Tuesday night rain/snow update: As of Tuesday morning

10:15am Update: Some of the morning models coming in and showing a little more of a southern track.  If that trend continues with further models, snow totals will be less for Tuesday night.


Light rain showers dotting the radar this morning in Wisconsin are having a hard time reaching the ground, but I wouldn't be surprised if a little drizzle occurs through the morning.

After that, the focus will shift to an approaching system moving out of the Rockies and passing south of northern Illinois by late tonight and early Wednesday.  As of right now, a Winter Weather Advisory is in effect for Ogle, Lee, DeKalb and Whiteside counties beginning at 10pm tonight and lasting through mid-morning Wednesday.  It is possible that the advisory will be shifted further north to include Rockford later today so we'll have to wait and see on that.  Right now, it still looks like the heaviest snow axis will fall between I-88 and I-80 with totals dropping off the closer you get to the Wisconsin/Illinois border.  And by heaviest, I mean totals between 3" to 6". 

As far as snow totals, there are a couple factors we need to keep in mind as we go through the night.  Afternoon temperatures have been warmer in recent days which has allowed the ground temperature to warm slightly.  This may lead to some melting snow initially when it falls.  Second, the storm track.  Any slight deviation in the storm track will shift that heavy snow axis either north or south.  Current storm track right now takes the low from the southern Plains through Missouri into southern Illinois late tonight and southern Indiana by Wednesday morning.  There will likely be a range in snow totals from north to south, with generally 1" to 3" falling along Highway 20 to 3" to 6" from Highway 38 and south.  This puts Rockford, Freeport, Winnebago, Belvidere, Byron, Leaf River, and Genoa right on the 3" line, with more falling south and less falling north.

Timing the precipitation: As I mentioned in the beginning, light showers are trying to develop along a cold front in the mid-levels of the atmosphere.  Some of that may be able to reach the surface through early afternoon. As colder air moves in from the north this afternoon, Wisconsin will experience more of a rain/snow mix through 4pm with a transition to snow after.  Northern Illinois will experience this transition after 5pm/6pm with a change over to all snow after 10pm/11pm.  The majority of the snow will fall into the overnight through 4am with the snow tapering off from west to east by 10am Wednesday morning.

Winds will increase from the Northeast tonight and remain fairly gusty through Wednesday afternoon.  The snow will have a little weight to it initially into the early overnight before cooler air moves in by Wednesday morning, so some blowing snow is possible by Wednesday morning.

We'll continue with further updates through the afternoon and evening.  Stay tuned!