A burst of Arctic air could combine with a strong Pacific storm today to give much of the Rocky Mountain West a winter storm shellacking over the weekend.
The National Weather Service in Pocatello issued a winter storm warning Thursday for the weekend, calling for snow accumulations of 16 to 30 inches of very wet snow over a three-day period.
"Persons planning travel through the higher elevations of Eastern Idaho this weekend should consider putting off such plans until a later time," the service said in the warning.
"The heavy stuff will start Friday afternoon and probably continue off and on through the weekend," said Greg Kaiser, a meteorologist with the National Weather Service in Pocatello. "A lot of Pacific moisture is getting pulled in from the Southwest, and it doesn't really look like there's going to be a break from it until Monday."
Kaiser said Southern California and other parts of the Southwest will be hit very hard once again, "but there's going to be plenty of moisture that's going to get over the Sierras and into Idaho as well."
The storm will be followed by extremely cold temperatures next week, Kaiser said. "It looks very, very cold through the brunt of next week, well below zero," he said. "But for this time of year, it's certainly not that unusual. It's actually pretty normal."
Earlier this week, meteorologists issued warnings that a once-in-a-generation storm could be brewing for much of the North American continent if moisture-laden storms from the north, west and south converge as computer models predict. A series of warm, wet storms are heading east from Hawaii; an Arctic mass of cold air is chugging south from Canada; and a warm, moist storm system is moving north from the Gulf of Mexico.
All three systems are likely to meet somewhere in the country's mid-section next week. In Idaho, however, only two of those systems are likely to collide.
"There's a big low pressure forming, kind of stationary just off the Washington coast," Kaiser said. "The flow is over the Southwest, which is what is going to pull it in off the Pacific and up into our area. And that should sit pretty still through the weekend."
The Sawtooth National Forest Avalanche Center issued a forecast Thursday morning predicting between 1 and 2 feet of snow in the mountains.
"This storm system has significant moisture associated with it, so expect heavy snow throughout the weekend," wrote forecaster Jake Amadon. "If we receive the anticipated snow and associated winds over the weekend, the avalanche danger will increase, and we will once again be working low-angle terrain while in the backcountry."
If the storm hits as anticipated, it could stress road crews. But Idaho Transportation Department Public Affairs Specialist Bryant Kuechle said clearing snowy roads is business as usual for the state's snowplow drivers.
"We certainly are aware of the weather conditions that are in the forecast," Kuechle said. "Our snowplow drivers and winter road crews are prepared to work as many hours, as many days as it takes to keep the highways clear and passable."
Kuechle said travelers should check the Idaho Road Report at (888) 432-7623 or www.itd.idaho.gov for updates about road conditions.
Additionally, the new snow, should it arrive, could help the state take a few steps away from a six-year drought that has plagued farmers, ranchers and the state's tourism industry.
In the mountains of the Snake River Basin, which supplies most of Idaho's irrigated farmland, the snowpack was just 80 percent of average this week. The Big Wood River basin's snowpack was 85 percent of average. The Payette River basin, which contains several large reservoirs and is popular among summer whitewater paddlers, was at 65 percent of average.
