More than 6.5 inches of rain fell in 3.5 hours this morning in the Mora, MN area. Early reports indicate the same storm also dropped significant amounts of rain on the Wisconsin side.
Local rivers are responding to the rain as expected, with water levels spiking upwards. The Snake River, a major St. Croix River tributary, has already risen five feet this morning.
It shows no signs of slowing down, and that wall of water will be working its way downstream over the next several days.
The National Weather Service predicts the river at Stillwater will rise a couple feet by this weekend. The river was already above no-wake levels, and this precipitation may keep it there longer.
The National Weather Service says the intensity of the rain may be “historic.” The Duluth office of the agency tweeted that the rainfall intensity was “INCREDIBLE!”
One amateur meteorologist analyzed the data and said it looked like a “1,000-year” event.
The original chart (just the curves) is from another nearby project in east-central MN, but it's close enough, IMHO. It looks to me like the 6.47 inches in approx. 3.5 hours (4:30a to 8:00a) at Mora is likely a greater than 1,000-year rainfall event. pic.twitter.com/KaIs7R4SA1
— Charlie Tango Bravo (@mnsotn) July 12, 2018
Additional rain is possible later today, raising alarms about flash flooding.
“As one area of thunderstorms moves out of Minnesota and into Wisconsin, additional showers and thunderstorms were developing along and ahead of surface low pressure moving out of South Dakota,” the National Weather Service reported. “While heavy rainfall rates are possible from these cells, the chances for flash flooding will be best in areas of eastern Minnesota which were soaked overnight.”
Rainfall map from the past 12 hours, showing 4 to 7" has fallen from the Lake Mille Lacs area southeast to Mora. Significant flooding has been reported in the Mora area. We would really appreciate any additional rainfall or flooding reports. #mnwx pic.twitter.com/m1JkMMH00m
— NWS Twin Cities (@NWSTwinCities) July 12, 2018
Be careful out there, and stay tuned to St. Croix 360 for updates!