FARGO — A torrential rain, such as the five-inch deluge that left the Grand Forks flooded the night of Sept. 20, often begs the question, “How much would this be had it fallen as snow?”
This concept has several problems. First of all, those were convective thunderstorms with strong updrafts in unstable air; those conditions are very unlikely in air cold enough to snow.
Secondly, rain falls hard and fast, but snowflakes catch the air and waft down slowly. Those storms would have moved on before they would have had enough time to have dropped all the moisture as snow. The idea of getting five inches of precipitation, in the form of snow, in just a few hours, is not realistic.
The total storm snowfall record for Fargo is 24.5” in three days in January of 1989. For Grand Forks, it is 27.8” that fell over four days in March of 1966. That 1966 storm dropped 38” on Devils Lake. The water content of these storms was around two inches.
For our region, there are records of single-storm snowfalls approaching four feet from Gettysburg, S.D. and Washta, Iowa.