textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Discussion:

An upper-level ridge axis extends from south of the AKPen northeast over the northern Copper River Basin this morning. At the surface, an area of cold high pressure sits over interior Alaska with a tandem of compact surface lows over the Gulf of Alaska. A fairly tight pressure gradient between the two is keeping northerly gap winds in place along the coast, especially for Seward and the waterways south of Valdez. There remains high confidence that these winds diminish through the late morning hours as the areas of low pressure drift farther south and weaken.

With high pressure in place, overnight low temperatures have dropped into the teens and 20s for most locations, with even a few locations in the northern Copper River Basin in the single digits to around zero degrees. An area of low stratus clouds remains over much of the Copper River Basin, expanding northward as the air near the surface cools and saturates. This area of cloud cover will remain trapped underneath the ridge this morning, but will likely erode by early afternoon as temperatures warm and the upper-level ridge axis shifts south of the region.

This will likely be the coldest morning as there is good model agreement that clouds will be on the increase from west to east later today in response to a strong frontal system moving east from the eastern Bering today.

Beginning Saturday afternoon, the front of a strong Bering low will increase chances for rain across Kodiak and the southeastern Kenai Peninsula and by Saturday evening across the far western Susitna Valley. Chances for rain overnight from Saturday to Sunday range from 45 to 60% for the Anchorage Bowl and Palmer, and up to 70 to 90% for the Gulf coast, Homer, and the Susitna Valley. Most locations closer to the coast will see rain, or a slight chance (15-25%) of a rain and snow mix, with this system. However, for locations in the central and northern Susitna Valley and northern Copper River Basin, there is high confidence (80-90%) that precipitation falls mainly in the form of snow with a mix of rain and snow at times. For the Susitna Valley, this includes typically colder locations (e.g. N of Willow and N and W of Talkeetna, including Broad Pass).

As this system moves through, southeasterly gap winds and a southerly flow advecting warmer air aloft will allow daytime temperatures across Southcentral warm back up into the mid 30s to low 40s by Sunday with nighttime lows in the low 30s, with the Copper River Basin dipping to the low 20s and high teens.

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

Discussion:

The long term forecast continues to remain focused on a series of systems that will lift up across the Bering Sea. Forecast confidence has remained fairly steady, with most model solutions showing decent continuity on general placement and timing of these systems riding along on southwesterly flow. Meanwhile, high pressure will take up residence on the Gulf side with ridging in place for much of the week. Several of these aforementioned systems may try to ride up the western periphery of the ridge...helping to flatten it some before it rebuilds over the Gulf. As such, Southcentral looks fairly quiet through midweek with best chances for some precipitation on Monday.

Most of the systems over the Bering will be rotating around a complex Kamchatka low. These systems will swing around the base of the low, moving across the Bering, and lifting up towards the Southwest Alaska coast and Bering Strait area. Strong winds and moderate to heavy precipitation will accompany each of these systems, strongest along the coast then dropping off as the front moves inland. Rain looks to be the primary precipitation type for lower elevations, but some locations across the Kuskokwim Delta / Nunivak Island area down towards the Greater Bristol Bay area could possibly see a changeover to a mix of rain and snow, or all snow at times. One feature to keep an eye on next week will be a strong North Pacific low moving into the western Aleutian Islands and Bering Sea.

- PP

AVIATION

PANC...High pressure over the region will result in VFR conditions and light winds through the TAF period.