A mixed bag of weather is expected to push rivers across Western Montana, including the Flathead River, to flood stage this week.

The National Weather Service in Missoula is forecasting light rain, about a quarter inch, hitting Northwest Montana Monday night and today, followed by a dry Wednesday with temperatures in the 70s.

Then the region is expected to get about an inch of rain on Thursday. The chance of heavy rain on Thursday is listed at 100 percent by the Weather Service.

All Flathead Valley rivers are expected to see higher flows through the week.

The Flathead River at Columbia Falls is expected to reach its 14-foot flood stage by Wednesday and continue rising, possibly up to 15 feet by the weekend. The Middle Fork Flathead River at West Glacier is expected to reach flood stage by Friday.

“It looks like it’s going to start taking off now,” said hydrologist Ray Nickless, referring to the Flathead River system.

Nickless stressed that river forecasts can change rapidly depending on how rivers and streams react to rain and the ongoing snowmelt.

Scott Sampey, director of the Flathead County Office of Emergency Services, said if the predicted rain hits this week, some area creeks likely will spill over their banks. Most creeks in the county retreated a bit in the last couple of days, he said, as did the Stillwater River.

County officials plan to “keep a close eye” on the Stillwater, the Middle Fork and the North Fork of the Flathead River all week, Sampey said.

“Those are probably all in the action stage, which means they could go over their banks,” he said. “Depending on where you live, you could have flooding.”

The Swan River downstream from Swan Lake is expected to rise gradually, possibly reaching flood stage by the end of the week.

While flows dropped somewhat on the Stillwater River over the weekend, they are expected to rise above flood stage again through this week.

“The Whitefish River could get near flood stage by this weekend,” Sampey said.

In Lincoln County, the Yaak River is expected to return to flood stage this week, and the Fisher River is expected to hit flood stage by the weekend.

Due to flooding concerns, it does not appear that Flathead Lake will reach its full pool elevation by the usual June 15 target date.

The U.S. Army Corps of Engineers has ordered Kerr Dam, which controls flows out of Flathead Lake, to manage the lake for flood control.

“Because of the above average snowpack and the potential for localized precipitation, the Corps has instructed PPL that the lake elevation needs to be at a level less than full pool by June 15,” according to a press release from PPL Montana, which operates Kerr Dam at the foot of the lake.

“The timing of when Flathead Lake will achieve its full pool elevation of 2,893 feet is unknown at this time.”

The lake level most recently was at an elevation of 2,888 feet. Kerr Dam on Monday was releasing about 34,000 cubic feet of water per second, with the flow expected to rise steadily all week. The lake is expected to reach 2,891 feet by the end of this month.

Snowpack in the Flathead River Basin is 186 percent of average.

So far, Flathead County has distributed about 10,000 bags for sand, Sampey said. The county will get more bags from the Army Corps of Engineers this week.

Sand and bags remain available at the Evergreen Fire Hall. Depending on what happens in the next couple of days, Sampey’s office is preparing to have more bags and sand hauled to other fire stations around the county.

“We’re waiting for some more predictions to be sure we get equipment to the right spots,” Sampey said.

On Friday, officials from the Federal Emergency Management Agency and the state emergency services office are scheduled to meet with employees in the Flathead County Planning Office to explain the various paperwork required in the event of flood recovery efforts.

And, Sampey said, the Flathead City-County Health Department has issued warnings to some property owners about emptying septic tanks in advance of potential flooding to help avoid water contamination.

“We are still taking this very seriously,” Sampey said.

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