Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 241323

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
523 AM AKDT Sat Mar 24 2018


A weak, convoluted upper level pattern is currently affecting much
of southern mainland Alaska. A ridge over the area is dissipating
as a separate, stronger shortwave ridge moves into Southwest
Alaska. Meanwhile, polar troughing associated with an upper level
low over Kamchatka, has developed a stronger jet over the central
and western Bering with the axis of the trough over the western
Bering. This is helping maintain a surface low over the western
Bering just north of the Aleutians, which will be making its way
towards the Pribilofs today. The remnant clouds of an essentially
dead upper level front are moving over Southcentral as of this
writing early this morning, with continued dissipation expected.
Mainly clear conditions remain over much of Southwest Alaska,
except along the Kuskokwim Delta, where an area of fog that made
it just into Bethel last night developed. The aforementioned storm
system over the western Bering is causing gusty winds,rain and
snow through much of the rest of the Aleutians and Bering. Rain
will ultimately win out later today as warmer air moves in. For
Southcentral, everything is quiet under the weakening upper level



The models start out in decent agreement, but become increasingly
divergent Sunday night into Monday. The tracks of two lows
represent the largest disagreements between the models. With the
Bering low, the GFS and NAM are the furthest north, the EC is in
the middle and the Canadian is well south of the others. In
regards to this low, there is slightly better agreement at this
point in time than yesterday`s models.Little change to the
forecast in regards this low was made.

A second low developing near Kodiak Island Sunday night is the
other low. Model differences in the upper levels are making for
similar differences in the track of the surface low, and its
associated fronts and precipitation. The foreign models keep the
low further south in the Gulf, while the American ones track the
low much closer to the coast. The difference is in precipitation
amounts for the Prince William Sound area primarily. Although winds
and other factors are dependent on the eventual track of the low.
The American models were chosen as they represented the least
change to the previous forecast. At this point there is not much
telling which track will win out, as the upper level wave causing
it is still out near Kamchatka and has barely formed.


PANC...VFR conditions and light winds will persist. The upper
level clouds over the area early this morning will dissipate by


A few mid to high clouds will transit Southcentral this morning
out ahead of a weakening upper level trough. Otherwise, another
dry day with seasonable temperatures is on tap across the region.
Gusty winds over the western Gulf/Kodiak Island and western Prince
William Sound this morning will die off this afternoon as a weak
surface low over the Gulf exits to the east and an upper ridge
slides in from the west. Meanwhile, a short-wave will drop southward
through the Copper River Basin this morning and into the
northeast Gulf this afternoon, helping to drag some marginally
cooler air southward. This will help kick up some locally gusty
winds in the Valdez/Thompson Pass area.

A frontal system associated with a storm in the Bering Sea will
make its way to Kodiak early Sunday morning, with snow spreading
northward then changing over to rain. A triple point low will
develop east of Kodiak Island Sunday afternoon leading to
strengthening of winds across the Gulf coastal waters. This low
will lift northward, but remain south of the Kenai Peninsula.
Strong easterly flow out ahead of it Sunday night through Monday,
will lead to downslope drying west of the Kenai and Chugach
Mountains, with the bulk of precip confined to the Gulf coast.
While the air mass will be cold enough to support mostly snow,
surface temperatures will largely be above freezing along the
coastal zone. Thus, this does not look like a big snow producer
near sea level and some places may actually mix with rain.


An upper level ridge over Southwest Alaska will continue to shift
east through the day while an approaching frontal system in the
Bering increases southeasterly winds along the coast. Initially
the front will only brush the western most Kuskokwim Delta coast
this afternoon, and then remain offshore through the evening.
A more southern portion of the front will lift northeast across
the Alaska Peninsula and Bristol Bay Saturday evening through
Saturday night, and the continue inland over Southwest Alaska
Sunday morning. The greater Bristol Bay area looks in the best
position to pick up the most snow with this system with areas of
blowing snow developing in the locations with stronger east
southeasterly winds, particularly downwind of gaps in the
Alaska/Aleutian Range.


The next area of low pressure, which crossed into the southern
Bering overnight, will continue to deepen as it tracks to the east
northeast through the weekend, arriving just to the north of the
Pribilof Islands Sunday afternoon or evening at its maximum depth.
The low, becoming vertically stacked at this point will continue
slowly on to the east northeast arriving along the Kuskokwim Delta
Coast Tuesday morning. To the west of this broad low,
northwesterly flow will spread cold air across the Bering.


.LONG TERM FORECAST (Days 3 through 7)...
Extended forecast for Sunday and Monday remains on track, with a
low in the Bering Sea trailing a front through Southwest Alaska
and then developing a triple point low south of the Aleutian chain
and moving it onshore in the Gulf Coast. This system still looks
like it will weaken rapidly as it moves northward, dumping most of
the precipitation along the Gulf Coast. After this system moves
through, uncertainty in the model solutions remains high, as the
run-to-run consistency has been poor. Yesterday`s ridge on
Wednesday is now a strengthening low, with varying positions and
speeds in the Gulf of Alaska, depending on which model solution
you choose. General track currently pushes this next low to the
northeast by Thursday, but where the low moves onshore will have
much effect on how much precipitation falls along the Gulf Coast
and when. Currently, EC is the fastest and furthest west
solution, with the Canadian Regional taking the Red Lantern award
as it pushes the low into the Panhandle, and the GFS solution
lying somewhere in the middle. Meanwhile, all three models show a
ridge building in the Bering Sea, which is consistent with
yesterday`s forecast. For Wed through Fri: high confidence in
improving weather for Southwest, the AK Pen and Aleutians, with
moderate confidence that a low will affect the eastern Kenai and
Prince William Sound. Amounts and locations of precipitation east
of the Kenai Peninsula are still highly uncertain for the end of
the week.&&

MARINE...Gales: 130 131 170 173 175 177 180 181 185 411 412 413.
         Heavy Freezing Spray: 181.



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