963
FXAK68 PAFC 060011
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
411 PM AKDT Sat Oct 5 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Monday night)...

A very large vertically stacked low remains centered just off the
coast of Southwest Alaska this afternoon. Colder air aloft moving
in behind the front will lead to a showery regime for the next
few days. A strong shortwave rounding the base of the main upper
level low will spawn a new surface low south of Kodiak Island
tonight and lingering through early next week. There is some
spread among model guidance in the exact track of the low as it
wobbles around in the southwestern Gulf and therefore the location
of the strongest winds.

Deep south/southeasterly flow will lead to steady upslope
precipitation along the coastal mountains tonight, with steadier
precipitation also beginning across Kodiak Island as the low
develops. Flow will then gradually turn more easterly by Sunday
afternoon allowing showers and the steadiest precipitation to wind
down along the coast. However, additional shortwaves will then
lift from the eastern Gulf to the Copper River Basin, with showers
spreading inland. Model guidance has also been hinting at the
possibility of a relatively strong but compact low forming
coincident with one of these shortwaves which may briefly enhance
precipitation along the coast Sunday night into Monday morning.
The rest of Southcentral may see an occasional light shower this
weekend.

-ME

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, AND THE BERING
SEA/ALEUTIANS...

A developing low south of the Alaska Peninsula is expected to
move east and out of the day today, which should assist with
dragging the strong, eastern Bering Sea low southward. The eastern
Bering low will gradually weaken as it makes its trek southward,
crossing Unimak Island just after midnight tonight. Winds gusting
40 to 50 mph in the southern Bering Sea and central Aleutians this
afternoon will diminish slightly to around 30 to 40 mph tonight
through Sunday. On the backside of the Bering low, a swath of cold
arctic air (minus 10 Celsius in the midlevel) will be drawn south
across the Bering Sea starting tonight. Northerly winds will
increase again across the eastern Bering Sea from the Pribilofs
and Nunivak Island south to the eastern Aleutians to the Shumagin
Islands. Locations such as Cold Bay can expect peak northerly
winds, gusts of 40 mph likely, after midnight Sunday and Monday
morning. There is moderately low confidence on the exact peak
magnitude of the wind gusts however as cool, dense air becomes
enhanced as it accelerates through gaps, bays, and passes. For
Southwest Alaska, the weather will become quieter after today.
Precipitation will likely remain confined to the mountains.

Meanwhile, high pressure over the western Bering will continue to
build through Monday morning before dipping south of the
Aleutians and flattening Monday night. Dual lows, one from Russia
and one from Japan, will really put a dent in this ridge. Monday
afternoon, the low out of Russia will swing through the
northwestern Bering. Its associated front will weaken Tuesday
morning between near Saint Matthew and the Pribilofs. Chances for
precipitation quickly diminish at that time, therefore confidence
in precipitation chances are low. Although there would be
relatively warmer air advecting into the area, a few snowflakes
cannot be ruled out for the Pribilofs and Saint Matthew. The
incoming system from Japan on Tuesday to the western Aleutians
will be much warmer. Although there is some model spread in the
low center, the general track is expected to move west to east
across the southern Bering Sea with its triple point hovering
along the Aleutian Chain through midweek. Consequently, timing of
the front and its precipitation is a little bit more challenging.
Temperatures for the Aleutians are expected to be in the mid 40s
to lower 50s.

&&

.LONG TERM FORECAST (Days 4 through 7: Wednesday through
Saturday)...

The global and regional models are in fair agreement through
Friday with the persistent upper level trough over mainland
Alaska and the Gulf becoming less defined into Friday as it
begins to interact and merge with an upstream shortwave in the
Bering Sea. The Canadian model suggests the upper level close low
remain over Central Alaska. However, preferred GFS/ECMWF solution
that has the upper level low remaining over the South Central
Alaska and the northern portion of the Gulf of Alaska.

The surface low and attached fronts will quickly move over the
Central Aleutians and Alaskan Peninsula Thursday and then stall
out over Gulf of Alaska through Saturday. Scattered coastal
precipitation and gale force northerly gap winds are likely as
this impactful system crosses from the Bering Sea and into the
Northern Gulf Friday and Saturday.

High pressure will ridge into the Western Bering Sea ahead of
another North Pacific system that approaches the area early next
week.

-DD

&&

.AVIATION...

PANC...Scattered light rain showers will continue to push through
the terminal this afternoon and evening as several small
disturbances rotate through the region. Even if a shower passes
over the terminal, conditions should remain VFR with ceilings
looking to remain in the 5-8 kft through this evening and
vsby remaining VFR. Turnagain Arm winds will remain gusty with
flow generally straight out to Fire Island or turning down inlet,
but may see occasional wind gusts of 20 to 25 kts bend into the
terminal. Winds will become more northerly after 12-15Z with light
northerly winds for the terminal.

&&

$$