textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Discussion:

Periods of moderate to heavy rainfall along the immediate northern Gulf coast and eastern Kenai Peninsula will slowly trend lighter this afternoon into this evening, as the vertically stacked low in the southwestern Gulf slowly drifts east and onshore flow weakens. Within the broad longwave troughing stretching from the Bering Sea across the Gulf, shortwaves embedded in the flow rotate inland allowing for periods of light rain to spill over the mountains at times. The western Kenai up through Anchorage and the MatSu, as well as the southern Copper Basin, could see up to a tenth or two of light rain through this evening. Periods of snow will be possible at higher elevations with snow levels fluctuating between 2500 ft to 4000 ft along the Kenai and Chugach Mountains. The strongest of such waves should clear the region by late tonight with lighter, more showery precipitation lingering along the coast through Friday as the low weakens and tracks east across the central Gulf. Gusty winds through favored gaps, along the coast, and within Prince William Sound weaken to small craft or below through this evening in the wake of the wave pushing inland.

The upper trough slowly translates eastwards towards the Panhandle through the remainder of the weekend, with drier conditions expected across Southcentral as weak, transient ridging moves over the region. Temperatures trend cooler through the weekend, with temperatures well below freezing across the Copper Basin and near or just below freezing across the Kenai Peninsula, Anchorage, and the MatSu by Saturday night and Sunday morning.

LONG TERM FORECAST (Days 4 through 7, Monday through Thursday)

By Monday morning, there is fair confidence (60 to 70%) for a low pressure system, with a depth near 995 mb, to be moving inland into the Kuskokwim Delta, potentially bringing strong onshore winds and wave action to the coast. Given southerly flow continuing to bring in warmer air, rainfall is expected with this system. Additionally, the front of this low is set to break off into a triple-point low spinning up in the western Gulf of Alaska by Monday morning, pushing inland to Southcentral through Monday bringing similar conditions to the northern Gulf Coast.

Confidence in increasing with regards to the progression of a stronger low moving into our area south of the Alaska Peninsula by Tuesday morning. By Tuesday morning, this low may be near 960 mb and would work to drive stronger winds along the Alaska Peninsula as well as bring a large swath of rainfall across the area. By Tuesday night/Wednesday morning moderate model agreement suggests the progression of this low pressure system into the northern Gulf of Alaska bringing it's round of active weather to the Southcentral coastline. There is poor model agreement regarding the progression of the low beyond Wednesday, with several solutions weakening the low in the northern Gulf, while others hold on to it's strength. However, generally unsettled weather expected for the region through the long-term period.

AVIATION

PANC...A series of upper level short-waves will rotate from the Gulf up across Anchorage this evening, which could bring an occasional short period of light rain. With deep southeasterly flow aloft VFR conditions will persist. Meanwhile, northerly winds will shift to southeasterly off of Turnagain Arm between 03Z and 06Z. The strongest winds will remain out over Turnagain Arm and stable air near the surface is not conducive to producing gusty conditions. With that said, there is a chance (30-40%) of a few wind gusts at the terminal in the 12-20 kt range this evening.