Recent warm weather is expected to continue into mid-May and cause Northwest Montana rivers and streams to rise over the next couple of weeks.

“This warmth that will go into mid-May or even further ... it’s just causing a lot of rivers and streams to rise very rapidly,” said Dan Zumpfe, a meteorologist with the National Weather Service in Missoula. “We’re watching these rivers very closely to show signs that they exceed action stage.”

Zumpfe explained that “action stage” is when people living in flood-prone areas should start to make preparations and pay attention to river levels on a daily basis.

Temperatures across much of Western Montana have been in the mid- to upper 70s for the last few days, or about 10 to 15 degrees above normal for this time of year.

That’s a complete turnaround from April’s much cooler-than-average weather, which put a damper on snowmelt.

“What’s more startling is our nighttime temperatures,” Zumpfe said of temperatures not dropping below 40 degrees in the mountains overnight. “That may be an even bigger concern for the rapid snowmelt, rather than the daytime temperatures. There is no end to the snowmelt. It’s almost continuous.”

That will feed rivers and streams for the next few weeks. National Weather Service hydrographs show the Yaak River at Troy just a foot below action stage. The river, which runs high or floods just about every year, is expected to reach action stage by this weekend.

The North Fork Flathead River at the Canadian border also is expected to reach action stage by this weekend, and the main stem Flathead River at Columbia Falls is expected to reach action stage by early next week.

The National Weather Service is advising the public to be cautious around bank-full rivers and streams that present drowning dangers and hypothermia risks.

On the Web:

For updated area river levels, go to www.wrh.noaa.gov/mso/hydrology/composites.php.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.