Major snowfall on the way

Update 3:30pm: I am going to keep the 3-6 inch swath going for the Rockford metro, but hike up McHenry and Lake Cos. into the 6"+ range. Should thunder be heard, we will go above 6 inches here in Rockford. Should we be mixed with rain for a time, totals will be lower. Areas south of I-88 may see a slushy inch with a higher threat of heavy rain/thunderstorms. -ERIC




Update 3:00pm: We're pretty much staying on target with this system. It appears the snow will begin shortly after midnight and ramp up during the 2-6am timeframe. Thunder appears quite possible as upward forcing reaches its peak during the predawn hours. With the convective nature of this system, extremely heavy snow is possible...perhaps in the 2-3 inch per hour range. As mentioned earlier, we have a few things to consider this time of year: our ground is above freezing to a depth of three inches. Falling snow will have to overcome melting from ground. Another thing is the fact that this may not all be snow. Should we transition over to rain at any given time, snowfall totals will be significantly impacted. Of all of the snow systems thus far this winter (and early spring) this one is the trickiest! Will hold onto a solid 3-6 inch forecast for North-Central Illinois, but will be highlighting the higher end of that range. A few areas in McHenry and Lake County may see a 8-9 inch total...and if we can maintain the snow during times of thunder, a few 6"+ totals will be seen north of US20 in Boone, Winnebago, and Stephenson County. Snow-water ratios will be around 9:1 range meaning this is prime heart attack snow. Please do not shovel this snow if you have a health condition! More to come. -ERIC

Update 12:30pm: The latest model guidance continues to show a pretty potent storm impacting us on Friday. It is still cranking out a lot of precipitation, but it appears the end of the storm is being bumped up a bit. I'm looking at the precipitation (mostly snow) to start around 3am. As depicted by the graphic to the left, it will be the heaviest during the morning hours as the low spins just to our south. It will lighten up a bit during the afternoon, and taper off during the evening hours. The axis of heaviest snow appears to be on a line from Monroe, WI to Rockford and on through Chicago. Even though wind speeds tomorrow will range between 15-25 mph out of the east, blowing and drifting snow won't be a big deal because of how heavy and wet the snow will be.

Update 11:05am: The National Weather Service in Chicago will be upgrading the watch to a warning shortly for all of northern Illinois.

Update 5am: The WINTER STORM WATCH (light blue) has been extended to include Whiteside & Lee Counties. Also, the National Weather Service office in the Quad Cities has taken the liberty to upgrade the watch to a WINTER STORM WARNING (red) for Jo Daviess, Stephenson, and Carroll County. The rest of the region will probably be upgraded to a warning this afternoon. No doubt the entire viewing area is going to run into poor travel conditions on Friday.

Original Post: A WINTER STORM WATCH is in place for the majority of the viewing area. The only counties not included in this watch are Whiteside and Lee Counties. Simply put, if you have holiday travel plans on Friday... you might want to move them up to Thursday night.

This storm system will start kicking out precipitation shortly after midnight Friday morning. If you live along Interstate 88 you are going to encounter a mix of rain and snow, but if you live north of Highway 20 it appears as though the majority of the precipitation will come in the frozen form. There is a lot of moisture to work with in this storm system, so some fairly hefty snowfall totals by March standards are quite possible. At this point, the highest totals appear to be along the Wisconsin/Illinois border. The snow that does fall is going to be the heavy and wet variety. Temperatures during the storm are set to be sitting in the low to mid-30s. Because of this, some of the snow will be melting as Friday progresses, which could limit some of the higher snowfall totals. This is going to be an all day event with the precipitation finally winding down early Saturday morning. -ADAM