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FXAK68 PAFC 060033
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
433 PM AKDT Wed Jun 5 2024

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

Following yesterday`s fun in the sun, Anchorage had record
setting rainfall today, with a rainy day had across most of
Southcentral. Driving this pattern shift is a low pressure system
in the northern portion of the Gulf of Alaska, spinning multiple
waves of moisture in from the southeast. A series of short-waves
are rotating around the north side of this low, with areas of
moderate rain embedded within the larger area of light rain. As
such, rainfall is likely to continue for coastal Southcentral, but
slowly begin to taper off in Anchorage this evening. High and low
temperatures to be slightly cooler across Southcentral than
yesterday given the widespread cloud cover.

Looking forward, the Gulf low is weakening as it tracks to the
north Gulf coast tonight, with the upper center opening up into a
trough. Models are coming together regarding a more northern
system, raising the confidence on gusty winds through the gaps
tomorrow and continued rainfall across the northern Gulf coast. As
the upper low approaches Southcentral tonight the short-waves
bringing all of the rain today will begin to exit off to the north
and west. Precipitation over Southcentral will diminish and
become more showery in nature. What is certain is that
strengthening onshore flow behind the remnants of the low will
lead to widespread precipitation along the north Gulf coast and
Prince William Sound regions through Thursday. Further inland on
Thursday, in the Susitna Valley, conditions are looking favorable
for some isolated thunderstorm development. Biggest key and
uncertainty currently is to what degree the skies scatter out
before peak- heating, allowing for the most optimal conditions for
development.

Gusty southeasterly gap winds are expected Thursday as the
pressure changes associated with the passing trough and marginally
warmer inland temperatures will amplify gusty wind potential. The
last of the short-waves will exit northward Thursday night into
Friday, with a weak short-wave ridge building overhead. Thus,
expect precipitation to taper off (lingering longest along the
eastern Kenai Peninsula). Friday looks like it could be a nice
day, with abundant sunshine and temperatures rebounding back into
the 60s for most areas.

Weather for Kodiak Island will be quiet the next couple days,
as they are situated away from the key features discussed above.
Guidance is in good agreement that a deep low will lift out of
the base of the long-wave trough and track up to the Gulf Friday
night/Saturday. This would bring a return of rain and wind to
Kodiak as early as Friday evening.

-CL/SEB

&&


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

An arctic upper level low continues to dive south through the
Bering into the Central Aleutians through tonight, with scattered
snow showers expected to persist across the Pribilof Islands
through tomorrow morning. Further south across the central
Aleutians, showers with mixed precipitation will continue through
tomorrow as the upper level low meanders over the Aleutian Chain.
As an upper shortwave swings around the base of this trough, a
surface low/low complex will form near/over the eastern Aleutians
and swing westward between the Central Aleutians and the Pribilofs
through tomorrow. This new surface low will draw notable North
Pacific moisture northward with persistent showers expected across
the eastern Aleutians and Alaska Peninsula Thursday afternoon
through at least Friday afternoon. Any remaining snow showers
however will transition to rain showers and will persist for at
least a few more days as the upper low remains nearby and the cold
airmass slowly moderates.

As for Southwest Alaska, scattered showers with mixed
precipitation continue across the Kuskokwim Delta through late
this evening. Meanwhile, widespread light to moderate rain showers
continue to move over the Western Alaska Range and may make it as
far west as Sleetmute tonight through tomorrow morning. A few
isolated thunderstorms are also possible for the western Alaska
Range late Thursday afternoon/evening as a few easterly waves move
through with marginal instability. There is still some
uncertainty with the location and timing of any convective
initiation as there is still disagreement on the location and
timing of these weak upper shortwaves.

High temperatures for the Pribilofs and Aleutians will struggle
to make it out of the upper 30s to lower 40s over the next couple
of days. High temperatures for Southwest Alaska however will trend
warmer with highs climbing into the 50s and 60s by this weekend.

-ME

&&


.LONG TERM FORECAST (Days 4 through 7) Sunday through Wednesday...

The Alaska Weather Map is becoming a bit busier through the
forecast period. A dual centered upper level low in the North
Pacific merges to form a single closed low in the Gulf of Alaska
by midweek. An upper level ridge on Sunday moves across the Bering
and flattens out for Wednesday, as a well developed surface low
moves out of the North Pacific. A new low out of Siberia pushes
its way into the Bering, settling into the Central Bering by
Wednesday. A broad ridge remains over the Northern two- thirds of
Mainland Alaska, and continues its support of surface thermal
troughs. Forecast confidence remains good through the period,
starting with a deterministic blend before changing to a UK/EC
ensemble means.

The upper level low in the Gulf hooks up with a North Pacific
surface system to spread considerable rainfall across the
Southcentral areas from the Canadian Border, across Prince
William Sound and the Eastern Kenai to Kodiak Island and parts of
the Alaska Peninsula for Sunday and Monday. Mostly offshore gusty
winds will occur over the Gulf, but move over Kodiak Island and
the Southern Kenai Peninsula through early Tuesday. Unsettled
conditions will linger across Southcentral, bringing showers over
the area. Transient systems will bring locally heavy rains over
the Aleutians and Bering through Wednesday.

-Kutz

&&

.AVIATION...

PANC...A strong trough moving west of Anchorage will continue to
bring rain to the terminal through early evening. Ceilings and
visibility are expected to remain VFR, but a temporary reduction
to MVFR later this afternoon is still possible in heavier rain.
Expect turnagain arm winds to persist over the terminal through
late this evening, with gusts to around 25 kts possible at time.
Conditions will improve overnight with winds diminishing. The
Turnagain Arm winds will redevelop and move back over the terminal
by around noon tomorrow with gusts up to 30 kts possible.

&&

$$