Update 9:30 a.m. Tuesday:
Drivers on the Seward Highway between the Bird and Portage areas, from Mile 100 to Mile 80, could see delays of up to an hour for "avalanche hazard reduction work" between 8:30 a.m. and 2 p.m. Tuesday, according to the state Department of Transportation and Public Facilities.
Shannon McCarthy, a spokeswoman for the department, said crews would be using howitzer fire.
"They have some targets that they want to hit to see if they can bring down some of the smaller stuff, so they can prevent a larger avalanche later on," McCarthy said.
McCarthy said "difficult driving conditions" were being reported throughout Southcentral Alaska on Tuesday morning, but the delayed onset of the rain gave road crews a chance to prepare Monday.
"We knew this rain was coming, so we were able to treat the major highways yesterday with salt brine," McCarthy said. "They geared up for it and are hitting it 24/7 right now."
Update 7 a.m. Tuesday:
Four northern schools in the Mat-Su Borough School District were closed for the day Tuesday as freezing rain made some Mat-Su and Anchorage roads especially slippery.
"Due to icy road conditions, buses cannot transport in the Northern Valley, so Trapper Creek, Talkeetna, Su Valley, and Willow are closed," district officials wrote on MSBSD's website early Tuesday. "All other Mat-Su schools are open today."
Anchorage School District facilities were to open on a normal schedule Tuesday.
The National Weather Service issued an advisory calling for "light freezing rain" through 10 a.m. Tuesday in East Anchorage, the lower Anchorage Hillside and the Eagle River Valley.
Joe Wegman, a meteorologist at the National Weather Service office in Anchorage, said the freezing rain would be limited to parts of the city seeing both cold air and rainfall.
"Most of the precipitation is at higher elevations, but the cold air is at lower elevations," Wegman said. "It's that small area where the two overlap."
Wegman said Tuesday's conditions were different from the Jan. 26 heat wave and freezing rain that left roads across Anchorage icy, snarled traffic and prompted parents to question ASD's decision to remain open that day.
"Last time, the warm air came in with the precipitation right away," Wegman said. "This time we've had nearly a day where the temperatures have already been above freezing – all the pockets of really cold air have been scoured out."
After the freezing rain passes, conditions should give way to temperatures in the 40s and sunny skies.
"It'll be a very nice afternoon," Wegman said.
Original story:
An arriving warm front and heavy snowfall overnight Sunday in some backcountry areas was forecast to cause extensive dangerous avalanche conditions, as well as slick roads for the Tuesday morning Anchorage and Mat-Su commutes, forecasters say.
The above-freezing temperatures were entering the region from the Gulf of Alaska and heading inland, affecting the Seward Highway south of the city first and reaching Anchorage's higher elevations by Monday evening, said Anchorage-based National Weather Service meteorologist Eddie Zingone.
"We'll probably see temperatures creeping up slowing through (Monday) night," Zingone said. "The time of the warmest temperatures will probably start late Tuesday morning, when the winds shift to the southeast."
When that happens, the temperatures will jump to the lower-40s range, he said.
Anchorage meteorologist Rebecca Duell said a colleague who commutes to Anchorage along the Seward Highway from Girdwood offered a glimpse Monday morning of things to come – including snow shifting to rain – for the Anchorage area.
"He said it was slushy from Girdwood to Indian, and the slush over ice from Indian to the weigh station was making for some of the worst conditions he's ever seen," Duell said.
Temperatures increased in the Mat-Su communities of Wasilla and Palmer by Monday evening, although the predicted mixture of rain and snow hadn't reached them. But precipitation remained possible, Zingone said.
That mixture could also hit Anchorage, though it may be less severe by the time it reaches the city.
"We're still expecting (Tuesday) morning's commute to be one where people want to take it slow, leave early, because it will be more challenging than normal," Zingone said.
A Monday advisory from the Chugach National Forest Avalanche Information Center reported high avalanche danger at all elevations of the Turnagain area, including the Portage, Placer and Girdwood valleys.
"This is not a complicated situation," forecasters wrote. "Avoidance of avalanche terrain is the only way to 'manage' this problem today."
The recommendation against travel into avalanche terrain was echoed by the Anchorage Avalanche Center covering Chugach State Park, which reported on its website Monday that "natural avalanches are likely, and human triggered avalanches are very likely."
Aleph Johnston-Bloom, a forecaster at the Chugach National Forest Avalanche Information Center, said that the backcountry conditions leading to Monday's advisory began to develop Sunday afternoon.
"Whenever you get new snow, rising temperatures, high winds, those are the three red flags for increased avalanche hazard – and we had all three of those overnight," Johnston-Bloom said. "We received more than a foot of new snow, a rapid warm-up, and we had winds to 90 mph."
The high wind gusts were reported by weather sensors in Turnagain Pass, Johnston-Bloom said, and the deeper snowfall occurred in the Portage and Alyeska areas.
Southcentral remains in an "unsettled" weather pattern, according to Johnston-Bloom, and hazard levels for Turnagain Pass will remain high through at least Tuesday due to additional snow and winds expected overnight Monday. She advised backcountry enthusiasts to monitor avalanche advisories for areas they plan to visit this week and remain updated on weather conditions there.