Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 231255
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 AM AKDT Tue May 23 2017

.ANALYSIS AND UPPER LEVELS...
A frontal boundary and low continue to track towards Southcentral
Alaska. The Kenai radar is in the lull before the storm and
presently pretty uneventful. On satellite as of 12Z or 4 AM the
leading edge of the front is entering the AK Peninsula. The jet
core is near the Pribilof Islands and handedly over 130 knots.

&&

.MODEL DISCUSSION...

The NAM...ECMWF and the GFS are in lock step regarding the 500 mb
heights and the surface features at MSL. Sensible weather-
wise...the model consensus is very good pinging into the QPF...the
gusty winds and the temperatures in the pre and post frontal
environment. Wednesday`s event in the Anchorage metro area is a
high confidence event.

&&

.AVIATION...
PANC...Gusty Southeast winds are expected across the airport
complex through late this evening. As the next frontal boundary
pushes inland...expect the cigs to drop. At this time...expect
the light rains to commence at PANC at 12z Wednesday. Although
TAF updates expected as the latest model data becomes availble.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A bout of rain and wind will afflict the Cook Inlet region as a
very fall-like pattern sets up aloft. A weak trough will pass
today which could trigger some afternoon showers over the Chugach,
Talkeetnas and Wrangells. The developing westerly flow will keep
most activity around the Copper River Basin. Some clearing and
light winds should make for a pretty decent spring day for most of
southern Alaska.

However, that is literally the calm before the storm. A beefy
120 kt jet aloft will punch overhead tonight into Wednesday
bringing a lot of moisture with it. Rain will overspread the area
from southwest to northeast late tonight, increasing gap winds as
it does so. It looks to be a semi-rare occurrence where we get
rain and wind at the same time in the Anchorage area. Wednesday
will be pretty wet until the evening hours when both the wind and
rain should taper off. A colder air mass will be left in the wake
of this system, leaving below normal temperatures.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
An incoming frontal system and increasing southwesterly flow aloft
will bring rather wet and breezy conditions to Southwest Alaska
this evening through Wednesday morning. The frontal system will
begin spreading precipitation across the Greater Bristol Bay area
this afternoon. Rain will increase in intensity this evening with
moderate to heavy at times rainfall spreading inland overnight.
Cold air aloft behind the frontal system will spread inland
Wednesday afternoon through Wednesday night. This cold air aloft
will bring the potential for isolated thunderstorms both Wednesday
and Thursday afternoon and evening as well as rain showers
transitioning over to snow showers Wednesday night.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The large vertically stacked low will track into the northern
Bering this afternoon with an upper trough to its south swinging
east from the western Aleutians this morning through the central
Aleutians this afternoon and evening and into the eastern Bering
tonight through Wednesday. The cold upper trough will swing inland
into Southwest Alaska Wednesday night and Thursday to be followed
by broad zonal flow across the Bering and another low pressure
system tracking east down the length of the Aleutians Wednesday
night through Thursday night.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The mid to long term forecast starting Wednesday evening seems to
be that of a tale of non summer like weather. The current model
depiction is that Alaska will be stuck in troughing pattern where
the weather will be active through the weekend. Unfortunately,
this is a dramatic flip from guidance just a few days ago. The
first system will be exiting south central as we move into
Wednesday night. Weak low pressure will hang around the Gulf
through the end of the week, leaving coastal and upslope regions
moist. By Saturday afternoon the next front moves past Kodiak and
brings another round of unsettled weather through Monday.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 155 172 174.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...ML
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...SS



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