Gale Warning 512, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 AM AKDT Wed Aug 7 2024

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

Wet weather continues for much of southcentral Alaska. Satellite and
radar imagery shows the front and associated atmospheric river
continuing to bring moderate to heavy rainfall to much of the area.
Over the past 24-36 hours, several inches of rainfall has fallen
across the southeast Kenai Peninsula, with many sites in the remote
Kenai Mountains recording 4 to nearly 8 inches of rainfall. Seward
has received nearly 4 inches of rainfall, with Seldovia recording
about 2.5 inches.

As we progress through the day, rain will continue for much of the
same areas, though picking up in intensity for Anchorage and the Mat-
Su Valley late this afternoon and evening. The primary flood
concerns remain for the eastern Kenai Peninsula, where 2 to 4 inches
of additional rainfall is expected in locations such as Seward and
also the Portage-Whittier area. 1 to 2 inches in addition to what's
already fallen for Anchorage and the Mat-Su may result in isolated
urban and small stream flooding, but widespread and significant
issues are not anticipated.

The front and main moisture axis finally begin to push eastward
early Wednesday night, shutting off the gap winds, with moderate to
locally heavy precipitation moving into the eastern Prince William
Sound region. Areas of light to moderate rain will continue across
the western Kenai, Anchorage, and Mat-Su through Thursday morning.

By Thursday afternoon, a shortwave rotating around the base of the
main longwave trough axis and an associated weak triple point
surface low entering the Gulf will drive another around of
precipitation into Southcentral. Widespread light to moderate rain
is expected again across the Kenai Peninsula through the Anchorage
Bowl and Mat-Su Valley, and now also portions of the Copper River
Basin, with the heaviest precipitation remaining focused near the
coast near the Prince William Sound. When all is said and done,
additional rainfall totals of 3 to 6 inches are possible for Seward
and much of the Prince William Sound coast through Thursday.

The main trough axis finally pushes eastward through Southcentral on
Friday, ending the steadier and heavier precipitation, but unsettled
conditions and areas of showers will remain across the area.

-Brown/ME

&&

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

Longwave troughing stretches south across Southwest Alaska and
the Alaska Peninsula, bringing continued widespread rain across
the region today. Multiple shortwaves rounding the rough will lift
into Southwest which will extend chance for rain showers through
Thursday night.

A high pressure ridge continues eastward across the Western
Aleutians and Bering Sea. Areas of fog are likely under the ridge
until a trough extending from a Kamchatka low brings increased
winds and rain to the Aleutian Islands Thursday, and to the
Alaskan mainland Friday afternoon.

&&

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

The long term begins on Saturday with a large upper-level low
embedded within a trough over the Bering Sea and Aleutians. Its
surface low spreads across the entire Bering while pushing its
front over the central/eastern Aleutians and into Southwest AK.
This wind-wrapped system is expected to bring widespread rain to
much of the aforementioned regions. The upper trough will pivot
across the rest of Mainland AK through Tuesday, spreading rain
eastward across the rest of the state. The EC/GFS solutions are
still in favor of high pressure building over the Bering and
Aleutians at the end of the weekend and into the start of the next
week. However, the latest Canadian runs look to form a transient
shortwave ridge before bringing a strong upper low and trough
quickly across the Aleutians. The EC/GFS eventually form an upper
trough much later in time. Overall, expect wetter conditions for
Southwest and Southcentral AK and generally drier conditions
across the Bering and Aleutians, following the trough.

-AF

&&

.AVIATION...

PANC...An occluded front moving through the Gulf will bring
continued rain showers overnight into early tomorrow morning. This
afternoon and evening, gusty easterly winds ranging from 15 to 20
knots are likely. As waves of moisture move over the airport,
lowering ceiling heights and visibility will cause a VFR to MVFR
conditions. A brief period of dry conditions is likely tomorrow
morning. However, a short wave is likely to bring another round of
rain and easterly winds to Anchorage tomorrow afternoon/early
evening and southerly winds and lingering showers in the late evening.

-DJ

&&