HAMILTON - Winter's unusually heavy snowpack is giving way, prompting the National Weather Service to issue a flood warning for the Bitterroot River and small streams throughout Ravalli County.
Late Tuesday, the Bitterroot was nearing flood stage at Darby, Bell Crossing and Florence - and was expected to continue rising, according to the National Weather Service.
In addition, forecasters said "snowmelt will combine with rainfall to cause area streams and creeks to spill over their banks. Creeks running through clogged culverts may flood properties nearby. Water may also spill over roadways and low bridges where the creeks flow near or under.
"Creeks flowing from the Bitterroot Mountains are especially prone to flooding."
The Weather Service warned that by Wednesday night, county roads along the Bitterroot River from Hamilton to Florence could see some flood waters.
Late Tuesday, the Bitterroot River was at 7.3 feet at Darby. Flood stage is 7.5 feet, and the water was expected to rise to 8.0 feet by Wednesday night - with additional rises to follow.
"At 8.0 feet, flooding to low-lying areas adjacent to the river will occur," the forecast said. "Flooding can also be expected to inundate several county roads that are prone to flooding."
The Bitterroot River last reached 8.1 feet at Darby on May 20, 2008.
At Bell Crossing near Victor, the river hit 10.8 feet late Tuesday. Flood stage is 11.0 feet - and was likely reached overnight.
Near Florence, the Bitterroot was at 12.23 feet, and near Missoula it was at 10.21 feet. Flood stage as the river reaches Missoula is 11 feet.
Forecasters said the river would exceed flood stage near Missoula by Wednesday morning, and could reach 11.6 feet by midnight.
"At 12.0 feet, flooding of farmland and some roads along the Bitterroot River from Lolo to the confluence with the Clark Fork River is possible," the forecasters said.
Wednesday's forecast for the Bitterroot Valley includes an 80 percent chance of rain, with high temperatures in the low 60s. Showers are likely to continue into the evening, under mostly cloudy skies.