Accumulating snow will be likely late tomorrow and into tomorrow night/Friday morning. Admittedly, this is tricky forecast with narrow swath of heavy snow and high snow accumulations possible. The trick is figuring out where the heavy snow will fall, which at the moment looks like will be mainly north of I-74.
Before we see any snow falling tomorrow, we'll likely have some rain or a wintry mix moving in as early as the afternoon. That will eventually change to all snow as we head into late tomorrow evening and tomorrow night.
Snow showers should taper off as we head into Friday morning, and any lingering precipitation on Friday could gradually change to a light wintry mix or rain as temperatures rise through the 30s.
As of writing this (3:50 PM on Wednesday afternoon), a Winter Storm Watch has been issued for some areas north of I-74. This is where the heaviest snow will likely fall.
I am expected a very sharp cut-off between areas of moderate and minimal snowfall accumulation. It may be possible for some areas to see around 4" of snow, with locations 25-50 miles south seeing less than 1".
With that in mind, here is what I am expecting.
Keep in mind that the ranges represent a range of the low and high amounts of snow possible.
So what could go wrong with this forecast?
Like I mentioned above, the heaviest snow will likely fall in a relatively narrow band. If that shifts 50 miles north or south, the high totals will shift with it. For now, forecast models have a decent consensus of where that band will be, but again any small changes to that location will have a big impact on the forecast.
In addition, temperatures not just at the surface but also about a mile up in the atmosphere will be hovering close freezing. A change of only a couple of degrees lower could mean an earlier transition to snow, while only a degree or two higher could mean more rain.
We'll tweak this snow map as needed as new forecast data comes in. You can get the latest forecasts online, on social media, and by downloading our Heart of Illinois ABC app.