05-10-2013, 08:39 AM
Possible flooding in SW Montana Rivers.
Western Montana rivers headed for high water, flood levels
1 hour ago • By DAVID ERICKSON and ROB CHANEY of the Missoulian
The unusually hot and sunny weather expected in western Montana this weekend and into next week has forecasters at the National Weather Service in Missoula warning of a dangerous spike in river levels.
According to NWS hydrologist Ray Nickless, high temperatures will melt the snowpack enough to increase average water levels on the Clark Fork and Bitterroot rivers by about one foot by Saturday.
The rivers could reach their forecasted peak flows by Tuesday.
“This is a dramatic increase in water in a very short period of time,” he said.
The Clark Fork River above Missoula has the potential to reach 6.8 feet by Tuesday, and the level below Missoula could reach 7.5 feet. The flood stage for the Clark Fork in that area is 10 feet, Nickless said. The Clark Fork rose to 14 feet in 2011 when it flooded several neighborhoods in Missoula.
The Bitterroot River near Missoula has the potential to reach 9.3 feet by Tuesday, and the flood stage there is 11 feet.
The Yaak River in northwest Montana is forecast to reach flood stage by Friday evening and possibly exceed it on Saturday. The Yaak reached 6.9 feet on Thursday, with flood stage at 8 feet. The flood watch is in effect through Sunday evening.
The National Weather Service also issued a warning for sharp rises in the Flathead River and nearby streams through early next week. The Middle and North forks of the Flathead were of particular interest, because their combined flows may push the main stem of the Flathead by Columbia Falls to its 13-foot flood stage by Monday.
“With these temperatures so far above normal, the snow is just melting off very fast,” Nickless explained. “The maximum temperature in Missoula was 82 degrees on Wednesday, and normally this time of year the maximum temperature is 65 degrees.”
The snowpack in the area is about average or slightly below average, Nickless said, but the warm weather is just melting it off at a faster pace than usual.
He also noted that while it is possible for rivers in the area to reach their peak flow by Tuesday, rainstorms later in the spring could cause water levels to surge even higher.
“This could be our peak for snowmelt, though,” he said.
Nickless said that anyone who plans on being near or on rivers for recreational purposes through the weekend should expect very high, very fast-moving water.
“You always get kayakers, but they’re prepared,” Nickless said. “If you are just an average person going out fishing, you should be extremely careful. If you fall in by accident, hypothermia can set in pretty quick with the ice-cold waters.”
Updates on river levels will be posted at weather.gov/missoula or information can be found by calling (406) 329-4840.
The rest of the summer won’t have a dominant trend this year, according to Jess Aber at the Montana Department of Natural Resources and Conservation drought advisory committee. That’s because Pacific Ocean temperatures are balanced between the levels that create dry/warm El Nino conditions or wet/cool La Nina patterns.
“It’s important to understand that a neutral (forecast) does not mean we could not see excessive heat or cold, wetness or dryness in the months ahead,” Aber said in an email. “This is because Montana has an inherently highly variable climate, especially east of the Continental Divide. Low streamflow and a wildfire season are to be expected for Montana in any given year.”
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