HELENA, Mont. — Flood, snow, avalanche and fire alerts popped up Monday from Idaho to Colorado, as parts of the U.S. interior that were paralyzed by blizzards and floods last month braced for round two of an unusual weather phenomenon.
Welcome to springtime in the Rockies and parts of the Great Plains.
It’s not unusual for floods, snow and fire to co-exist in the Rockies thanks to powerful storms blowing through the mountains, melting snow swelling waterways and high winds sweeping across dry grasslands and trees that haven’t seen their first green shoots and leaves.
Those conditions are what drove a wildfire Sunday on southeastern Montana’s Northern Cheyenne Indian Reservation, where a house fire sparked a blaze that quickly burned through 1,700 acres of dry grass and trees. It forced evacuations Sunday in Lame Deer, a town of about 2,000 people, before fire crews were able to contain it.
But what is unusual is what’s coming next. A storm system that is moving in from the Pacific Ocean is forecast to intensify and form into a new inland “bomb cyclone.”
A bomb cyclone is a rapid drop in air pressure and often is over or near oceans or seas because it requires warm moist air smacking into cold dry air, along with volatile weather from the jet stream. The central and mountain part of the country may get one of these every few winters, said Greg Carbin, forecast branch chief for the National Weather Service’s Weather Prediction Center in Maryland.
But this would be the second such storm in less than a month. The March 13 storm caused massive flooding in the Midwest, a blizzard in Colorado and Wyoming, and produced winds of between 96 mph and 110 mph.
This week’s bomb cyclone is expected to be similar in intensity and in snowfall, meteorologists said. Heavy, wet snow will fall from the Nebraska panhandle through south central and southeastern South Dakota into western Minnesota. Wind speeds can reach 50 mph to 60 mph across Kansas.
But first, the storm is expected to cause flooding in Idaho and western Montana, and dump up to 2 feet of snow in the mountains of Montana and Wyoming as it moves in from the Pacific Ocean. Parts of Colorado that were under a fire warning Monday are expected to see snow and temperatures drops of more than 40 degrees by Wednesday at the southern edge of the storm, meteorologists said.
