First things first, twenty inches of snow was reported with this storm at Madison, Minnesota with more than nineteen inches in Bloomington, in the south Metro.
Shown below is a graphical representation from the National Weather Service of the estimated water content of Sunday and Sunday nights precipitation. Some of the moisture fell as a wintry mix in far southern Minnesota. Note the patches of yellow that depicts estimates of more than an inch and half of water. This matches up well with the 1.8 inches of water content reported from Springfield, Minnesota.
On Tuesday mornings, beginning in February, the National Weather Service cooperative observers take core samples to estimate the total Snow Water Equivalent in the entire snow depth. In weather lingo, we refer to it as a snow biscuit, because it looks like a biscuit (a thick one) when you first pull the sample out of the snow.
A metal cyclinder with cutting teeth is inserted through the snow until it reaches the hardened surface.
The cyclinder’s core sample is then melted down to get a real close estimate of the water contained in the snow.
Water equivalent of snow depth.
Photos courtesy of the Marquette National Weather. Pardon the fuzziness. It was probably bitter cold when they captured this image of taking a sample.
In addition, the National Office of Hydrology Remote Sensing Center (NOHRSC) takes gamma radiation measurements from low level airplane flight lines of the snow and ice water content. Their data, along with the cooperative obsever reports, is of paramount value in hydrologists projecting the potential river crest from the snow melt.
I guess, the silver lining in this event, most of the precipitation fell south the Red River basin.