Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 241240
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
440 AM AKDT Thu May 24 2018

.ANALYSIS AND UPPER LEVELS...
Weather across the state this morning is similar to what has been
observed over the last few days. A stacked Bering low currently
north of the central Aleutians is slowly moving southeastward. A
strong jet streak remains in place on the south side of this low,
creating a wide swath of zonal flow over the North Pacific. The
leading front now extends well into the Gulf and a second low is
attempting to form behind it in the southwestern Gulf.

A weak shortwave trough over Southcentral is generating rain
showers along the coastal areas of the northern Gulf. Rain showers
are also spreading in ahead of the trough across southwest Alaska.
Sunshine should become more prevalent today across Southcentral
as offshore flow increases throughout the day. Additionally,
easterly winds will enhance downsloping along the Chugach,
effectively drying out any lingering moisture between the
dissipating shortwave and the incoming front in the Gulf.

&&

.MODEL DISCUSSION...
Models are in good agreement with the Bering low timing and
position through the next 36 hours. Disagreement begins to arise
as the low moves into the Gulf 48 hours from now. Additional model
runs will hopefully resolve timing and placement.

Forecasters preferred the GFS/EC solution for the triple point
low forming behind the leading edge of the front in the Gulf. The
previous NAM solution positioned this low well off course from
the GFS/EC solutions, however this morning, the NAM has caught up
with both the GFS and EC solutions, giving forecasters greater
confidence on the position and timing.

&&

.AVIATION...
PANC...VFR conditions are expected to persist through the TAF
period. Gusty southeast winds will pick back up by this afternoon
as a front approaches the north Gulf Coast.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Thu and
Fri)...
While the synoptic pattern will not change much for the next
couple of days, there will be hints of summer in the air. First,
the low that had been position over the Gulf the past several days
is now only a weak wave stretching out along the Northern Gulf
Coast. It continues to push moisture from east to west, so expect
mostly cloudy skies to start the day from the southern Copper
River Basin through Prince William Sound. Showers will continue
along the North Gulf Coast this morning as the wave continues to
peter out. With easterly flow though, there should be a fair
amount of dry air and clearer skies in the lee of the Chugach and
Kenai Mountains (Anchorage through Homer).

Then attention will shift to another weakening frontal feature
sliding into the Gulf later today. This system will allow the
gradient over much of Southern AK to shift to an offshore
direction. This will usher drier air (sunnier skies) across the
area, and should help to suppress shower activity. As this
happens and inland areas can heat up a bit more than coastal
areas, we expect rounds of gusty southeast winds to develop each
afternoon through places like W Anchorage, Palmer, and the Copper
River Basin. For Kodiak, the front will only serve to reinforce
the wet weather with onshore flow. A weak low will develop just to
the east of the island along the decaying front later tonight.
The low will help focus rain right into the northeast side of the
island and Kodiak City.

By late Fri, the front from the Gulf will begin to stretch out and
weak along the North Gulf Coast. This will keep rain going along
the coast, especially from Cordova over to the Southern Kenai.
However, aside from a few showers over the mountains, most inland
areas will remain dry. The front will cast a healthy swath of mid
and high clouds across the area, but with increasing solar
radiation, we still expect mild temperatures in the afternoon
hours.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The easterly wave pushing across northern portions of the
Kuskokwim Valley early this morning, moved in a bit faster than
early model runs had been suggesting. As this wave continues west
today it will continue spreading precipitation along with it and
into northern portions of the Kuskokwim Delta. Elsewhere the
diurnal pattern of showers forming in the afternoon and evening
will continue. By Friday the thermal trough will return to
Southwest Alaska and then strengthen on Saturday increasing the
potential for isolated thunderstorms along and near the trough
axis both days.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The vertically stacked low in the southern Bering will cross the
the eastern Aleutians this evening and then continue off to the
southwest tonight and Friday. Ridging will build in across the
Bering from the west behind the low, increasing northerly flow
over the eastern Bering and across the Alaska Peninsula and
eastern Aleutians Friday and Saturday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Starting Saturday, an upper level low will move over the southern
portion of the Gulf of Alaska while a ridge builds over the
western half of the Bering Sea and into SW Alaska. A front
extending out ahead of the associated surface low in the Gulf will
spread rain and wind over the Panhandle while leaving most of
southcentral dry as a weak upper ridge axis tries to build over
over the central and western portions of the state. This should
set the stage for a decent Memorial Day weekend over most of
southcentral and SW Alaska with a few breaks in the cloud cover
and mostly dry conditions, though diurnally driven rain showers
will likely develop over the higher terrain in the late afternoon
hours. Right now, Memorial Day looks to the nicest day of the
weekend over most of the southern mainland as the upper ridge axis
moves over southcentral allowing clouds to scatter out a bit
more, though temperatures look to be right around average for this
time of year.

Models show some disagreement regarding how long
this period of somewhat nicer weather will last, with the EC being
the more progressive solution moving the next front into the SW
mainland by Monday afternoon, while the GFS brings the front
across a bit later on Tuesday. Either way, models are consistent
in redeveloping the upper low over the Bering by early to mid next
week bringing a continuation of the cooler and wetter pattern
that has been plaguing the region since mid April.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KO
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JER
LONG TERM...KVP


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