textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Discussion:

Satellite imagery this afternoon shows the stacked low out in the Gulf is starting to dip southwards as the surface low weakens and eventually merges with a new surface low that is currently developing further east. As the new surface low becomes more established, the upper low will move out into the central Gulf where is will wobble around while slowly moving eastwards towards the Southeast AK coastline by Tuesday evening. This system brought abundant cloud cover to Southcentral with widespread rain mainly confined to the northern Gulf coast, including the eastern Kenai Peninsula and Prince William Sound. More scattered showers were found inland for the Copper Basin westward to the Mat-Su as the easterly wave pushed westwards. Convective showers should taper off later this evening as diurnal heating ends and the wave moves out of the region.

As the Gulf low pulls away from the western Gulf, clouds will begin to clear out as shortwave ridging begins to build in from the west. This will allow for a warmer day for most of Southcentral both tomorrow and again on Tuesday. Monday continues to look more active as northeasterly flow develops across Southcentral in between the low and a building ridge to the north over the Interior. This will help drag a much warmer and a more unstable airmass south into the region, supporting a more significant threat for afternoon thunderstorms. An easterly wave rotating across the Chugach Mountains around the north side of the low will provide extra lift and forcing to help initiate convection. This feature will also provide enhanced easterly flow and up to 25 kts of deep layer wind shear, enough to support some slightly more organized storm clusters that should initially develop over and near the Talkeetna Mountains. Steering flow will easily be strong enough to pull initial storm clusters west into the Mat-Su Valleys during the afternoon and evening. Even Anchorage will have a chance (around 20-30%) to see a thunderstorm moving off of the Hillside into lower elevations during the late afternoon and evening hours.

By Tuesday, Southcentral will shift back into a col (a gap in between larger weather systems) along with much weaker winds aloft. Showers and isolated thunderstorms will again be possible during the afternoon and evening, especially along and near the various mountain ranges. The northern Susitna Valley and Talkeetnas will again have the best shot at seeing lighting activity. Otherwise, expect another very warm day afternoon in the upper 60s to mid 70s across the interior valleys.

-AS/PP

AVIATION

PANC...VFR conditions are expected to continue through the TAF period. Turnagain Arm winds are expected to kick in again by late afternoon though they will not be as strong as yesterday, with southeasterly gusts up to 20 kts. These Turnagain winds will diminish through the overnight hours with southwesterly winds expected for the daytime hours Monday.