textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

The overall general pattern of a nearly stationary, vertically stacked low is anchored in the Gulf of Alaska. Its shortwave extending from this low remains near the Yukon and is rotating westward through the Copper River Basin. Showers under northerly flow are on-going this morning across the Wrangell Mountains, southeastern Copper River Basin, and the Valdez-Cordova area.

The potential for showers and isolated thunderstorms will return this afternoon along with sea breezes near the coast. A coastal ridge will develop today that will allow for southerly gap winds to develop through Turnagain Arm, Copper River, Knik River, and other southerly valley/terrain gaps.

Although there is more convective potential today than there was yesterday, limiting factors for thunderstorm development would be from increased cloud cover that would limit surface heating and its ability to destabilize the atmosphere over the southern tier of Southcentral. Second, the upper level features are quite complex, with a plethora of shortwaves and vorticity maxima moving through a short-wave ridge. Continued northerly flow across the Alaska Range will lead to more unstable conditions over interior Southcentral, especially across the northern Susitna Valley and Talkeetna Mountains. The complexity of the set-up makes it difficult to pinpoint areas of convective initiation. Based on overall level of instability (and taking into account climatology preferred areas for initiation) the most likely areas for convection are the northern portions of the Susitna Valley and Copper Basin as well as the Talkeetna Mountains southward to the Front Range Chugach near Anchorage. Simple advection could cause some of these to move over populated areas of the Matanuska Valley and Anchorage. Thunderstorm potential is higher over the interior then southward across the Talkeetna Mountains to the Mat Valley.

As we head to the weekend, the weak upper level shortwave ridge will sit overhead while a weak shortwave drops southward from the Interior and stalls along/near the Alaska Range. It's looking increasingly likely that moisture will be trapped beneath the ridge and lead to mostly cloudy skies over the weekend (with just an occasional break of sun). A loss of northerly flow will lead to a slight cooling of the airmass and more stable conditions. This will lead to lower coverage of showers and generally lighter rainfall within any showers. Increasing southerly flow up Cook Inlet will keep the population centers dry (or mostly dry). The cloud cover and coolish airmass means temperatures will max out in the 50s for most areas.

Lastly, it is worth highlighting that much warmer and sunnier weather remains on track for next week.

-SEB/Rux

LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)

A high pressure ridge will dominate across the Bering Sea and extend into the western mainland Alaska Wednesday through Saturday, keeping conditions generally stable and dry over Western Alaska, the Aleutian Islands and the Bering Sea. Marine activity should remain fairly quiet under this setup, with little chance of widespread precipitation or significant weather impacts in those far western zones.

Meanwhile, a broad upper level low will stay anchored well south over the southern Gulf of Alaska, limiting any deep moisture reach into Southcentral coastal areas. Expect only light or isolated showers at times rather than heavier or organized rainfall along the Southcentral coast from the Alaska Peninsula through the Kenai Peninsula and Prince William Sound region. Overall the pattern points to a relatively quiet stretch of weather across Southcentral and Western Alaska, with no major precipitation events or hazards highlighted through the weekend.

-DD

AVIATION

PANC...VFR expected. Southeasterly Turnagain Arm winds will return by late this afternoon lasting through tonight with gusts up to 25 kt. A chance for showers will also be possible this afternoon. Low confidence that a ceiling between 3,500 and 5,000 ft could develop Saturday morning as low-level moisture remains and the atmosphere stabilizes.