textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages:

- Special Weather Statement for strong winds in Anchorage, Anchorage Hillside, and Mat-Su through 7 PM this evening.

- Rainfall today and Friday in the Susitna Valley will allow for rises on many small streams and rivers, and localized ponding in low- lying or poor drainage areas.

Discussion:

Currently, a shortwave continues to sweep across mainland Alaska and has brought widespread showers across much of Southcentral. A surface low currently positioned in the Cook Inlet has ramped up southeast winds, especially through gaps like Turnagain Arm and the Copper Valley. Throughout the evening, both the shortwave and the surface low move into the Gulf. Precipitation will slowly taper off overnight into tomorrow morning, first in the Kenai Peninsula, then Anchorage and Mat-Su, and finally the Copper River Basin tomorrow morning. Southeast gap winds will also weaken overnight as well. Kodiak Island has avoided much of the rain and will continue to do so tonight.

With the low in the Gulf by tomorrow morning and continuing eastward, the weather will be mostly benign across Southcentral tomorrow and Thursday as zonal to northwest flow takes shape overhead. The low in the gulf will enhance northwest winds to small-craft through the Barren Islands tomorrow. Additionally, a shortwave moves through the Upper Susitna Valley and Wrangell Mountains tomorrow through Thursday morning, which may bring some scattered showers tomorrow afternoon and evening. Otherwise, most of southcentral will be calm and dry underneath partly cloudy skies.

Cloud cover increases Thursday afternoon and evening from west to east as the next system approaches from the Bering. Widespread precipitation will spill over the Alaska Range into Kodiak Island and western Southcentral late Thursday night and spread across all of Southcentral on Friday. Precipitation will be heaviest along the northern Gulf Coast into the Chugach Mountains. Southwest winds will strengthen in the western Gulf and Shelikof Strait to small-craft by Friday morning. Additionally, a surface low looks to develop in the northern Gulf Friday morning. Depending on the strength of the pressure gradient with the coastal ridge, this will enhance easterly and southeasterly winds Friday, especially in properly aligned gaps (Turnagain Arm, Knik River, and Barrier Jet).

- PA

LONG TERM FORECAST (Days 4 through 7: Saturday through Monday)

The active, progressive pattern continues into early next week as multiple systems track from west to east. This will generally bring periods of active weather, with lulls in between for Southwest and Southcentral Alaska.

By Saturday, a trough will be over much of Alaska. This will likely bring widespread rainfall and elevated winds to coastal and mainland Southcentral and Southwest Alaska. This trough will quickly push eastward and weak ridging/zonal flow will set in, allowing for wind speeds and rainfall to dwindle. The Bering will see a trough with an associated front move in from the west. Sunday will see this front progress eastward, leading to a swath of rainfall and gusty winds across the Aleutians. However, the exact intensity and path of this weather is uncertain as of now. For Southcentral, ridging will continue, with lighter winds and clearer skies.

Uncertainty increases on Monday as a low moves into the Bering. The exact track of it cannot be determined at this point, but gusty winds and rainfall will likely arise somewhere along the Aleutians. A plume of moisture riding up and around a ridge in the North Pacific will lead to heavier rainfall with this low. Again, the exact rainfall amounts will depend on the track of the low moving into the Bering. Southcentral will have a low move into the Gulf of Alaska. Once again, there is much uncertainty with wind speeds and rainfall intensity with them being highly dependent on how strong the low is.

-JAR

AVIATION

PANC...The strong southeasterly winds gusting 30 to 40 kts will continue through the afternoon and then taper off throughout the evening. This drop in winds will likely happen rapidly after the front passes through the area from the west. Rainfall will also persist until the front passes. In spite of the rain, the strong winds are likely to keep visibility in VFR range and ceilings just dipping to MVFR levels.

By midnight, winds should have tapered off and any lingering showers ended. The only real question after that is whether there will be any development of low clouds or fog for the early morning hours. This is heavily dependent on skies clearing enough behind the front as well as winds becoming nearly calm. No model guidance is showing fog or stratus so am just keeping a few lower clouds in the TAF for now.