876
FXAK68 PAFC 060141
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
541 PM AKDT Sun May 5 2024

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

A broad trough of low pressure exists over much of the Gulf with
weak ridging poking in over the AlCan border. To the west, an area
of upper level diffluence has set up over Bristol Bay. The main
weather feature for the next 24 hours will be an easterly wave
currently moving over the Copper River Valley that will move west
over the remaining portions of Southcentral. This will overspread
precipitation as it moves east and interacts with the area of
diffluence. Guidance also indicates a deformation band setting up
somewhere from the southern Mat-SU south to the western Kenai
Peninsula. The main uncertainty in the forecast is how the
easterly wave will interact with the diffluence and where the
deformation sets up. This forecast package reflects a band that
will move east from the Mat Valley and Anchorage area in the early
morning, moving east to the western Kenai and Susitna Valley
later in the morning to afternoon hours. Most areas are looking at
.1 to .3 inches of precipitation, but should this band stall over
an area, or the convection tonight be more intense, totals near
0.5 inches can be expected.

Moving into Tuesday there are no discernible, stronger features,
so afternoon showers near the terrain can be expected, with higher
chances along the coast and PWS with onshore flow. Some breaks in
the clouds may also lead to warmer temperatures in spots. On
Wednesday a compact low will move near the Gulf coast and PWS,
leading to steadier precipitation for coastal communities and
otherwise drier conditions inland.

- CJ

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE SEA AND THE ALEUTIANS
(Days 1 through 3)...

Scattered rain and snow showers will continue through mid-week.
Freezing spray, heaviest just south of the ice shelf from St.
Matthew Island to Nunivak Island and northward, is expected today
into tomorrow evening. An Arctic High will cause northerly winds
through the Bering Strait this evening through tomorrow afternoon.
Tonight`s push of cold air is expected to be most prevalent along
coastal areas of the Kuskokwim Delta southward to the Alaska
Peninsula and along the Bristol Bay coast. Persistent onshore
winds will keep tonight and tomorrow`s temperatures below normal
under a mostly cloudy sky. Tuesday morning, low pressure from the
Bering Strait will bring a reinforcing push of cold air southward
to the Alaska Peninsula and Aleutians by the evening hours. This
low will join a weaker one near the Pribilofs Tuesday. Strong
northerly winds from these lows joining will result in heavier
snow and rain showers for areas west of Dutch Harbor. Current
models track the joined low southward through the Central
Aleutians later in the week.

-DJ

&&

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

Broad troughing stretches from the western Aleutians towards the
Gulf of Alaska, with multiple surface lows tracking across the
Aleutians and into the Gulf. Precipitation along coastal regions
of Southcentral, including Kodiak Island, will persist through
much of the long term. Some precipitation will likely spill over
into Southwest Alaska as the Gulf low moves over the Kenai
Peninsula on Thursday. Since the low developing out near the
Western Aleutians on Thursday stays south of the Aleutians as it
travels towards the Gulf, precipitation will likely diminish over
Southwest by late Friday. An upper-level ridge attempts to build
through the weekend across portions of the Bering and Aleutians,
however, each model solution shows differences in the way the
ridge interacts with the surrounding lows/troughs.

&&

.AVIATION...

PANC...While the Southeasterly winds out of Turnagain Arm are
expected to develop again by early evening, one difference is
that they will likely not diminish much overnight, but stay over
the airport overnight and through the day on Monday. This is due
to an upper level short-wave that will move in from the northeast
overnight though Monday morning. It is looking more likely that
this wave will also bring in rain from late tonight though Monday
morning. Ceilings and visibility will drop near MVFR levels and
may go MVFR for a time.

&&

$$