textproduct: Anchorage

..Key Messages and Active Advisories and Warnings

* Bitterly cold air temperatures and wind chills continue across Southwest Alaska. Extreme Cold Warnings remains in effect for Southwest Alaska.

* A Winter Weather Advisory has been issued for the Kuskokwim Delta, Western Capes, Northern Bristol Bay coast, and inland Bristol Bay through Saturday morning. * A Blizzard Warning remains in effect for Adak and Atka for this afternoon through Friday afternoon.

* A Special Weather Statement remains in effect for Nikolski, Unalaska, and Akutan for rain changing to snow showers tonight into Friday. Snow showers and gusty winds could lead to periods of reduced visibilities. * Arctic air and gusty winds will bring potential for extreme freezing spray along the ice edge.

Discussion:

The overall synoptic setup has not significantly changed since yesterday. A ~970 mb low spinning south of the Aleutians with a warm front draped across the Central Aleutians is spreading stratiform precipitation from Adak to Cold Bay in the form of rain and snow, dependent on location relative to the front. Cold air is surging southward across Adak and Atka, transitioning rain to snow and as winds pick up, blizzard or near blizzard conditions are expected, with 3 to 5 inches of snowfall possible. The warm conveyor belt can be seen in action on IR satellite as clouds stream poleward just ahead of the cold front attached to the system in the North Pacific. With an arctic high to the north and lower pressure to the south from the surface low, pressure gradient induced winds are being generated across the Bering and Aleutians, giving some locations blizzard conditions and others blowing snow concerns. An upper level trough coincidentally is digging southward along the Southwest Alaska coast, which has helped to induce a corridor of gusty winds for portions of the Southwest that is streaming southwestward out of the Kuskokwim Delta coast and the Bristol Bay region and across the eastern Bering. This setup for coastal Southwest Alaska and areas just inland has prompted the issuance of a Winter Weather Advisory for blowing snow from 40 mph wind gusts through Saturday morning. By Saturday morning, winds should begin to decrease in intensity with the upper level trough passage and the surface low south of the Aleutians moving farther away from the region, which in turn will weaken the surface pressure gradient between the low and the arctic high to the north. By the weekend, cold temperatures and northerly winds will remain over almost the entirety of Southwest Alaska, Bering Sea, and Aleutian Chain.

-AM/KM

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

The active weather pattern is expected to continue for the first half of next week. The upper level low will still be over the Interior and southwest Alaska on Sunday, keeping Southwest Alaska entrenched in the cold with part of Southcentral still being in lingering snow on the tail end of the weekend system. The upper level trough will not move a lot through Monday, but what does change on Tuesday is that the trough will edge westward as a strong low moves into the Gulf of Alaska from the south. There is a reasonable degree of uncertainty as to the exact strength and track, but what looks likely is that this low will end up moving into Prince William Sound or to the east of it. This will keep Southcentral in the snow with only Cordova in a position to see potential for a switch to rain from the snow. This system has the potential to produce strong winds and heavy snowfall for coastal regions including the coastal mountains Tuesday and Wednesday.

High surface pressure will remain centered over the Western Bering Sea through the period. With the upper level trough remaining over Southwest Alaska and the Bering Sea, this will keep Southwest Alaska as well as the Bering Sea/Aleutians/AK Peninsula with cold temperatures and stiff northerly winds. While most of the precipitation will remain east of the Alaska/Aleutian Ranges, the Alaska Peninsula and eastern Aleutians have the potential for periods of heavy snow showers that develop off the ice edge and stream into those areas.

AVIATION

PANC...Patchy areas of low stratus and fog have persisted across parts of Anchorage this afternoon. Occasional periods of IFR ceilings/visibility will remain possible at the terminal this evening with transient fog or stratus, but increasing north winds should steadily decrease this threat with time. Northerly winds will pick up to 10 kts or a little greater by late tonight and Friday morning. These elevated northerly winds could cause some instances of drifting snow tonight and Friday morning. Predominant ceilings will begin to lower some Friday afternoon ahead of another potential snowfall event arriving later on Friday evening.