Dew Points, Relative Humidity, & Snow

The snow which occurred overnight was a great performer in some places and not in others. The greatest snowfall occurred in Wisconsin where they have 8 to 12 inches or more. We received an inch or less. If you look at the maps from last night at 9 PM, you should notice several important features.

Temperatures were good enough to support snow here but it was colder in Wisconsin. They also had a much tighter temperature gradient. One problem we had were the dew points here were about the same as Wisconsin but were much further apart from the surface temperatures. That caused the snow to fall at the higher elevations in the atmosphere but not reach the ground.

Also noticeably different was the surface humidity was half as much as Wisconsin. They had 80% versus out 40%. Less moisture meant less snow potential. It is worth noting that the typical snowfall ratio provides 10-12 inches of snow for every inch of water. High ratios of 15-20 inches for each inch of water are a snow lovers dream. Last evening Wisconsin measured twice that with the NWS coming up with a 47 inch to one ratio. They even did the test twice to confirm it. Reports online said it was some of the biggest and fluffiest flakes every seen. Of course compaction came quick today and while there was no melting, snow levels are 1/2 of what there were at 4 or 5 AM.