MANKATO — National Weather Service flood forecasters have gamma radiation snow surveys provided by airplanes, snow cover images provided by satellites, and hydrologic modeling provided by supercomputers.
Even so, they still want the measurements of actual snow depth and water content provided by two guys named Bill and Paul, who've been driving a pickup over thousands of miles in Minnesota and Wisconsin the past week, tromping through the wet snow and sticking a metal tube through the soggy white stuff.
From Grand Marais to Fargo and from Gaylord to Rochester, Bill Odell and Paul Johnson have pushed the tube into the snow hundreds of times, dumped the captured snow in a baggie, measured its weight and done the calculation.
"It's really an opportunity for us to get out and get on the ground and verify," said Odell, a hydrologic technician for the U.S. Army Corps of Engineers.
During a recent stop in Mankato, Odell and Johnson, a survey technician, found a spot of undisturbed snow off of Bassett Drive not far from the Walmart parking lot. Four times they stuck the 1.5-inch diameter tube through the snow and the layer of ice below it. Sixteen inches, 16 again, then 13 and finally 9. The core of snow from each sample was dumped into the plastic bag, weighed and averaged.
The bottom line: 2.25 inches of water were on the ground in the form of snow.
Mankatoans saw the evidence of that accumulated moisture when temperatures rose into the 50s on Monday, creating ponds at intersections and streams running down hillside streets. But while the winter was a long and cold one, and snow depths rose substantially in January and February, the threat of flooding is below average this spring.
The amount of snow isn't extreme and it's not particularly wet.