textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Discussion:

The near-term forecast remains on track with a band of snow extending from about Kenai northward through the Anchorage Bowl and up through the Mat-Su Valley slowly pivoting westward. This band produced several inches of snowfall with snowfall rates of about a half inch per hour overnight. This band may weaken somewhat this morning before being reinvigorated later today.

The larger scale synoptic pattern shows that a trough remains draped along the western Alaska Range with the parent Arctic low progged to quickly drop southwest from the North Slope towards the Seward Peninsula then into the northern Bering Sea by early Wednesday morning. On the Gulf side, satellite imagery shows a deepening low lifting north across the Gulf. It will be this system lifting up towards Prince William Sound that will bring the next round of moderate to heavy snowfall first to the higher elevations around Prince William Sound and the eastern Kenai Peninsula then spreading into the western Kenai, Anchorage Bowl, and Mat-Su Valley by mid to late morning. It is still looking good for a period of higher snowfall rates of 1-2" per hour for several hours this afternoon before the system starts to wind down. Forecast snowfall totals remain on track through Tuesday evening but could be tweaked once the heavier snow band sets up. Heavier amounts of up to 2 feet in total are still expected for Valdez and Thompson Pass through late Tuesday. Storm total amounts of up to 18 inches remain on track for the Copper Basin. Snow will finally come to an end from east to west on Tuesday night.

For Wednesday and beyond, a warmer and still unsettled pattern will continue for much of Southcentral. A potent trough will move across the Gulf from east to west on Wednesday, sending a corridor of gale force winds across the northern Gulf and another round of precipitation into Prince William Sound and the eastern Kenai Peninsula. This feature will also bring a surge of warmer air in from the southeast, changing snow over to rain near sea level along the Gulf coast. Farther inland, temperatures at the surface will remain below freezing at ground level. While little precipitation is expected to make it past the coastal mountains, anything that does spill over into the Mat Valley, Anchorage or western Kenai Peninsula could fall as freezing rain or sleet due to the warm intrusion aloft. By Thursday, a gale force low will move into the Gulf, extending a period of gusty winds and rough seas along with periods of rain/snow along the Gulf coast.

- PP/AS

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

The long term forecast for both Southcentral and Southwest Alaska is characterized by an active pattern. Many upper level features will make their way into Alaska from the North Pacific, which will bring a mix of weather from snow, rain, and winds.

For Southcentral, these upper level features will stream into the Gulf of Alaska through the weekend. The Gulf Coast is likely to see periods of precipitation as these features push inland. Due to a warmer air mass from southerly flow, rain or a rain/snow mix is the likely precipitation type for these waves. Any precipitation that makes it further inland will likely be snow. A larger low looks to move into the Gulf of Alaska on Sunday, likely bringing gusty winds and precipitation to the Gulf Coast and Kodiak Island.

Southwest Alaska will be a little different. Cold air advection due to northeasterly flow will continue through the weekend, interacting with weak features to produce areas of snowfall in the Bering and the Southwest Mainland through the weekend.for snow showers in the Bering and more constant snow in the Eastern Aleutians. Uncertainty with the pattern arises on Monday with the large low in the Gulf of Alaska potentially sending shortwaves to Western Alaska and advecting warmer air. This could cause a mix of rain and snow for the Aleutians by Monday.

-JAR

AVIATION

PANC...Moderate snowfall with MVFR ceilings and IFR visibility may give way to a lull with lighter precipitation this morning before the heaviest precipitation of this event arrives this afternoon. During the lull, cigs/vsby may lift to MVFR or even VFR for a short time. The heavier snow this evening will drop cigs/vsby back to IFR or LIFR through the evening. Snow will end rather abruptly around or shortly before midnight, allowing ceilings and visibility to turn VFR and remain so through Wednesday. These changes may be accompanied by the development of a weak, brief Turnagain Arm wind that shifts light northerly winds to gusty variable/southeast winds up to 20 kts. If this change occurs, light northerly winds are expected to return by 15Z.

Quesada