textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Points:

* Unseasonably wet and windy weather is on the way for Wednesday through Friday.

* The wettest weather will be the eastern Kenai Peninsula, Prince William Sound, and the Susitna Valley with rainfall totals of 1 to 3 inches expected for most communities. Portage and Cordova may see up to 4 inches or rain.

* Strong and gusty southeasterly gap winds will develop Wednesday and persist through at least Thursday, with the first peak of strongest gap winds likely late this evening into early morning Thursday. Locations that will see some of the strongest winds include Turnagain Arm, Anchorage Hillside, south to west Anchorage, Palmer and the Knik River Valley, and Glennallen and the Copper River.

The overall forecast is on track, with only minimal changes overnight. These changes include an increase in magnitude of peak wind gusts tonight for locations such as Anchorage, Palmer, and Glennallen; a slight shift west in the track of the low moving into the western Gulf and Cook Inlet for late Thursday into Friday, and a slight increase in rainfall amounts for a few coastal locations, especially Cordova, Portage, and Seward.

A large and deep vertically stacked low remains nearly stationary over the southern Bering Sea. A strong short-wave lifting northward along the eastern side of the trough is leading to amplification of a downstream ridge, which extends across the mainland. An atmospheric river extends from the tropical Pacific northward to the Bering Sea low. While total precipitation values are not all that impressive at less than 1 inch, this is the driest time of year for Alaska and these values are 200% to 285% of normal for the time of year. A frontal system is spreading out from the low center across the northern and eastern Bering Sea. A weak warm front continues to move northeast across the western Gulf, with a general increase in cloud cover along with a band of light precipitation moving across Cook Inlet and Prince William Sound, Much of this precipitation is not reaching the ground as of 4 am, due to drier air near the surface aided in part by weak southeasterly gap winds through typical locations.

On Wednesday, we will establish the large scale pattern that will hold through the remainder of the week. The upper level flow will continue to amplify and shift eastward, with the ridge ultimately setting up shop over the eastern Gulf northward to the Yukon. This will establish deep southerly flow and moisture transport from the north-central Pacific to Southcentral. Multiple short-waves will track from south to north through the week and combine with strong low level southerly upslope flow to produce widespread significant rainfall for coastal areas as well as the Susitna Valley. There is some model spread in the track and amplitude of individual short- waves which could shift the area of heaviest precipitation. However, no matter the track of individual short-waves, the eastern Kenai Peninsula and Prince William Sound regions will see the brunt of precipitation and winds. Precipitation will fall as all rain at sea level, with snow levels ranging from roughly 1500 to 3000 feet above sea level Wednesday through Friday. There seems to be enough shifting of the location of heaviest rain as short- waves and surface fronts move through, so no one location sits in the heavy rain for too long. Based on this, do not expect any flooding. However, will continue to monitor changes in model guidance to ensure this doesn't change. Inland areas from the western kenai to Anchorage, the Matanuska Valley, and the Copper River Valley will see some downslope flow, which will limit rainfall duration and amounts.

-SEB/TM

AVIATION

PANC...Winds this morning will be out of the southeast and generally remain light, ocassionally gusting to 25 mph. VFR conditions are expected to persist through most the period, with a slight chance conditions briefly dip to MVFR with any passing rain showers, particularly this morning. Turnagain Arm winds will increase through the day and remain active, with downslope flow helping keep most showers out of Anchorage by this afternoon and into the evening. However, a slight chance of showers moving over the terminal remains.