textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages:

- Hot and dry conditions today through Sunday morning then a shift back to cooler and wetter for a good portion of Southcentral for early next week.

- Heat Advisory remains in effect for the Copper River Valley through this evening.

- Flood Watch now in effect for the eastern Kenai Peninsula from Monday night through Thursday morning, due to heavy rain.

- Flood Watch remains in effect for Susitna and lower Matanuska Valleys from Tuesday morning through Friday morning, due to heavy rain.

Discussion:

Today will be the last hot and dry day for many locations across Southcentral as the pattern shifts back to cool, wet, and cloudy by Monday and Tuesday. The stout ridge of high pressure that brought the hot and dry conditions has shifted east with ridge axis over the Copper Basin and ALCAN border. While still on the warmer side, western Southcentral will see cooler temperatures as cloud cover begins to increase today ahead of the incoming system. Being further east, the Copper Basin will still see abundant sunshine that will allow the lower elevations and river valleys to once again near 80 degrees this afternoon. Winds will initially start out light, but will strengthen this afternoon as the gradient over the Chugach Mountains tightens. The gusty winds combined with the warm conditions and lower relative humidity values will increase fire weather concerns for the valley; however, expect the southerly flow to start advecting more moisture into the Basin later this evening. The Turnagain Arm and Knik winds will also increase this evening, remaining gusty through Monday. The current forecast calls for gusts approaching 60 mph for the Anchorage/Eagle River Hillsides, and approaching 45 mph for lower elevations of Anchorage/Eagle River and Copper River Valley.

THe system responsible for this shift back to a wetter pattern is currently taking shape over the western Bering Sea. Overnight the next 24 hrs, the upper low transit east towards the western Alaska coast. This system has tapped in to a modest plume of subtropical moisture over the North Pacific. This stream of moisture will move up into Southwest Alaska, spreading north into inland Alaska and pushing east. Satellite-observed precipitable water (PWAT) values are reaching as high as 2 to 2.5 inches, and models are placing PWAT values in the 1 to 2 inch range. Regardless, this is a juicy system that will bring a period of moderate to heavy rain beginning late Monday and continuing through at least midweek. The Susitna Valley will see another of rainfall totaling 2.5 to 5 inches, which will allow river levels to once again increase with crests likely occurring Wednesday or Wednesday night.

Moderate to heavy rainfall is also anticipated across the eastern Kenai Peninsula with rainfall totals of 2 to 4 inches possible in Seward as favorable southerly flow establishes for a good portion of the event. Flooding concerns remain marginal for Seward and surrounding areas, but could see river levels rise and ponding in low spots.

- PP

AVIATION

PANC...VFR conditions will likely prevail through the TAF period. However, another southerly push of maritime air is expected to bring fog/low stratus up the Cook Inlet this morning. While this marine stratus will likely remain to the west of the terminal, there is a slight chance it pushes into the airport. If this occurs, it could bring IFR ceilings and visibility reductions for a brief period. Light westerly winds will shift southeasterly and intensify by the late afternoon/early evening as a Turnagain Arm wind develops. Winds will steadily increase through the evening/overnight hours, with gusts to 30 kts possible by tomorrow morning.