Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 221341
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
541 AM AKDT Fri Mar 22 2024

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

Early morning water vapor satellite imagery and H5 heights were
showing the axis of the high amplitude ridge near the ALCAN border,
and a trough moving through Southwest Alaska. The trough appears to
be taking a more negative tilt than the 06Z model consensus is
showing with a dry slot working across Kodiak Island and up into the
southern Cook Inlet. This is also noted in the 12Z Kodiak sounding
and the reflectivity signatures off the Kenai radar as precipitation
works up the inlet this morning. Kodiak may still see a few showers
later this morning, but should generally remain dry until later this
evening as a stronger system approaches. As precipitation continues
to work up the inlet this morning, near surface temperatures will be
a primary factor in precipitation type. Areas along the western
Kenai Peninsula and Cook Inlet are hovering near freezing to several
degrees below freezing, so will likely see most locations start out
as snow before changing over to a rain-snow mix or all rain as
temperatures warm through mid-morning. In addition, precipitation
chances will also decrease from south to north as the shortwave
lifts up into Southcentral. Best chances for more steady
precipitation continues to remain along the eastern Kenai and Prince
William Sound where lower elevations will see a rain-snow mix or all
rain. Regardless, only minor accumulations if any are expected for
lower elevations with several inches possible for the coastal
mountains of the Kenai and Prince William Sound. Turnagain Arm will
see winds increase this morning and afternoon as the pressure
gradient increases, and the set-up still looks to favor bending some
of the southeasterly winds into south and west Anchorage.

The lack of cold air with today`s system will result in the
continued period of mild temperatures for Southcentral. Shortwave
ridging behind this system will also help to keep temperatures mild
heading into the weekend.

The next system is still on track with models generally in
agreement with the track and timing of precipitation. The parent
low will lift towards the central Aleutians today with several
shortwaves rotating around the low. A new low will develop along the
frontal boundary as it lifts north towards the AKPen and will
eventually become the new dominant low as it deepens and crosses the
Aleutians Saturday night. This will result in a period of rain for
the eastern AKPen, Kodiak Island, and the eastern Kenai beginning
tonight and continuing into early next week. Persistent easterly
flow will develop across the western Gulf allowing for the bulk of
the precipitation to fall across the Kodiak Island and the eastern
side of the Kenai and downslope strengthening for the western Kenai
up through the Mat-Su Valley and keeping these areas mostly dry.
Temperatures look to remain fairly warm with the primary
precipitation type being rain in the lower elevations.

- PP

&&

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

Key Messages:

* Rain over the Kuskokwim Delta and Bristol Bay transitions to a
  mix of rain and snow this afternoon with minimal accumulations
  through this evening.

* Gusty conditions return to the Aleutians and Southwest Alaska
  over the weekend with the arrival of the next N Pacific low and
  front.

* 3 to 5 inches of snow and blowing snow remain possible for the
  Pribilofs on Saturday and Sunday.


Discussion:

Nighttime microphysics satellite imagery shows an upper trough
draped over the eastern Bering/Southwest Alaska coast this
morning. A pair of shortwaves within the trough, one pushing
through the Kuskokwim Delta, and a second pushing into Bristol
Bay, help to produce rain from Bethel down to Dillingham. Cooler
air on the backside of trough will gradually transition rain to a
mix of rain and snow through this afternoon. Any accumulations
will be light and likely less than an inch for lower elevations.
Precipitation comes to an end later this evening and tonight as
the upper trough departs the region to the northeast.

Attention then turns to an approaching North Pacific low south of
the Western Aleutians Friday night, which lifts into the southern
Bering by Saturday morning. This new low will see gusty conditions
return to Southwest Alaska while also bringing snow and blowing
snow to the Pribilof Islands. The Pribilof Islands will be
favorably positioned in respect to the Bering Sea low (northwest
side), which should see temperatures maintain precipitation as all
snow through early next week. Small craft to gale force
northeasterly winds are forecast all of Saturday and potentially
through Sunday as well. While snow is forecast for the Pribs,
southerly and southeasterly flow feeding into Southwest Alaska and
the AKPEN will likely see a mix of snow and mostly rain through
the weekend, again with little to no accumulation expected.

BL

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)...

The upper level ridge over the Mainland continues to weaken
slowly through the forecast period. Forecast models are well
clustered to start, but become undone through midweek. Over
Western Alaska and the Eastern Bering, an elongated low stretching
from the Arctic to the North Pacific oscillates East-West with
the transient shortwaves flowing through the system. A weak
Russian Far East high wobbles over the Western Bering through
Thursday. The main track of the surface systems coincides with the
tighter gradient across the Southern portions of the state.

Southerly airflow over the Interior continues, but is being
eroded in the West somewhat by Arctic air with the Bering trough.
A well developed surface low in the Southeastern Bering anchors a
front that extends across the Gulf of Alaska, and trails over most
of the Aleutians through Tuesday. A second well developed North
Pacific low and front enter the Alaskan waters for Tuesday and
moves along and just South of the Aleutians through Thursday,
before slipping into the Eastern North Pacific.

Gusty Northerly winds spread over the Central and Eastern Bering
for Monday and Tuesday, crossing the Eastern Aleutians by
Wednesday. Snow will predominate over Western Alaska and the
Pribilofs, becoming mixed with or changing to rain across from the
Aleutians,and Alaska Peninsula through Tuesday. The second low
and front bring another round of rain or mixed rain and snow late
Tuesday through Thursday across the Aleutians. The front extending
across the Gulf will spread mostly rain from the AKPEN and Kodiak
Island across to the Canadian Border. Rain, possibly mixed with
snow invades the Southcentral Interior through Wednesday.

Kutz

&&

.AVIATION...

PANC... VFR ceilings and visibility are expected to prevail
through the TAF period. Southerly flow early this morning will
turn more southeasterly through the morning and into the afternoon
as a weak frontal system and shortwave lifts northward through
the western Gulf. Conditions should remain mostly dry today as a
result of the southeast flow. The main core of southeasterly
Turnagain Arm winds should also remain out over the Arm while
barely clipping the terminal this afternoon into the evening
hours. The southeast winds will turn more northerly early Saturday
morning as stronger down-inlet flow ensues ahead of the next
front to lift northward through the western Gulf on Saturday.

&&

$$


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