.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS (Days 1 through 3: This afternoon through Sunday evening)...

Showers over interior Southwest Alaska will begin to taper off tonight; although some showery activity could linger against the high terrain through Friday afternoon. A weak front will cross the Eastern Aleutians and Pribilof Islands tonight and make it to the Southwest coast Friday morning. Any precipitation associated with this front will be light and mostly confined to the Kuskokwim Delta Coast. There is some chance that very light precipitation makes it as far inland to Bethel for Friday afternoon. As light showery activity winds down across Southwest Friday evening, attention quickly transitions to what will be developing across the Bering Sea Friday evening for the weekend.

The source for what will become an active late week across the Bering and weekend for Southwest is a southward digging trough from Eastern Russia. In addition to the digging trough, a decent moisture tap from the tropical West Pacific will also be present and help deliver moderate to heavy rain at times Friday through the weekend. As the Eastern Russian trough continues to dig southward through the western Bering and into the North Pacific, numerous shortwave will lift across the Aleutian Chain and into the east-central Bering through Friday evening. The result will be moderate rain, heavy at times, across the Central and Eastern Aleutians and eventually to the Pribilof Islands as well. There will also be a corridor of southerly gale-force winds through the Central and Eastern Chain Friday afternoon and evening.

Cyclogenesis looks to take place very late Friday night to early Saturday morning as a surface low pressure develops a little north of the Pribilof Islands. Confidence continues to increase on a storm track from north of the Pribilof Islands late Friday night/early Saturday morning to around Saint Lawrence Island or a little north of there by Sunday. Moderate to heavy rain across the Pribilof Islands Friday evening moves into mainland Southwest and the Alaska Peninsula all of Saturday. Moderate rain lingers across the Lower Kuskokwim Valley and interior Southwest as orographic influence aides in ringing out moisture over the area. Steady rain across the Kuskokwim Delta and Bristol Bay becomes more showery in nature by Saturday evening and lasts through Sunday as colder air works in aloft.

As the system tracks north, it will continue to slowly deepen on its journey to the vicinity of Saint Lawrence Island and perhaps remain nearly stationary there Sunday through Sunday night. With this track, a sustained fetch of southerly to southwesterly winds is favored coming off the eastern Bering and into the coast of Southwest and especially the Kuskokwim Delta Coast. Thus, a Coastal Flood Watch has been issued for the along the Kuskokwim Delta Coast from Saturday morning through late Sunday night from the mouth of the Kuskokwim River to Newtok. In addition, due to persistent southerly to southwest winds up Kuskokwim Bay, a River Flood Watch has been issued along the Kuskokwim River from Bethel to the mouth of the river Saturday afternoon through Sunday afternoon. The greatest push of southerly winds looks to be Saturday morning into the early afternoon before winds turn more southwesterly during that time, but persist into Sunday night.

.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)...

Models are in loose agreement to start off the long term period on Monday with an upper low south of Kamchatka lifting across the Western Aleutians by Monday afternoon. Previously, operational models had taken this low on a more southerly track with potential for stronger winds across the Aleutian Chain through Tuesday.
More recently, however, the operational models have trended substantially further north, with agreement between the models becoming much poorer. This has resulted in putting more confidence in the ensemble guidance, which has been more consistent and in better agreement keeping the southerly track of the upcoming low.
What this means is a continued active pattern for the Bering and Southwest Alaska with above normal precipitation chances expected and potential for elevated winds as a low and its attendant front span the entire west domain.

Conditions will be somewhat quieter to start off the long term period for Southcentral. A trough over interior Alaska should be in the process of departing to the northeast with brief high pressure setting into Southcentral on Monday. However, ensemble guidance brings the previously mentioned Bering low and its attendant front into Southcentral by late Tuesday with increasing precipitation chances. These precipitation chances look to linger through the second half of next week with seasonably normal temperatures for the region.

BL

AVIATION

PANC...A very moist air mass with generally light low level flow will lead to a mixed bag of ceilings across the Anchorage area.
This leads to quite a bit of uncertainty in prevailing ceiling heights at any given time. Largely think MVFR conditions will prevail, with occasional IFR. As the rainfall ends late tonight/early Friday, conditions become favorable for fog formation. Light northwest flow favors Knik Arm and the front range Chugach for lower conditions. Have gone VFR for now at the terminal, but it isn't out the realm of possibilities that IFR could briefly move in Friday morning.

-JR/SEB