ASK TOM: How long does snow have to stay on the ground to be measurable?

Dear Tom,

How long does snow have to stay on the ground to be measurable? Let’s say it snows 0.2 inch, then totally melts in an hour. Then the same thing happens again. Is the total snow 0.4 inch?

– Ed Kozak, Chicago

 

Dear Ed,

It is. The total snowfall in that situation would be 0.4 inch. Frank Wachowski, a familiar name here, wears many hats, but none more authoritatively than “premiere weather observer.” Wachowski tells us there are no duration criteria for accumulated snow. Total snowfall is reported as the sum of all snow accumulations, regardless of whether the snow sticks around. However, repetitious snow-and-melt, snow-and-melt situations are not common occurrences here. Wachowski noted that snow that falls on wet ground but never accumulates is reported as “trace — melted as it fell.”