Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 221244
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 AM AKDT Sun Mar 22 2020

.ANALYSIS AND UPPER LEVELS...

A 1047 mb high remains in control from the Bering Sea/Aleutian
Islands eastward into Southcentral, and northward into the
northern parts of the state. Meanwhile, a a trough stretched from
the Yukon across the eastern Gulf, with a 1005 mb surface low that
was situated just offshore of the Panhandle, to the southwest of
Sitka.

&&

.MODEL DISCUSSION...

Overall the numerical models remain in decent agreement from
southwest Alaska and the Alaska Peninsula eastward. However,
there`s some model disagreement regarding a shortwave trough that
moves from the north Pacific into the west central bering. More
specifically, the models differ in the orientation of the heights
aloft, the surface low positioning and strength tied to said
trough, and any lead impulses ejecting ahead of it that ridge the
periphery of the ridge to its east. This results in some
questions being raised as to who gets the better chance of
precipitation, and how much, as either the trough or lead impulses
cross the region.

&&

.AVIATION...

PANC...Light winds will continue. Satellite imagery and area web
cams show some stratus lurking over some portions of town and
over the Cook Inlet. Additionally, a brief period of reduced
visibilities has already been observed. This will likely continue,
with brief periods of ceilings near 500 feet and visibilities in
the 1 to 3 mile range possible through this morning.

&&

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

The front that brought snow to SOuthcentral yesterday has moved
east of the area as high pressure builds in from the west. This
will increase the northerly flow and keep gusty winds through
channeled terrain, especially along the north Gulf coast. These
winds should be strongest today and then begin to diminish some
tomorrow.

Areas of fog have developed along Cook Inlet this morning with
densest areas near Kenai. With the increasing northerly winds
today this fog should dissipate after sunrise this morning.

A series of weak shortwaves will move across the northern
periphery of the ridge tonight into Tuesday. These waves will
increase cloud cover along the ALaska Range and may even bring
some snow to parts of the AK Range. However, the energy with these
waves will remain farther to the north keeping the remainder of
Southcentral dry.

&&

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

The strong upper level ridge of high pressure will continue to
build into Southwest Alaska today and remain over the region
through early Tuesday morning. As a result, quiet and dry weather
will be in control although there may be some areas of patchy fog
Monday morning in the Bristol Bay region.

A series of shortwave troughs are expected to ride up along the
backside of the ridge which will aid in breaking the ridge down
and pushing it off to the south and east. The first shortwave
trough is expected to begin affecting the Lower Kuskokwim Delta
region Tuesday morning with multiple shortwaves in the mean flow
continuing to impact the region through midweek. Due to this,
increased precipitation chances are expected with a mix of rain
and snow as the warm air aloft overruns the cold air at the
surface. Temperatures will be hovering in the 20s to 30s as these
waves of energy move through the area.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A strong upper level ridge of high pressure will remain in place
across much of the Bering through Sunday evening before shifting
off to the south and east. As a result, the prevailing weather
will continue with dry and quiet conditions.

A series of shortwave troughs riding up on the back side of this
ridge which will bring active weather back to the area. A front
associated with a low pressure system currently over the North
Pacific will lift northward Sunday afternoon and evening bringing
rainy conditions to the central Aleutians as temperatures aloft
will be too warm for any frozen precipitation. As this front
continues to lift northward, the precipitation will spread into
the Bering Sea with the Pribilofs seeing the rain chances
increasing late Monday morning with the threat continuing through
Tuesday night. Along with this some low end gale force winds are
expected from Amchitka to Atka with a wide area of small craft
advisory winds over the southern Bering.

A weak upper-level high will build into the western Bering and
western Aleutians Wednesday bringing subsiding winds and lessening
precipitation as the aforementioned system pushes east.

&&

.MARINE (Days 3 through 5, Mon through Wed)...

In the Gulf, winds should not exceed small craft through Wednesday.
Due to slight differences in the models, low end Gales are possible
for the western Aleutians on Thursday with the rest of the Bering staying
at or below small craft criteria.

&&

.LONG TERM FORECAST (Days 3 through 7, Mon through Sat)...

Strong confidence remains that an upper level ridge will remain over
the southern part of Alaska through the middle of the week. Tuesday
morning, a North Pacific low will get caught up in the backside of
the ridge, which will bring it northwest across the western Aleutians
and into the Bering Sea. This low will weaken the ridge, thereby flattening
it, and looks to force the low southeastward across the eastern Aleutians
and right back into the North Pacific by Thursday. Following this, a
zonal flow aloft will be the dominant feature into Friday night. After
this, an area of low pressure is on track to enter the western Bering,
although, strength and timing remain the forecast challenges for this
feature. It is a possibility that this low will weaken into a trough
as it makes its way towards the Alaska Peninsula Saturday morning and
into the Gulf on Sunday.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 121 127 130 131 175 176 352
         Heavy Freezing Spray Warning 160 180
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MV
MARINE/LONG TERM...CK



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