A wave of warm, wet and windy weather passing through Southcentral Alaska over the next two days will increase road and avalanche hazards throughout the region, meteorologists said Wednesday.
Michael Kutz, with the National Weather Service office in Anchorage, said a storm front moving across the northern Gulf of Alaska was expected to bring half an inch of rain, along with snow and gusting winds, to much of Southcentral by the weekend.
Kutz advised people who can avoid driving during the warmup to do so. For those who are on the roads, he suggested leaving more travel time and more space between vehicles.
"Don't go out, because things are going to be a little nasty out there," he said. "Unfortunately, a lot of us still have to come to work."
The weather service issued a special weather statement on the warmup, as well as a high wind watch in effect overnight Wednesday into Thursday morning for areas along Turnagain Arm. The eastern Alaska Range will be under a wind advisory through noon Thursday.
"The major band of stronger winds is going to stay just south of the Anchorage area," Kutz said. "We're looking for a mix of precipitation starting tonight into tomorrow, probably midday (or) just a little longer — it depends on how long that system takes to move through the area."
In Southcentral, wind speeds are expected to hit 40 to 55 mph with gusts from 65 to 75 mph; Alaska Range winds should be 20 to 35 mph with gusts to 60 mph.
Southcentral temperatures are expected to "dramatically warm up" overnight Thursday into Friday as the low-pressure system approaches.
"Eventually the low will move inland, and this will allow for warm Chinook winds to spread into interior locations of Southcentral," the weather service said. "This represents a major change in the weather pattern from cold and snowy to rather warm, with temperatures pushing above freezing across many locales."
Although Anchorage will likely be on the lower end of the projected wind speeds, Kutz said, drivers can expect slick conditions as rain and snow fall on roads that remain below freezing temperatures.
"The places where it gets down to bare pavement, that's where the biggest chance of slippery conditions will be," Kutz said. "There's also going to be areas of standing water as well, because the ground is frozen and can't absorb it — those areas will be treacherous as well."
Avalanches in Southcentral's backcountry will be "a very large concern" over the coming days, Kutz said, because the precipitation is likely to form a separate layer on top of existing snowfall.
"It's going to be places like Hatcher Pass, Turnagain Pass and Thompson Pass by Valdez," Kutz said. "The initial snow that falls with this thing is going to be kind of heavy and wet."
On Wednesday morning, the Chugach National Forest Avalanche Information Center was listing moderate avalanche danger for all elevations of Turnagain Pass. The Hatcher Pass Avalanche Center reported considerable avalanche danger there above 3,500 feet last weekend, falling to moderate at lower elevations.
Wendy Wagner, an avalanche forecaster at the Chugach center, said she and other backcountry enthusiasts were closely monitoring the storm system, which is likely to improve recreational conditions in its wake.
"It's kind of exciting — it's our first big, warm, wet storm for the year," Wagner said. "Things are going to get kind of spicy starting tomorrow."
Due to the avalanche danger, Wagner's immediate recommendation was that people avoid backcountry areas this weekend.
"We'll typically get a cycle where we get large, wide avalanches that go down to sea level," Wagner said. "When it gets this big, we like to keep it simple and we tell people, 'Stay out of avalanche terrain.' "
Wagner recommended that after the system passes, people heed what forecasters call a "48-hour rule" before recreating on affected slopes.
"It's best to let the mountains sit for 24 to 48 hours after a storm, and that gives the snowpack time to adjust," Wagner said. "Most avalanche accidents occur the first day after a storm clears up."
Wagner said the slides are likely to bury alder trees and bolster a snowpack that's been only half as deep as usual. Both effects are a boon to snowmachiners, who have been taking advantage of January's uptick in snowfall.
"On the Chugach National Forest, every motorized zone is open this year, and that's the first time we've had every zone open in three years," Wagner said. "There's a lot of places to recreate — after this current cycle."
Although Kutz said some Southcentral temperatures are likely to top 40 degrees on Thursday, the warmth won't persist.
"Our temperatures will start sagging back down again below freezing going into the weekend," Kutz said. "Whatever snow and ice is left will be real crunchy, real hard, extending the possibility for slipperiness."
By Friday, meteorologists expect high temperatures in Anchorage to be in the 20-degree range, with overnight lows in the single digits. Highs should fall to the low teens Saturday and possibly single digits by Monday.
"We've got an interesting about 36 hours' worth of weather coming up here," Kutz said. "It's gonna be a nasty kind of mix; there's no two ways about it."