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000
FXAK68 PAFC 151332
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
532 AM AKDT Fri Jun 15 2018

.ANALYSIS AND UPPER LEVELS...

Convection developed yesterday over the far northern Susitna
Valley and Copper River Basin in response to the southern edge of
a shortwave trough digging southward over northern Alaska.
For most everywhere else in mainland Alaska, the last of the warm,
beautiful sunny days this week was enjoyed yesterday. Already on
satellite, thickening cloud cover is moving northward into
southern Alaska, with radar returns indicating the leading edge of
the first in a series of moisture-laden waves already lighting up
over the central Alaska Peninsula near Port Heiden and Pilot
Point. This first wave of precipitation is the northern edge of a
large area of low pressure centered well south of Dutch Harbor.
The low is moving northbound towards the Aleutians and will be the
focus of the forecast for the next couple days. More on the low
below.

In the upper levels, ridging continues to build northward over
most of southern mainland Alaska while the previously mentioned
low becomes vertically stacked as a closed low south of the
Aleutians. The net result once again will be a wetter pattern as
the upper level flow strengthens and becomes more wavy in nature
with all of these features moving through the flow. Each upper
level wave will support the precipitation expected with broad
south to southwest flow helping transport plentiful moisture into
Southern Alaska.

&&

.MODEL DISCUSSION...

The models remain in very good agreement. As such there are no
model preferences this morning. The model consensus has also
become consistent in terms of timing the onset of precipitation on
Friday, so few changes were needed to the forecast.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The moisture laden front over the Gulf will surge northward today
into the Southcentral mainland. This will spread rain across the
the area from south to north today. The front will produce gusty
winds through Turnagain Arm, the Knik River Valley, and the Copper
River valley. These winds will, however not produce much
downsloping drying as the deep and moist southwesterly flow aloft
will overcome any potential drying. The front will move north and
east of the area late tonight, with the rain tapering off to
showers. The flow aloft will remain southerly and fairly strong,
as the main upper low works its way into the Bering Sea.

&&

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

Today, an occluded low in the North Pacific will move north
across the Aleutians and AKPEN bringing increased cloud coverage
and rain to the region. On the King Salmon radar (PAKC) has
detected a band of rain south of Levelock and Dillingham. The
moisture will slowly push northward. Saturday and Sunday are
looking wet and dreary. Once the surface low moves into the
eastern Bering, it will stall out.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
The high pressure that has been dominating the Bering is now over
St. Lawrence Island. The North Pacific low continues its trek
towards the Aleutians. The latest ASCAT/advanced scatterometer
pass has detected gale force winds south of the chain this
morning. Widespread prefrontal precipitation expected today for
the central and Eastern Aleutians. The surface low will cross the
chain near Unalaska Saturday afternoon. Expect cyclonic flow over
much of the Bering this weekend. Anticipate cloudy skies and
stratiform precipitation over most of the region through the
weekend.

&&

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

A major shift in the pattern will be well underway by Sunday
evening as a large trough will be in place over the eastern Bering
Sea with a big ridge over the Eastern Pacific. Folks who read this
forecast discussion tend to know what that means: it is gonna be
cloudier and wetter. Sunday night and Monday looks quite wet as a
low moving in from the subtropics brings widespread rain and
possibly some gusty southeast gap winds. Another low looks to move
inland Tue-Wed, but timing is uncertain at this juncture.
Thereafter, the trough weakens but it does look to remain in place
which should keep at least a decent amount of clouds and rain
chances through the end of the week...along with cooler temps.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...GALE 119 130 131.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
LONG TERM...JA