textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Two distinct shortwaves are rotating around an upper-level low centered over the Alaska Panhandle this morning. The first of these waves is moving over the Copper River Basin and is spreading mid-level clouds over the eastern half of Southcentral along with a few isolated showers over the Susitna Valley. The second, more potent shortwave is near Yakutat this morning and is bringing rain showers to the coast near Cordova. This feature will be the one to bring steadier showers across Southcentral from east to west through the day.

Thunderstorm potential over the Copper River Basin looks a bit diminished from yesterday, due in part to the lingering cloud cover from the first shortwave trough moving through the region this morning. A distinct band of cloud cover and moisture is also associated with the second wave, with both helping to keep temperatures a bit cooler and the airmass a bit more stable over the Basin today. Farther west, clouds should scattered out between these two features, allowing for additional daytime heating and better instability. As such, isolated to widely scattered thunderstorms are again possible across the Susitna Valley. A few thunderstorms will also be possible along the foothills of the Kenai and western Chugach Mountains.

As this wave moves west through the Copper River Basin today, it will run into yet another wave, associated with a surface front, moving east from Southwest Alaska. As this wave digs across Kennedy Entrance, it will pull moisture from the other as winds aloft become more southeasterly. This will allow showers to overspread Cook Inlet, Anchorage Bowl, and Mat-Su Valleys late tonight through early Wednesday morning. a new surface low will then spin up along the front and get pulled southeast into the southern Gulf. The residual Copper River trough will then elongate and get pulled southward through the day Wednesday with scattered showers redeveloping over the higher terrain drifting east over Anchorage and Cook Inlet in the east-northeast flow aloft.

One other item of note will be the development of strong southeasterly gap winds for Turnagain Arm, Knik River Valley, and Copper River Valley this afternoon through late tonight with gusts up to 35 mph possible.

-TM

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

An upper-level ridge centered over the ALCAN will remain the dominant synoptic feature through much of the long-term period, supporting generally warmer conditions across mainland Alaska. While the ridge promotes periods of sunshine, several weak shortwaves rounding the ridge will keep the potential for scattered showers across portions of Southcentral through the weekend. The greatest chance for convective development will remain over the eastern Copper River Basin, where daytime heating combined with passing disturbances may support isolated to scattered afternoon and evening thunderstorms Friday through Sunday. Elsewhere across Southcentral, precipitation will be more limited.

Across the Bering Sea and Aleutians, an active pattern persists as a series of lows track eastward through the weekend, bringing periods of rain, low clouds, and locally gusty winds. Forecast confidence in the exact track and timing of these systems remains moderate, though the highest confidence for more persistent rainfall continues to be from Adak eastward to Unalaska.

Attention then turns to a stronger North Pacific low expected to move into the western and central Bering over the weekend before lifting toward Bristol Bay late Sunday into Monday. As the system approaches, widespread rain will overspread much of Southwest Alaska with increasing winds, especially along the Alaska Peninsula and Bristol Bay coast.

By Monday, the low is expected to continue tracking inland while gradually weakening, allowing rain to spread farther across the Kuskokwim Valley and portions of interior Southwest Alaska. Meanwhile, Southcentral Alaska will remain on the eastern periphery of the system beneath the upper-level ridge, supporting isolated showers over the higher terrain while lower elevation may experience a mix of clouds and sunshine. Although model spread increases by Monday regarding the exact evolution of the low, confidence is growing in a wetter pattern across Southwest Alaska.

AVIATION

PANC...VFR conditions will likely persist through the TAF period. Winds will be light and variable through the early afternoon. By the mid to late afternoon a Turnagain Arm wind will redevelop and bring southeasterly gusts up to 30 kts. Through the late afternoon/evening a shower in the vicinity of the terminal is possible; however, downslope winds should stave off most showers. Turnagain winds will gradually weaken through the overnight and evening hours, but some gusty winds may linger through tomorrow morning. Showers will likely develop over the terminal by late tonight and linger into early Wednesday morning.