Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 270012
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
412 PM AKDT Wed Apr 26 2017

.ANALYSIS AND UPPER LEVELS...
The upper level pattern over the state consists of the large low
in the south-central Bering Sea and a ridge extending out of
Canada into the northern Interior. This is keeping south to
southeast flow over southern mainland Alaska with some short wave
embedded in the southeasterly flow over the Gulf of Alaska into
Southcentral.

&&

.MODEL DISCUSSION...
Models are still holding close together for the next few days with
no significant differences to discuss. As we get into the weekend,
there is a general breakdown in consistency between models in the
low complexes in both the Bering Sea and Gulf of Alaska. The
periods of light precipitation in Southcentral this weekend will
be dictated by weak upper level features which are not discernible
yet.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Weak cyclonic flow aloft combined with a weakly unstable airmass
will continue to produce isolated to scattered showers through
Thursday afternoon, primarily over the mountains and during the
afternoon and evening hours. A slightly more substantial short-
wave will lift northward across the Kenai Peninsula and on up to
the Susitna Valley Thursday night. With generally weak south to
southeast flow (very little in the way of downsloping) and an
increase in instability as upper level temps cool, it looks
favorable for some light rain from the Western Kenai Peninsula to
Anchorage and portions of the Mat-Su. A much larger more
significant upper trough will swing into the Gulf on Friday which
will produce increased showers over the Gulf while broad-scale
cyclonic flow over Southcentral will lead to mainly diurnal
showers, focused along the mountains once again.

Winds will generally remain on the light side. As the trough
swings into the Gulf on Friday a ridge will strengthen along the
north Gulf coast. This will lead to stronger sea breezes and more
notably, gusty afternoon and evening winds through Turnagain Arm
into part of Anchorage, along the Knik River Valley into Palmer,
and along the Copper River.

&&

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

Scattered rain showers are expected to continue through this
evening across Southwest Alaska as weak upper level disturbances
push through the area. Portions of the Kuskokwim Delta, mainly
from Bethel westwards, will likely see patchy fog develop
overnight with some clearing skies coupled with a moist and stable
airmass. Some locations could see visibilities as low as one half
of a mile at times but the nature of radiation fog makes it very
difficult to pinpoint where exactly the fog will be the thickest.
The rest of the week will see clearing skies which will allow
temperatures to warm a few degrees warmer than previous days.
Colder air aloft has filtered in across the region which has aided
in creating a conditionally unstable air mass. Scattered to
widespread rain showers will be possible, especially near the
mountains, Thursday and Friday but thunderstorm potential looks
rather unlikely with not enough instability or forcing available.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Isolated to scattered rain showers will continue across much of
the Bering Sea through Thursday with an upper level low near the
Central Aleutians slowly meandering eastward. Fog near the
Pribilof Islands should re-develop under a rather unstable air
mass but should finally mix out Thursday afternoon. All eyes then
turn to a frontal boundary pushing through the western half of
the Bering Sea late Thursday into Friday. This should help bring
back a nice swath of gale force winds along the frontal boundary
with periods of light to moderate rainfall. This front will move
to the Alaska Peninsula by late Friday night but will have
weakened substantially by the time it makes it that far east.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The long-term forecast looks like a continuation of the rather
cloudy pattern that has spread across much of mainland Alaska. The
main feature for the weekend and into mid next week is a low that
will be tracking through the Bering over the weekend and then move
across the Alaska Peninsula and eventually into the Gulf of Alaska
next week. There is good model agreement with this system through
the weekend giving higher confidence for showers across the
southern mainland and around the Bering for much of the long term.
Early next week areas along the north Gulf coast look to see more
steady rain as the low moves towards the Gulf.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales 177 178 411.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...SB/PS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DK


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