Officials warn weekend warmup could cause significant flooding

The Idaho Office of Emergency Management says it is on high alert due to the possibility of flooding when temperatures climb above freezing this weekend.

In the last five weeks, Eastern Idaho has seen more snowfall than is normally seen all season long. First Alert chief meteorologist Michael Coats says more is expected Saturday evening. When combined with the rising temperatures expected Sunday, the National Weather Service in Pocatello says it is a recipe for flooding.

“We’re pretty confident there is going to be some flooding issues over some pretty wide spread areas,” Jeff Hedger with the NWS said.

Lemhi County is currently experiencing minor to moderate flooding in low areas near the Salmon River north of the city of Salmon, according to an IOEM press release.

The flooding we see in Eastern Idaho Sunday into Monday will not be caused by rivers flowing out of their banks in many areas, according to the NWS. Hedges says with our rising Sunday temperatures, the snow will turn to rain Sunday evening; however, before that the Snake River Plain will receive freezing rain, causing the snow pack to freeze. Once the rain starts to fall, it will have nowhere to go and runoff will flow into the streets, parking lots and low-lying areas.

“What is making this unusual is we have a pretty heavy snow back in the low elevations and the fact that this next wave has a lot of moisture packed into it so we are looking at high rainfall amounts,” Hedges said.

Currently, the Lemhi River, the Big Wood Rive and the Snake River near Weiser are all experiencing ice jam-related minor flooding.

Coats says past Sunday, the concern turns from sheet flooding to ice jam floods. Ice jams happen when shallower areas of rivers freeze faster than deeper areas, and the ice gets stuck where the river bends or curves.

“We are seeing a lot of concerns here from city and county managers, all across Idaho and Wyoming with this warm weather coming,” Coats said. “Especially for folks that live near river and flooding potential is going to be pretty high.”

Coats and the NWS warn everyone, no matter how close you live to the river, to be on alert for rising waters.

“They should be looking at getting some sandbags or looking at getting at where that water can go because if water can not drain off on your property, it has got to go somewhere,” Coats said. “Even if you don’t live near a river, and you live near a storm drain, try and keep things clear. Try and clear out drainage. Try and make sure low-lying areas are kept clear of as much snow as possible.”

The NWS will hold a conference call with emergency managers and meteorologists Saturday morning to discuss the risk of flooding.

You can find out more about flooding danger on the National Flood Insurance Program website or by calling 888-379-9531.