textproduct: Anchorage

SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)

The main tap from the atmospheric river can be seen on Kenai and Middleton Island radars this afternoon with high reflectivities indicative of the moisture content on its way for this storm. Warm air began to intrude into the region this morning, with the Kenai Peninsula, Copper Valley and Mat Valley already in the mid- thirties to 40s. Anchorage and the Susitna Valley have maintained a northwest wind and remained colder, but this will change through the night as strong winds aloft mix down warmer air from Talkeetna south into Anchorage. The most likely area within the abundance of Winter Weather Advisories to receive true freezing rain tonight (rain falling into a cold layer of air) will be from Willow north to Talkeetna, where winds will have a harder time mixing in the warmer temperatures. Elsewhere, rain falling onto frozen and snow covered roadways will be the main ice hazard.

Forecast confidence has increased greatly today with most weather models now in solid agreement. As seen on radar, the abundance of moisture streaming north from Hawaii is already starting to saturate the column, despite strong southeasterly winds. Through the night, winds aloft will transition from southeasterly to more southerly, negating the downsloping effect and allowing for 0.3 to 1.25 inches of liquid equivalent to fall for most of the population centers. Conditions will change quickly tomorrow morning as the cold air rapidly surges back in from the southwest. Strong winds, gusting 40 to 55 mph out of the southwest will bring cold air in to the western Kenai, Anchorage and the Mat Valley, transitioning rain to snow at the tail end of the event. The somewhat rapid refreeze may cause any remaining water on the roads to freeze. The morning commute may be hazardous tomorrow.

For the Copper Basin, warm air has already pushed far to the north, with rain now expected to be the main precipitation type. Rain falling onto snow covered and frozen ground may freeze on impact. Luckily, as far as chinook events go, this one is relatively short in nature, with the system fully out of the region by Friday afternoon. An additional weaker storm will move in on Saturday, bringing light precipitation to the eastern Kenai, Kodiak and the Susitna Valley. This will be another warm system with more details to come.

-CJ

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

A major pattern shift will occur as we head to the extended forecast period on Monday, with an upper level ridge building over mainland Alaska. This will lead to quiet weather for southern AK, a much needed break from the long string of impactful storm systems affecting the area since Christmas. There are some minor model differences with the position of the ridge and handling of weak features along the periphery, but none of those look like they would cause any significant weather. There are signs that the ridge will begin to retrograde westward late in the week, which could bring Arctic air southward across mainland Alaska.

Meanwhile, the Bering Sea and Aleutians will be much more active, with deep storm systems tracking northward from the Pacific across the Aleutians and Bering Sea. This will bring routine doses of warmer air northward, so the main impact will be strong winds and rain with each storm system.

-SEB

AVIATION

PANC...It is a very complex weather situation for this evening into Friday afternoon. The main issues will be wind, wind shear and precipitation type. We start this afternoon with light snow around the airport with VFR conditions. Surface winds should remain northerly up to 10 kt, but the wind shear level is expected to be around 1000 ft above the ground where winds will be southeasterly from 45 to 55 kt through most of the overnight hours. This evening, the precipitation should turn to freezing rain and then to rain and increase in intensity. It looks like conditions should remain VRF even in the rain or freezing rain, but occasional MVFR ceilings are possible.

Early Friday morning the winds will abruptly shift to the Southeast out of Turnagain Arm with gusts up to 40 kt. This will end the wind shear with the winds making their way to the surface. By late morning, winds will remain strong but shift to the south- southwest as a cold front moves through from the southwest. The biggest uncertainty is whether there will be a quick burst of snow (possibly down to IFR conditions) as the front moves through, or if the rain ends before the air gets cold enough to switch to snow. All conditions should improve Friday evening.