textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Message:

* Thunderstorms will develop this afternoon many places across Southcentral today. In the strongest storms, be aware of frequent lightning, small hail, and brief heavy downpours that could cause localized flooding. If you hear thunder or see lightning, seek shelter.

* A Red Flag Warning has been issued for LIGHTNING for the Southern, Central, Western, and Northern Susitna Valley, and the Lower Matanuska Valley from 1PM AKDT this afternoon to 1AM AKDT Saturday.

Discussion:

High pressure spans across Southcentral and eastern portions of the state while low pressure draped across the western portions of the state including Southwest Alaska and the eastern Bering Sea. Easterly waves rounding the ridge had a northeast to southwest trajectory yesterday and now they are beginning to pivot west and northwestward this morning. These waves will continue to lift northwestward today toward Cook Inlet and the Susitna Valley. Some of these easterly waves will cross the western Alaska Range into the Kuskokwim Valley, where it will interact with the trough out west.

With high temperatures warming well into the upper 70s and stronger upper level forcing, widely scattered to scattered thunderstorms will kick off this afternoon through this evening. Although there will be plenty of rainfall with brief, heavy downpours, ample cloud to ground lightning strikes in the vicinity of the storms pose the threat of new fire starts. As we lose daytime heating late this evening and early Saturday morning, any remaining storms will weaken into rain showers.

Upper level energy rotating around the ridge axis will continue through Saturday afternoon. The track of another shortwave lifting out of the Gulf into Southcentral is better as it approaches the coast, but differences still remain, especially as the trough tracks inland. Storm coverage for Saturday is will not as prevalent when compared to today, but isolated chances appears most likely for the Copper River Basin and portions of the Susitna Valley.

By Sunday morning, there is fair agreement among the global models of a relatively weak area of low pressure entering the western Gulf, which has the potential to bring rainfall to Kodiak Island. Winds across the Gulf have been southwesterly and will shift southeasterly for Sunday and Monday. Precipitation associated with the low will lift north across the Gulf, but models differ with how much progression it will have before weakening.

-Rux/AM

AVIATION

PANC...VFR conditions and light winds will persist. There is a chance of showers, and potential thunderstorm activity in the vicinity of the terminal this afternoon and evening.