textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

A weakening low near Kodiak remains relatively stationary as it continues dissipating over the next 24 hours. Several shortwaves embedded within a much more robust trough move across Southcentral Alaska today through Wednesday afternoon. The more stable atmosphere will allow for a more steady rainfall across much of the Susitna Valley and Copper River Basin, as well as along the north Gulf coast over the next couple of days. Periods of moderate to heavy rain will be prominent with the passing of the waves along the northern and western Susitna Valley today and tonight with lighter rain for Wednesday. Skwentna, Talkeetna/Trapper Creek and north through Broad Pass up to Cantwell will see between 1 and 2 inches of rainfall. Upslope enhancement will promote higher rainfall amounts farther inland, near the Talkeetna Mountains and the Alaska Range. Lower elevations (including Anchorage) will see less rainfall due to downsloping, but the sheer amount of moisture making it in will allow at least 0.05 to 0.10 inches of rain to fall. Chances for rain decrease by late this afternoon below 30% for much of the Copper River Basin and north Gulf coast, though some light rain showers may linger along the Kenai Mountains north to Whittier through tonight. These conditions carry over into Wednesday, with rain chances isolated to the Wrangell Mountains. Thursday will see moisture move back into the Copper River Basin. This, combined with continued easterly waves will allow chances (50 to 60%) for showers.

KM/JR

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

The long-term pattern continues to feature an unsettled pattern across the Southern Mainland. A low pressure system in the Bering Sea will continue to bring showery conditions across the Central Aleutians, Eastern Aleutians, and Pribilof Islands Friday and Saturday before the rain moves to the Southern Alaska Peninsula (AKPEN) for Sunday. A ridge builds in behind this system with likely low stratus and misty conditions filling in across the central Bering Sea and Central Aleutians Saturday evening into Sunday. This ridge and the associated low stratus will move eastward through Monday across the rest of the Aleutians and Southern AKPEN while the Western Aleutians and western Bering will contend with North Pacific fronts.

Southcentral and Southwest Alaska will also remain unsettled as a series of easterly waves moves across the Southern Mainland from Yukon, Canada and shortwaves lift from the North Pacific, the the Gulf of Alaska, and over Southcentral Alaska. Most steady precipitation with these disturbances between Friday and Monday will look to fall across interior portions of the Southwest Alaska with scattered rain showers across Southcentral Alaska. The one challenge with the long-term forecast, with regards to the interior locations, will be assessing how much instability will be available. This will determine how much of a threat lightning strikes could become. Right now, Friday afternoon looks to be the most unstable day across Southwest Alaska with Sunday afternoon across the Copper River Basin of Southcentral Alaska.

AVIATION

PANC...VFR conditions are expected to persist. A Gulf low is expected to bring sufficient moisture along terrain to produce showers tomorrow afternoon. Southeasterly Turnagain Arm winds will pick up again this afternoon, with gusts reaching up to 25 kts.

FIRE WEATHER

Key Message:

Wetting rain chances increase for Tuesday and Wednesday across interior Southcentral Alaska and interior Southwest Alaska.

Discussion:

A strong easterly to southeasterly shortwave will lift across the Gulf of Alaska through Monday night and spread wetting rains beginning Tuesday morning across the Copper River Basin. The airmass this upper-level disturbance is moving over will be stable, so lightning should be little threat. Steady wetting rains will move to the Susitna Valley by late Tuesday morning. Wetting rains then shift to interior Southwest Alaska by Tuesday afternoon to Tuesday evening with areas along the Western Alaska Range as well as Port Alsworth and northward seeing steady rain. This steady rain will last across interior Southwest Alaska will last through Wednesday morning before tapering off. Southeast flow behind the upper-level disturbance, now over Southwest Alaska by Wednesday afternoon, will allow for more moisture to be rung out across the Western Susitna Valley along the Alaska Range through Wednesday evening which will result in more wetting rain for that area.