Monday afternoon snow - Second accumulating snowfall for some just this week

 

A second round (for some) of accumulating snow came down most of Monday afternoon, adding up to an inch on grassy surfaces in some locations. An inch of snow was reported in Mt. Carroll (Carroll) County, 0.5 inches was measured at 'Eyewitness News' and 0.3 inches in Poplar Grove (Boone County). Most of the snow has ended, although a few lingering flurries or spits of drizzle can't be ruled out through 8pm or 9pm.

Temperatures Monday morning warmed from the 30s, into the low 40s, but then quickly cooled as the precipitation started to shift east from Iowa. As the temperatures fell closer to freezing - 32 degrees - a transition over to all snow occurred. A few heavier snow bands were also experienced across much of the area, dropping visibility down to half a mile for a time during the afternoon.  

The snow that came down Monday wasn't the earliest measurable snow recorded in Rockford. That occurred back on October 3rd, 1951 when a TRACE of snow was reported. The record daily snowfall for today, October 19th, was 0.7 inches set back in 1989. Our record daily snow will still stand, but it is a good reminder that it can snow in October.

A quickly moving upper level disturbance is what brought the snow and rain to the Midwest and Great Lakes Monday. Even though temperatures were at, or above, freezing much of the afternoon we were still able to see the transition over to snow. This is because at the cloud layer temperatures were well below freezing. As the precipitation (snow) fell through the atmosphere it encountered a little bit of a dry layer just above the surface. That dry layer helped evaporate some of the snow. The snow that was able to make it through fell as either light rain or a mix as temperatures warmed near the surface. The snow that didn't make it evaporated within the dry

Kelly Everding - Freeport

layer. Since evaporation is a cooling process, it helped cool the surrounding air in the atmosphere. This, combined with the lift in the atmosphere from the disturbance moving through, allowed the air mass to cool just enough to cause the transition over to all snow. In fact, our temperatures in Rockford fell once the precipitation started - from 41 degrees just a little before 2pm down to 36 degrees, our current temperature. 

Skies will remain mostly cloudy through the night with temperatures right around freezing. The residual moisture on the pavement shouldn't cause too many issues late tonight or early Tuesday, but there could be a few isolated slick spots before the sun rises Tuesday.