As the first signs of spring flooding emerge this week across southern Minnesota, weather conditions have been nearly ideal for a relatively slow, if not completely harmless, snowmelt.
With daytime temperatures gradually warming and nighttime temperatures dropping just below freezing, the snowpack has trickled away, keeping streams and rivers from a rapid rise.
What's more, the forecast for the next week calls for more of the same.
"So far this has been a perfect snowmelt," Dan Luna, chief meteorologist for the National Weather Service Twin Cities office, said Wednesday.
Luna compared the early spring melt to 2013, when the region avoided major flooding despite similar conditions.
"A really bad snowmelt," he said, "is what happened in Nebraska," where early warm weather and heavy rains this month overcame flood protections and led to devastating damage.
Luna noted that it hasn't rained in central or southern Minnesota for a week, and no significant precipitation is expected in the next week. As a result, he said, the region has begun shedding water and will lose even more in the next five to six days.
A week ago, 13 inches of snow was measured at the Minneapolis-St. Paul International Airport. Now, there's just a trace.
Even so, Luna added, much of Minnesota isn't yet out of the woods. "We will have widespread moderate flooding throughout the state when all is said and done," he said.
In that scenario, high water could force the closing of roads and bridges. Many of the cities and towns in the Minnesota and Mississippi river valleys, however, are mostly protected by dikes, levees, spillways and other flood controls that should hold back all but record flooding.
In Mankato, the Minnesota River is expected to crest at about 25 feet — 3 feet over flood stage — early next week.
"That's no small amount of water," City Manager Patrick Hentges said. But pumps and a levee protect the city if the river rises well over 30 feet.
"The city is pretty heavily protected," he added, noting the pumps have been turned on and city crews are checking the levee.
While there has been no flooding in the city limits, a few rural roads are threatened as tributaries spill over, Hentges said. "It's an inconvenience," he said. "We live on a river system … and it's just part of what we deal with."
In Garden City, an ice jam on the Watonwan River sent water rushing into a neighborhood Tuesday, prompting several residents to flee. But by Wednesday, the ice had passed, the Mankato Free Press reported.
In Chaska, the Hwy. 41 bridge at the Minnesota River will close at 9 a.m. Friday in anticipation of flooding. The Hwy. 101 bridge between Chanhassen and Shakopee would be an alternate route.
In Henderson, road closures have become a spring rite when the snow melts and sometimes during heavy rains. "It's a pain in the butt as far as getting around," said City Administrator Lon Berberich. "Hwy. 19 east is closed, Hwy. 93 north is closed and County Road 6 to the north is closed. A 15-minute trip now takes 40 minutes."
The towns and cities along southern Minnesota streams and rivers aren't the only places benefiting from the mild weather.
A recorded forecast for the Red River Valley on Wednesday described the weather in northwestern Minnesota and eastern North Dakota as "quiet," with "good melting conditions" and no rain or snow through Saturday. Highs were expected in the mid 30s and lows in the 20s.
"Happy vernal equinox," the recording said, announcing the first day of astronomical spring, when the length of daytime and nighttime are the same.
Nick Carletta, a National Weather Service meteorologist in the Grand Forks office, said the Red River basin floods nearly every year.
While the region's snowmelt has been gradual so far, much of the water sits on frozen ground and has yet to drain into streams and rivers.
Carletta said there is a chance of light rain or snow on Sunday, but he doesn't expect the precipitation to have much effect on flooding.
The forecast for the Red River Valley next week is less certain. Continued warming is possible, which Carletta said would be favorable if the area avoids a heavy rainfall of several inches or more.
But cold weather could spell trouble. The longer the region goes into spring with snow and ice on the ground, the more likely the temperatures will rise quickly and the melt will be rapid, Carletta said.
Staff writer Mary Lynn Smith contributed to this report. Dan Browning • 612-673-4493
