Fri-Sat December 11th-12th Snow Event Update #2

(11:45AM - 12/10/20) We are continuing to keep a close eye on a weather system that will be impacting the Midwest and much of Illinois Friday afternoon through a good chunk of the day on Friday and one that still looks like it will bring a swath of accumulating snow to the region.

Our weather system of interest this morning is still out over the Pacific Ocean off the west coast of the U.S. but continues to make steady progress east and southeast and will eventually come ashore later today. This should help numerical model guidance continue to get a better idea of how this system will play out across the Midwest. Drawn on the image below is the rough track this system will take between this morning and Saturday afternoon. 

As things stand now, an area of low pressure will steadily come northeast from Friday afternoon through Saturday afternoon, steadily strengthening as it does so. Much of Illinois will see precipitation in the form of rain given temperatures above freezing. However, we continue to watch this closely as there still looks to be a swath of accumulating snow on the northwest and north side of this weather system as you can see below in the animation. 

By early Saturday morning, model ensemble guidance continues to show some disagreement on the exact placement of the area of low pressure across the state and this is leading to some difficulty pinning down the exact area of potential accumulating snows. A further south track would bring the above swath of snow further south into northern Illinois where a further north track would mean more of the snow ending up across Iowa and Wisconsin and not Illinois. 

Snow could develop across portions of far northwest and northern Illinois as early as Friday evening and then continue through Saturday afternoon and possibly the evening hours across those areas. Surface temperatures will again be on the marginal side but with the threat of heavier snowfall rates, there could be some localized heavy amounts. 

Below is our latest thinking on snowfall accumulations...