textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

Satellite imagery from early this morning shows Southcentral sitting underneath an upper level trough with the remnants of what used to be a significant surface low just east of Kodiak. An area of snowfall is in the western part of Cook Inlet along the weakening frontal boundary. With temperatures just a few degrees below freezing, this is potentially setting up the atmosphere for fog and/or stratus across the Cook Inlet region. All it needs is the slightest clearing and fog will be in a hurry to form this morning. Persistent low clouds and fog may become the main weather story for today into Sunday near Cook Inlet and in the Susitna Valley.

By Sunday there should be a noticeable cooling, drying, and clearing trend for the region as the low continues to move eastward and weak high pressure aloft edges into the area. This general pattern should persist through Monday giving more seasonal temperatures and dry weather.

LONG TERM FORECAST (Days 4 through 7/Tuesday through Friday)

Starting on Tuesday, a vertically stacked low and large cyclonic circulation will be centered south of the Aleutians in a weakening phase. Short-waves embedded within the circulation will track from east to west from the western Gulf/Kodiak Island across the Alaska Peninsula and Bristol Bay and continuing westward across the southern bering Sea. None of the features look particularly strong, so would expect areas of precipitation and wind with typical winter- time impacts. Precipitation-type will be mainly rain, with Bristol Bay being the only location cold enough to see snow. The upper low will open up into a trough by Thursday (Thanksgiving), causing winds and precipitation to diminish.

Meanwhile, a strong ridge in the Arctic will build southward over the northern half of mainland Alaska. This looks far enough south to block any short-waves from the Aleutian trough from reaching interior SW AK or Southcentral AK. Thus, expect seasonably cool and dry conditions for these areas Tuesday through Wednesday. A short-wave will dig down the east side of the ridge on Wednesday, across the Yukon and into the Copper River Basin. This will bring marginally colder temperatures, though accompanying cloud cover will likely limit temperature drops. This trough will force the upper ridge to retreat back northward and allow a short-wave trough to approach Southcentral on Thursday. Model agreement with this feature is not great, but ensembles generally support this idea. With a cold air mass in place over Southcentral, the most likely outcome would be widespread light snow arriving sometime Thanksgiving Day.

As we continue to Friday, model guidance is in excellent agreement on amplification of the upper level flow and development of an Atmospheric River. However, as would be expected this far out in time, there is large spread in the location of the ridge/trough and track of a leading surface low from the Pacific. This evolving pattern does have good potential to bring higher impact weather to southern Alaska, with strong winds, mixed precipitation-types, and warming temperatures. Stay tuned as we monitor the location of key features and identify the areas where the greatest impacts are most likely.

-SEB

AVIATION

PANC...Chances for snow continue to decrease this morning as a low pressure system dissipates. Lingering low-level moisture and a weakening wind flow in the lower half of the atmosphere will likely result in low stratus remaining over the terminal through the late morning, with ceilings expected to rise to VFR levels afterwards. Winds become light and northerly by early Sunday morning, potentially allowing for fog over the Knik Arm to drift over the terminal and cause IFR conditions.