textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages: - Isolated marine lightning over the central Gulf of Alaska is possible through this evening.

- Clearing skies and cool temperatures will lead to another night of patchy fog and widespread lows near or below freezing.

- Gap winds return to Southcentral as early as Friday morning out ahead of a gale force front that will lift northeastward across the northern Gulf.

Discussion:

The first part of the short term forecast will remain relatively quiet. Currently, the only real feature of interest is ~1001 mb low meandering across the eastern Gulf. Due to colder air aloft steepening lapse rates and therefore increasing instability, an isolated lightning strike or two cannot be ruled out this evening across the central to eastern Gulf. Elsewhere, clear skies and light winds will allow for temperatures to fall quickly tonight from anywhere from the 20s to near 30 degrees for the Copper River Basin and Susitna Valley, and overnight lows bottoming out in the mid 30s for the Anchorage Bowl. Areas of patchy fog are possible Thursday morning from Big Lake to Talkeetna with a combination of radiational cooling and residual moisture from recent rainfall.

Attention then quickly shifts to the west where a very strong system is progged to enter the western Gulf in the form of a gale force front with storm force gusts by Thursday afternoon. While the parent area of low pressure remains in the Bering, models show the front lifting northeastward across the Gulf through the rest of the short term. Winds will first impact Kodiak Island starting Thursday afternoon. On the precipitation side of things, rain chances increase first for Kodiak Island, the eastern Kenai Peninsula, and Prince William Sound locations Thursday afternoon and periods of locally heavy rain are possible given upslope enhancement. Coastal ridging is on track to build across the northern Gulf coast on Friday, which will lead to a gradual increase in gap winds for the Copper River Basin, Knik River Valley, and Turnagain Arm. In contrast to coastal locations, southeasterly winds ahead of the front will create a "downslope hole" for the Anchorage Bowl, keeping this area mostly dry through Friday and Saturday as the front continues its trek northeastward across Kodiak Island. Also, for Friday morning, as the gale force front aligns with Kamishak Gap, expect these winds to ramp up and continue through Friday afternoon.

As the east to west oriented pressure gradient maximizes along the Gulf coast from the coastal ridge Friday afternoon and the southeasterly winds from the front itself aligns with the Turnagain Arm, expect Turnagain Arm winds to increase here as well. Due to the parent low location out west signaling down-inlet flow, the Anchorage Bowl seems to be less of a concern than the Hillside, where at elevation wind gusts will likely be ticking up in the neighborhood of Wind Advisory criteria. The consensus with this afternoon forecast package is to lean into the 75th percentile NBM, and it shows that wind gusts fall just short of Wind Advisory criteria for the Hillside, but it also depicts (as expected) higher winds just above the Hillside. Current forecast confidence is still in the medium range (40 to 60 percent) for Hillside wind gusts, but should this evening and overnight model runs come in stronger, this will most likely necessitate a wind hazard product. Conditions could potentially become hazardous from gusty conditions along the Seward Highway along the Turnagain Arm late Friday into Saturday morning as the highway could become clipped with strong wind gusts. Again, the low location out west will be key in determining the extent of impacts from the Turnagain Arm wind. As the parent low located over the eastern Bering begins to move northward, model consensus is that the Turnagain Arm winds will begin to bend northward, but this currently does not look to coincide with the strongest winds from frontal alignment with the Turnagain Arm gap. Stay tuned.

-AM/Rux

LONG TERM FORECAST (Days 4 through 7)

An upper level stationary low over the Interior Mainland late this weekend causes a trough to dig into the Bering Sea through the middle of next week. This trough brings persistent northerly/northwesterly winds to the Central and Western Aleutians through mid-week. Additionally, the flow brings low pressure systems through this area Monday and Wednesday resulting in rounds of precipitation and gusty winds through the bays and passes. The exact track of the mid-week storm through the Aleutians is uncertain with the general consensus of a more southerly route looking likely at this time as winds turn more northerly. In Southwest Alaska, onshore flow and weak ridging sets up between the lows' passing.

For Southcentral, multiple lows are projected to enter the Gulf of Alaska bringing rain and wind to Kodiak Island and both the Eastern Kenai Peninsula and the Prince William Sound coasts from late this weekend and into the middle of next week. There are signals of a weak ridge in the Gulf of Alaska arrives late next Wednesday.

AVIATION

PANC...VFR conditions will persist through the TAF period.