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.

* Strong and gusty southeasterly gap winds will develop Wednesday and persist through at least 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.

A large and deep vertically stacked low is 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 is building from Southwest Alaska north and east 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 is lifting northward across Bristol Bay and the western Gulf, with a band of light precipitation noted in radar imagery. For the moment, much of Southcentral is quiet, under mostly sunny skies - but a change back to cloudy, windy, and rainy is on the way.

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

AVIATION

PANC...Gusty winds are expected to become light from the south to southeasterly by this evening. VFR is expected through the rest of the day today. There is a small chance for ceilings to dip into MVFR with a brief shower ahead of the approaching front after midnight tonight. Chances for rain and MVFR ceilings become more likely by 12Z. Southeast winds will increase later Wednesday morning and any potential for downslope drying could help to lighten precipitation and lift those ceilings into VFR Wednesday afternoon. Turnagain Arm winds will increase Tuesday afternoon, initially turning more down inlet then out towards Fire Islands and beginning to bend towards the terminal by Wednesday evening.