textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Key Messages:

- Mostly clear skies through this afternoon/evening, then rain and winds return as a low pressure system moves across Southcentral through Saturday afternoon.

- For Susitna Valley, 48-hour rain totals around 0.5 to 1.5 inches will allow for rises on many small streams and rivers, and localized ponding in low-lying or poor drainage areas.

- Winds pick through Cook Inlet and along Prince William Sound by late Thursday, with localized gusty southeasterly gap winds through Anchorage and Copper River Valley.

Discussion:

A shortwave trough that brought rain showers overnight to the Copper Basin is exiting to the east this morning with clearing of clouds allowing for pockets of fog to develop along the river valleys. Fog and low stratus will begin to mix out by mid-morning with generally clear skies and warm temperatures this afternoon. The rest of Southcentral has remained mostly clear overnight, but any hint of fog developing in the known trouble spots has been lacking as of 4am this morning, with the exception of Cordova where patchy fog has developed. Any fog that does develop in these other locations will also mix out by mid to late morning.

Near normal temperatures today and mostly clear skies will make for a beautiful morning and early afternoon. Cloud cover will begin to increase from west to east as the next advertised system starts to approach Southcentral. This system, which is currently way out in the Bering Sea near Kamchatka, will push a warm front across Southwest this morning then into Southcentral by this afternoon. The cold front looks to quickly overtake the warm front by late afternoon into this evening. Widespread rain will spread into Southcentral tonight...first into the western Susitna Valley, but quickly pushing into the Cook Inlet, Mat-Su, Kodiak, and Kenai Peninsula. The heaviest rainfall looks to fall tonight before tapering off to more showery Friday morning. A secondary trough and associated front will reinvigorate more robust rain showers Friday afternoon. This system, like the previous system, is fairly progressive and will quickly move through...helping to minimize some of the flood concerns. However, with river levels still high from our rain earlier this week, parts of Susitna Valley will likely see minor impacts as the watershed absorbs this additional rainfall.

This system will also bring another round of gusty gap flow winds for the Turnagain Arm, Knik, and Copper Valley. Similar to the Tuesday, winds with gusts up to 45 mph are possible for west Anchorage and the Hillside. The western Gulf will see small craft to gales move in behind the front and the development of a barrier jet will allow for some gales along the northern Gulf coast. These strong winds will likely push inland some bringing gusty winds to Cordova Friday night.

- PP

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

The progressive pattern looks to continue into early next week as multiple systems move through Southern Alaska. This will generally bring periods of active weather, with some lulls between systems.

Troughing exits Southcentral early Sunday morning with the surface low moving into the northern Gulf. This will increase northwesterly winds through the Barren Islands and around Kodiak Island/the AKPen to small-craft force Sunday into Monday. A shortwave ridge moves through Southern Alaska on Sunday. A few shortwaves may ride the periphery of the ridge, which may induce isolated to scattered showers in higher elevations of Southwest and Southcentral, otherwise Sunday looks to be mostly calm inland. By Sunday evening, an Arctic low dives south into the western interior. This low continues southeastward through Southcentral and into the Alaska Panhandle by Wednesday. Models diverge with exact timing but agree on features with this low. As the low moves south, temperatures will cool. This will especially be the case for Southwest as many locations may struggle to get above the mid 50s Monday-Wednesday. Lowest elevations of Southcentral will be slightly warmer, though likely struggle to reach 60. Scattered showers will continue to across eastern portions of Southwest and much of Southcentral as the upper low passes through. Cooler temperatures will drop snow levels to around 4000-5000 ft. Some termination dust (snowfall) may be seen on the highest peaks of the Chugach Front Range and Kenai Mountains, as well as some lower portions of the Alaska Range by the middle of next week. A surface low looks to develop in the Gulf Monday into Tuesday and maintain small- craft northwesterly winds around Kodiak Island, the AKPen, and through the Barren Islands into the Gulf through Wednesday morning.

For the southern AKPen, the Aleutians, and the Bering, most models agree with a flat ridge persisting overhead through Tuesday, but diverge on surface features below. Some precipitation looks likely Monday- Tuesday in the AKPen as northwest winds upslope against the mountains. Other than that, there are major differences between models regarding potential systems moving into the Bering. Even with these differences, areas of rain and small- craft winds are possible throughout the Bering and Aleutians through Wednesday. If a system is able to track through the Bering and reach the coast, Southwest may receive additional rainfall Tuesday into Wednesday. Details will become more clear in the coming days.

- PA

AVIATION

PANC...VFR conditions and light winds will persist. While patchy fog near the airport early this morning cannot be fully ruled out, it looks unlikely at this time. Rain will spread into the terminal tonight with Turnagain Arm winds increasing Friday morning with gusts up to 45 kt.