Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 311154
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
354 AM AKDT WED AUG 31 2016

.ANALYSIS AND UPPER LEVELS...

The upper level pattern persists this morning with a blocking
ridge centered over the Bering Strait and low pressure centers
spinning over the eastern Gulf of Alaska and the western Bering.
Low pressure over the Bering has two embedded low centers, one
over the central Aleutians and a second core diving south from the
Kamchatka Peninsula. At the surface, winds are tapering down
across Southcentral as the pressure gradient relaxes with the
surface ridge shifting inland along the southwest coast. To the
west, an occluded front continues to slowly progress north and
east across the Bering.

&&

.MODEL DISCUSSION...

Models continue in good synoptic agreement through Thursday;
therefore, only minor changes were made in the morning package
using the NAM. On Thursday, models begin to differ in strength
and track of the Bering low as it begins to track east. The GFS
was used for it`s middle ground solution which slowly tracks the
surface low across the central Aleutians into the southern Bering
late Friday night.

&&

.AVIATION...
PANC...VFR conditions and light winds will prevail through the
next TAF package as ridging persists over the southern mainland.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
High pressure will remain over south central Alaska through
Thursday night. The flow aloft will gradually shift from northeast
to northwest as the high center retreats westward into northeast
Russia. Offshore winds in coastal areas will increase a bit today,
then slacken off again tonight. Warm daytime temperatures will
continue, with some daily records likely to fall again today and
Thursday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A strong upper level ridge will shift slightly eastward and begin
to slowly elongate over the Southwest Mainland through Thursday,
keeping warm and dry weather over the region. Weak inland winds
and continued stable conditions over the area will allow for the
development of more valley and lake fog during the overnight and
early morning hours through Friday, especially across interior
portions of the Lower Kuskokwim Valley and Bristol Bay.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A North Pacific low and associated warm front will continue to
lift northward through much of the Aleutian chain and the
Western/Central Bering today. As the low reaches it`s maximum
intensity, this system will spread rain and gusty southeast winds
across the entire Aleutian chain/Pribilof Islands by this
afternoon. The low will then weaken and occlude Thursday, with
periodic rain lingering over most of the Bering Sea. A new low
will develop off the aforementioned North Pacific low Thursday,
and track northward toward the Western Aleutians by Friday
morning. This will continue the wet and gusty conditions over
much of the Bering and Aleutian through the end of the week.

&&

.LONG TERM FORECAST (Days 3 through 7)...

A little bit has changed in the extended forecast over the past
couple of models runs. The area of low pressure south of the
Central Aleutians will push a front through the southern Bering
Sea and northern Pacific on Friday. However, it`s looking more
probable that a triple point low develops south of the Alaska
Peninsula Friday afternoon and should slow the momentum of the
front as it approaches the Alaska coastline. This has led to a 12
to 18 hour delay for when the frontal boundary was supposed to
begin moving inland. This will bring the first chances of rainfall
to Southwest Alaska Friday afternoon/evening instead of late
Thursday. This front, as expected before, will continue to push
eastward toward Southcentral Alaska and increase rain chances by
Sunday. The front will fall apart quickly once inland so it is
quite difficult to judge the likelihood of rainfall at this time.
It should be noted that as the upper level ridge continues to
erode that a return of some southwesterly flow aloft is likely.
However, it will not be nearly as steep as before therefor no
significant moisture plume is expected to advect northward toward
the state.

Models are still in overall remarkable agreement through early
next week with the main synoptic features but do struggle with a
few shortwaves in the arctic. Low pressure looks to encompass much
of the state by midweek next week with a showery regime returning
to the state. However, the extent and coverage of these showers
will depend greatly on an arctic trough that enters the state on
Tuesday.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...MC



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