Warm temperatures and an “atmospheric river” of precipitation that flowed into northwestern Montana this week have generated a state of emergency in Montana’s northwesternmost county, Lincoln, as local waterways run unseasonably high.

Around 12 p.m. Wednesday, the National Weather Service started issuing flooding watches as area snowpack sites reported 24-hour precipitation totals that were approaching record levels. NWS meteorologist Dan Borsum told Montana Free Press Thursday that the “rain-on-snow” nature of the recent precipitation has led to widespread flooding. 

Borsum called the weather pattern “unusual” for mid-December, instead likening it to a warm April.

Zach Sherbo, the public health manager for the Lincoln County Health Department, said in a Thursday afternoon phone call that additional precipitation is expected through Thursday evening, so rivers could continue rising into Friday.

The Lincoln County communities of Libby and Troy have been hit the hardest by the deluge, which prompted emergency services personnel to issue a state of emergency Thursday afternoon. Residents are cautioned against unnecessary travel and those served by the Libby city water supply are under a boil-water order as a precaution in the event of water supply contamination. School has also been canceled for students in Libby and Troy, Sherbo said. 

The Lincoln County Sheriff’s Department has identified a handful of bridges that have been compromised or are washed out as a result of flooding. It suggests residents looking for information on road closures and bridge conditions review an interactive map that is available online and linked in a press release posted to the Lincoln County Health Department’s Facebook page. 

“It’s going to take a long time to recoup from this, just structurally, just with the bridges we’ve lost already and the condition that they’re in and going toward,” Sherbo said. “It’s a pretty big combined local effort right now.”

Justun Juelfs, the Kalispell-area maintenance chief with the Montana Department of Transportation said three stretches of state-managed roadways were closed or under monitoring status as of 4 p.m. Thursday. 

An approximately 80-foot section of the Farm to Market Road south of Libby has washed out as Libby Creek carved a new channel. MDT is also monitoring erosion that is occurring along a U.S. Highway 2 bridge southeast of Libby and along a section of Highway 56 near Bull Lake. Juelfs encouraged motorists to review MDT’s road conditions report for up-to-date information on impacts to state highways.

The Army Corps of Engineers is assisting with sandbag-filling and distributing efforts and the Red Cross has set up a shelter for those in need at the Assembly of God Church in Libby, according to Sherbo.

The Montana Disaster and Emergency Services agency is also lending a hand with the flood response. In an email to MTFP, Anette Ordahl with DES wrote that a district field officer and a recovery coordinator are on the ground in Libby to offer assistance.

In a Thursday afternoon press release, Gov. Greg Gianforte noted that Sanders and Flathead counties have also recognized the flooding by issuing emergency or disaster declarations. Up to four inches of additional rainfall are expected across western and south-central Montana, according to a disaster declaration Gianforte’s office included in a 3 p.m. press release.

The National Weather Service reported Thursday morning that the Bear Mountain snowpack monitoring site, located just across the border in Idaho, received 6.5 inches of precipitation as of this morning, making it the third-wettest 24-hour period for the site in its 44-year monitoring history. The six-day precipitation total for Dec. 6-11 is 13 inches.

Borsum, with the National Weather Service, said the recent, unseasonable warm spell in western Montana combined with the “super strong” atmospheric river to melt early season snowpack and drive flooding. A similar rain-on-snow event in early June of 2022 led to widespread flooding in parts of south-central Montana that required extensive repairs to roadways and bridges. 

Thursday, the Yaak River near Troy surpassed its official flood stage, running at more than 7,500 cubic feet per second. Its usual volume for this time of the year is about 200 cfs.

The Fisher River near Libby was also nearing flood stage. As of Thursday afternoon, it was running at nearly 4,000 cfs, more than 20 times its usual volume for mid-December.

Zeke Lloyd and Jacob Olness contributed to this reporting.