765
FXAK68 PAFC 171248
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
448 AM AKDT Fri May 17 2024

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

A strong shortwave rotating south and east around a strong
longwave trough over the Bering Sea will continue to move south
and east into the Central Gulf of Alaska today and weaken further
as it pushes into the Eastern Gulf of Alaska on Saturday. A weak
surface low pressure system associated with the shortwave is
currently located 100 nm east of Kodiak Island and will weaken
further as it moves over the Gulf of Alaska today and over the
southern Panhandle this evening. Rain showers currently noted on
Radar over the Northern Gulf of Alaska, Prince William Sound and
the Kenai Peninsula will diminish today as weak ridging both aloft
and at the surface push into the Gulf of Alaska and merge with
High Pressure noted over the Yukon and Eastern Alaska.

The break between storms in the Gulf of Alaska will be short
lived as a strong low over Bristol Bay and supported by a deep and
unseasonably cold upper level low pressure system over the Bering
Sea will strengthen on Saturday as it pushes east over the AK
Peninsula on Saturday and over Kodiak Island Sunday morning. Ahead
of the low a surface ridge will push north into the northern Gulf
of Alaska and will bring some breaks in the clouds as slightly
warmer temperatures. Gusty southeasterly winds will pick up again
as the coastal ridge develops ahead of the low entering the Gulf.

Through the day on Saturday the strong and unseasonably cold
upper level low will slide from the Bering Sea into the western
Gulf of Alaska, sending another period of precipitation back into
Kodiak Island. As the upper low and accompanying surface low move
into the western Gulf, precipitation will also overspread the
eastern Kenai Peninsula through Sunday morning. Confidence remains
low in regards to the northern extent of precipitation through
Sunday as there is still disagreement among model guidance on
where the upper low ejects into the Gulf; a moderate, more steady
rain may also make it further north into the Prince William Sound
and other areas along the coast of Southcentral Alaska. The
Eastern Kenai and Prince William sound will see the heaviest
precipitation while the Western Kenai, the Anchorage Bowl and the
MatSu will see lesser amounts with drying downslope flow and gusty
southeasterly gap flows.

-CC

&&


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

The forecast remains largely on track, with only minor updates to
wind speed and precipitation type/amounts. The low that brought
rain to parts of Southwest Alaska overnight is weakening as it
exits into the Gulf. While much of Southwest Alaska remains under
overcast skies, radar shows that precipitation has largely tapered
off. The only major item of note this early morning for Southwest
is a bank of fog and low stratus currently making its way into
Kuskokwim Delta.

A different story is unfolding in the Bering Sea and Aleutian
Islands, where satellite imagery shows a low in the Northwest
Bering, a North Pacific low near Amchitka, and a front extending
between these two features. Much of the action this morning is
currently over the Central Aleutians, where light rain has just
begun to fall. Few impacts are expected for the Central Aleutians;
the front will still be fairly weak as it moves across the
Central Aleutians through the early afternoon. Instead, the brunt
of the stronger winds and heavier precipitation will be felt in
the Eastern Aleutians and Southwest Alaska on Saturday as the
lows merge and draw in moisture from the North Pacific.

While this storm system doesn`t look to be exceptionally
impactful, there are a few items of note. One is that gusty
southeasterly winds will overspread much of Southwest Alaska
through Saturday, with the strongest winds (gusts of up to 50 mph)
expected in interior Bristol Bay near Kamishak Gap. Winds will be
enhanced by the terrain as well as a tightened pressure gradient
between higher pressure in the Gulf and lower pressure near
Bristol Bay. Secondly, cold air in place ahead of this approaching
front will likely lead to light snow for Nunivak Island and the
Kuskokwim Delta coast from tonight into Saturday morning. The
current forecast is for about 2 inches of snow, though daytime
highs ranging from the mid 30s through low 40s should help to melt
the snow before day`s end.

Further west, the Central and Western Bering/Aleutians will see
active but generally low impact weather as two weak storm systems
move through, one on Saturday and one on Sunday. The stronger of
these two systems will be Sunday`s, which will bring winds at
small craft speed (25 kt) and light rain, as opposed to sub-small
craft wind speeds and scattered rain showers for Sunday`s system.

-KC

&&

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

The extended forecast looks to be a brief transitional period as
the longwave pattern reloads itself. Currently the pattern is
driven by an anchoring trough over Siberia with a cold pool
extending into the Bering Sea and southwest Mainland. Over the
weekend, a new stronger shortwave trough propagates within the
east Asian jet and into the Bering Sea which will re-orient the
longwave trough to look much the same as it currently does despite
the first system moving from the Bering Sea into the Gulf of
Alaska. For Southcentral Alaska, the northern extent of the Gulf
low pressure will potentially bring rain to coastal areas but
leave interior areas dry with continued clouds and slightly below
normal temperatures over the weekend.

What does this mean for sensible weather? Another slug of tropical
moisture will bring rain to the southwest Mainland and Aleutians
early next week along with gusty southerly winds. The building
ridge ahead of that front will bring at least of day of drier
possibly sunny weather, however, with the trough out west
positioned over the Bering Sea it is more likely than not that we
get another disturbance or moisture plume over Southcentral, but
confidence is lower and uncertainty high as the pattern
transitions. Stay tuned.

MTL

&&

.AVIATION...

PANC...VFR conditions are expected to persist on Friday as a weak
low over the Gulf of Alaska departs the region to the southeast.
Winds should remain light and below 10 knots.

BL

&&


$$