MINNEAPOLIS (WCCO) — By the time the rain stops in Minnesota, the water will have come down for three days. So, how much would that be in snow? Good Question.
“That’s a tough thing to think about,” says Assistant State Climatologist Pete Boulay, adding it’s difficult for experts to give an exact answer to this question.
Meteorologists will give people an average ratio of 10 to 1, which means one inch of rainfall would equal 10 inches of snow. But, there are so many factors that could easily change that ratio.
The State Climatology Office and National Weather Service collect the snow from every storm in their gauge. They then melt it to see how much water is in the snow. For example, the Jan. 22 storm dropped 12.4 inches of snow, which equaled 1.03 inches of water.
“It’s not always 10 to 1,” says WCCO Chief Meteorologist Chris Shaffer. “That’s a pretty good estimate if you’re dealing with temperatures 28 degrees and warmer.”
If it gets colder, the ratio goes up. During the April 2018 blizzard, the temperatures were in the low 20s and the ratio was closer to 14 to 1. It can go as high as 20 to 1.
But, the chances of a 20-inch snow storm are far less likely than a 1-inch rainstorm because of the air masses that come with each of those events.
“A lot of it has to do with the systems,” says Shaffer. “In the cold of winter, a lot of our flow brings in those Alberta clippers, which is a drier air mass and there just isn’t as much moisture so you here us talking about a couple of inches.”
When the weather systems come up from the south, they bring in the warmer Gulf air holding more moisture.
Different temperatures will also bring in differently shaped snowflakes, which will determine the “fluffiness” of the snow.
“When it’s light, there’s more air content and that will allow it to stack up more,” says Shaffer.