Alaska winter storm brings blizzard, snow and ice to Anchorage region

A Gulf of Alaska storm is bearing down on Southcentral Alaska with snow, freezing rain and high winds timed to disrupt the Monday evening and Tuesday morning commutes, the National Weather Service said.

Forecasters in Anchorage posted a Blizzard Warning for Thompson Pass and Winter Weather Advisories across the Anchorage Bowl, the Matanuska Valley and the Kenai Peninsula, according to the NWS Anchorage forecast discussion issued at 5:06 a.m. AKST Monday. A strong low is tracking toward the southern Kenai Peninsula and Kodiak Island, tightening the pressure gradient over the Gulf and driving gusty winds inland through Tuesday.

The storm matters because it is aimed at Alaska’s population center, not its empty quarter. Anchorage is the state’s largest city, home to about 290,000 people, and the advisories cover the commutes that move them. The precipitation is forecast to start as snow, then flip to freezing rain and rain as warmer air pushes north early Tuesday, a transition that is hard to forecast and hard to drive through. November is early for a snow-and-ice storm in the city.

Thompson Pass, on the Richardson Highway north of Valdez, took the sharpest warning. The NWS called for eight to 16 inches of snow, winds gusting to 45 mph and visibility falling to a quarter mile in blowing snow, with blizzard conditions from 11 a.m. Monday to noon Tuesday, the Blizzard Warning said. Farther south, the NWS Juneau office kept a Winter Storm Warning for Haines Borough and Klukwan until 6 p.m. Monday, with eight to 12 inches expected and two to three inches already on the ground at the Haines Border Crossing by 7 a.m., the warning said.

The Anchorage Hillside and Eagle River sit under an advisory for two to eight inches of snow, a light glaze of ice and winds gusting to 60 mph along the southern hillside, the NWS advisory said. The lower Matanuska Valley, including Palmer, Wasilla and Big Lake, could see up to two inches of snow and a few hundredths of an inch of ice. The Kenai Peninsula, from Kenai and Soldotna out to Homer, is forecast for one to eight inches of snow and up to a tenth of an inch of ice, with 45 mph gusts along the coast.

The common thread is the commute. Each advisory names the Monday evening and Tuesday morning drives as the window when roads, and especially bridges and overpasses, turn slick. Freezing rain on packed snow is the combination that closes roads and delays schools.

The forecast turns on timing. Precipitation will begin as snow across Southcentral, the NWS said, then transition to freezing rain and rain as warmer air moves north early Tuesday. The greatest chance of accumulating ice falls Tuesday morning. Colder air draining south from the Matanuska Valley through the Glenn Highway corridor into Anchorage could hold the snow and freezing rain in place longer. The forecasters flagged the uncertainty: if the cold air erodes slowly, snow and ice totals climb; if warm air arrives quickly, the city flips to rain.

Winds are the other half of the storm. Northerly gusts to 55 mph are expected around Seward this afternoon and tonight, the NWS said, with east to southeast winds of 55 to 65 mph over eastern Turnagain Arm, the Interior Kenai Peninsula and Whittier late Monday into Tuesday morning. The Anchorage Hillside advisory warns that gusts could damage trees and power lines. At Ted Stevens Anchorage International Airport, forecasters expect gusts near 20 knots and possible low-level wind shear, with a 20% to 30% chance of light snow reaching the terminal Monday evening.

The same active Pacific storm track is bringing rain and high-elevation snow to the Pacific Northwest, the Weather Prediction Center said in its short-range discussion, with the heaviest precipitation late Monday into Monday night. South of that, an upper-level low drawing Gulf moisture is producing heavy rain and a flash-flood threat over southern Texas. The Lower 48 is mostly mild and wet this week, not snowy. The winter storm driving Monday’s search interest is an Alaska story.

The NWS advises travelers to keep a winter survival kit in the vehicle and, if stranded, to stay with the car, the agency’s winter safety guidance says. The Alaska advisories point drivers to 511.alaska.gov for road conditions. The Blizzard Warning is the bluntest of the bunch: whiteout conditions will make travel very hazardous.

What I think

The snow totals are not the story. Eight to 16 inches at Thompson Pass is a workday for that stretch of the Richardson Highway. What makes this one worth watching is the freezing rain.

Freezing rain is the winter hazard that forecasters respect most, because it coats roads, power lines and aircraft surfaces in clear ice that is hard to see and nearly impossible to drive on. The NWS flagged Tuesday morning as the window when warm air overruns the cold surface layer trapped in the Matanuska Valley and the Anchorage Bowl. If the cold air holds longer than modeled, the city gets more ice; if it erodes quickly, the city gets rain and the problem moves to flooding. Either way, the Tuesday morning commute is the one to plan around.

Anchorage has been here before. Freezing rain storms have glazed the city’s roads for days at a stretch, and the NWS writes its advisories in plain language for a reason. November storms in Southcentral are not rare, but a storm that brings this much wind and this much precipitation-type uncertainty to the Anchorage Bowl before the ground is frozen and before drivers have put on winter tires is the kind that catches people out.

If you live in Anchorage or the Matanuska Valley, plan around the Tuesday morning forecast. If you are driving the Richardson Highway over Thompson Pass, the Blizzard Warning is not a suggestion. And if you are watching from the Lower 48, where the weather is mostly mild this week, the Alaska storm is a reminder that winter starts early the farther north you go.