Subtle changes in storm track and storm energy mean big differences in amount of snowfall

While it seems this next storm hasn't received as much of attention as the one last week, it has and will pack a punch for the Plains and Mississippi River Valley.  Winter Storm Watches (blue shading) continue for a portion of Northern Illinois but have been canceled for Rock and Walworth counties.  The reasoning - a slight shift south with the storm track was observed earlier this morning.

If you watched the forecast Monday morning, or even Sunday night for that matter, you already knew this was a very difficult storm to try and forecast and that a 'forecast bust' was possible regarding snowfall.  While the overall track of the storm has been fairly consistent amongst weather model data, subtle differences with the temperature profile, analysis of current snow cover and upper air features have caused me to gain a few more gray hairs this morning - and that continues here this afternoon!

Looking over some of the latest data that has come in this morning it looks like snowfall totals reaching anything higher than 3" may be hard to come by.  Temperatures at the surface Tuesday will remain very close to freezing and it's possible that we may even rise into the low to mid 30s now that we've been able to melt away some of the current snow.  As the snow melt continues the models have had a very hard time picking up on this feature because it's occurring on a very fine scale.  This means by the time the snow were to begin Tuesday models are forecasting surface temperatures slightly cooler than what they may actually end up being.  Also, with slightly warmer temperatures there is a chance that a wintry mix may occur at the onset during Tuesday afternoon before enough cooler air aloft wraps into the storm to allow a transition over to snow.  Low pressure will track out of Texas this afternoon and into Southern Illinois by Tuesday afternoon.  As of right now it appears as if the band of heaviest snow may occur just to the south and east of the Rockford area with Southeast Wisconsin, Northeast Illinois and maybe even around the Quad Cities receiving some of the higher snow totals.

The snow will fall Tuesday afternoon and it's possible a little lake enhancement with the northeast fetch off of Lake Michigan will cause higher snow totals from Milwauke to Kenosha to Waukegan to south of Chicago, but I think the further west you head from the lake the snow totals will decrease - significantly.  Right now I feel a forecast between 2"-4" is more likely with amounts closer to 4" in the highlighted areas stated above.  Regardless of snow amounts the winds will be strong Tuesday which will cause any snow that's falling, even if it's an inch or two, to blow around and reduce visibility.  Right now this snowfall doesn't look to be any bigger than the previous snowfalls we've experienced this winter season.  If anything does change between now and this evening we'll be sure to provide updates right here!