If all the snow still sitting in the headwaters of the Sun River drainage melted at once, it would equal 2 to 4 feet of water.
"There is just tons and tons of water up in the mountains," said Ben Schott, a meteorologist with the National Weather Service in Great Falls.
The first round of flooding in northcentral Montana occurring now is mainly the result of near-record rainfall across the region, not snowmelt, Schott said.
Round 2 could occur once large amounts of snow begin to melt, he said. To date, very little of the snowpack has melted, he added.
"The bigger picture is this threat will linger most likely into July," Schott said.
So far, cool temperatures in the mountains have slowed the melt, with minor runoff from snow at elevations below 8,000 feet.
"Above 8,000 feet, some of those places have actually increased the water in the snow because they've had additional snowfall," Schott said.
Temperatures in the upper 60s are forecast for this weekend and 70s are predicted by early next early week.
Between a half-inch and 1 inch of rain fell in the Sun River corridor Thursday as of late afternoon, as widespread rain continued to impact northcentral Montana. The system was expected to run its course Thursday night, with a chance for scattered rain showers today.
The Sun River at Vaughn, just west of Great Falls, was rising faster than the forecast Thursday.
Joseph Beard of the Vaughn Flood Control District said water from the Sun had reached the very bottom of the levy, where it begins to slope upward.
"Right now we're feeling pretty good," Beard said.
The river was at 7.8 feet, instead of the forecasted 7.3 feet. Flood stage is 6 feet. The river is forecast to peak today at 8.5 feet, Schott said.
River levels are very low compared to the flood of 1964, Beard said.
As of Thursday, outflows at Gibson Reservoir, which affects flows in the Sun River downstream, were 10,500 cubic feet per second. The river begins flooding at 10,000 to 11,000 cfs. Before the reservoir began releasing water into its spillway Sunday, outflows were 2,800 cfs.
Inflows to the reservoir also were at 10,500 cfs Thursday, Schott said. |