoon with the
highest chances around the middle Kuskokwim Valley. The
thunderstorms and showers will diminish overnight tonight. The
low will then linger near the coast through Thursday bringing
light showers to the area, primarily in the mountains.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
Ridging over the western Bering will work to stall a front
approaching the area from making it much farther east than the
western Aleutians. It will bring some rain to the islands this
afternoon before weakening and stalling from the ridge. The
benign pattern will hold through Wednesday before the ridge
finally pushes east on Thursday. This transition will allow for a
new system to approach the western Aleutians Thursday night.

&&

.MARINE (Days 3 through 5)...

No major low pressure systems expected in the short term until
late this week, as a weaker system approaches Kodiak, and a
potential gale-force front over the Western Aleutians toward the
weekend. Across the eastern Bering Sea, a long period of light,
long duration/fetch westerly winds could produce some larger seas
than the wind speed would suggest.

&&

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

Beginning the extended period forecast Thursday evening, there
will be a ridge axis over the eastern portion of the mainland of
Alaska with a weak upper trough over the eastern Bering Sea. A
weak warm front/low will be moving into the Gulf of Alaska but
will then be shunted southward as it tries to drift north on
Friday and Friday night. All the numerical global models and
statistical MOS guidance paint a pretty picture if you like summer
weather in Southern Alaska. The first significant "warm-up" looks
to be on tap as Southern Alaska heads into the weekend and next
week as the storm track shifts to the western Bering Sea and some
form of upper ridging and/or northerly upper flow builds over the
region. What this means is temps will likely push up into the 70s
(maybe even some interior 80s) with afternoon thunderstorms. Real
summer looks to be finally coming to the Southern Mainland.

&&


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

&&

$$

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



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