Way-above-average snow packs have started melting into rivers, bringing flooding problems to the Missoula, Bitterroots and Blackfeet-Seeley-Swan areas. More than 800 Missoula residents were put on notice last Sunday to possibly evacuate in low-lying areas according to the Associate Press.

“Even with that last warm-up, we haven’t really started the runoff yet,” National Weather Service meteorologist Genki Kino in a recent interview. “Last week’s warm-up and flooding was associated mainly with low-elevation melting from 5,500 feet elevation and below.”

The higher mountainsides still hold around 160 percent of the average snowpack for this time of year. In many places that’s more than 50 inches of snow-water equivalent, which is like 50 inches of rainfall waiting to be released.

The Clark Fork in the Missoula area should reach 13 feet this week. Causing increased flooding for Orchard Homes neighborhood which has already seen flooding over the past few weeks. The Bitterroot River is expected to reach 11.44 feet and cause minor flooding by this week. Officials are reporting this could be the worst flooding in more than 40 years.

With the Clark Fork, it is expected to approach major flood stage by Tuesday and to crest Friday. It would be the river’s highest level since 1975, said Ken Parks, deputy coordinator for Missoula County Disaster and Emergency Services.

This is coupled with a severe storm which hit the region on Sunday evening bringing strong winds, pea-sized hail, lightening, and rain. The storm blew down trees, signs and caused minor damage to some homes.

“If you live anywhere near a stream or waterway in western Montana you need to be prepared to leave your home,” he said. “This is going to come earlier than we expected. We’re trying to get out ahead of this thing and get the message out that this could be a very dangerous situation.”

West of Missoula, erosion along the Clark Fork brought high water dangerously close to holding ponds for the wastewater treatment plants in the town of Plains. The U.S. Army Corps of Engineers was asked to help the town secure the ponds.

Temperatures this week are expected to reach the 70s, which could accelerate melting of a mountain snowpack that hit record depths in parts of the state this winter. Currently there are no flood warnings for Mineral County.

Those traveling on forest roads should check Alerts and Notices on the Lolo National Forest website for current road closure information. Contact local ranger district offices also for current conditions.