A WINTER STORM WATCH has been issued for all of southern Wisconsin and most of northern Illinois beginning either Monday evening or Tuesday morning. For Stephenson, Jo Daviess, Carroll, and Whiteside counties the watch will begin at 6pm Monday and last through Wednesday morning. For Green, Rock, Walworth, Winnebago, Boone, McHenry, Ogle, Lee, and DeKalb counties the WATCH goes into effect Tuesday morning and will last through Wednesday morning.
While some of the finer details with the winter storm are becoming a little clearer, the storm is still 24-36 hours away and subtle shifts and changes are likely to occur during that time. But here are some of the key messages we want to get out regarding impacts of the incoming snow:
The snow event will arrive in two rounds, with the first coming in late Monday evening and the second during the day Tuesday. Both rounds will feature a heavy and wet snow with temperatures in the low 30s. Monday night’s snowfall will cause some impacts to Tuesday morning’s commute, but greater impacts are possible for Tuesday afternoon and evening. It’s during this time that a very heavy and wet snow will fall likely causing roads to become snow and slush covered throughout the day, reducing visibility, and making travel difficult to dangerous at times as the day wears on.
Low pressure currently over the Southwest will lift to the northeast through Plains Monday, and into the Great Lakes Tuesday evening. The current track of the low takes it from near St. Louis, MO Tuesday morning towards Chicago and northwest Indiana by Tuesday late afternoon and evening. This type of track does put areas of north-central and northwest Illinois, along with southern Wisconsin, in the favored location for heavy snow and high totals. But the absence of a cold air mass with the storm does raise some questions as to where exactly the rain/snow line sets up, which could ultimately impact totals overall. Over the last couple of days, the storm track has shifted some to the northwest, which pushes the freezing line closer to northwest Indiana and northeast Illinois. However, the heaviest snow usually falls just north of where the surface low tracks – placing areas from the Quad Cities up through Rockford in line for heavy snow. Temperatures during this time will be borderline freezing. In fact, temperatures will likely remain above freezing during the entire event.
The snow to liquid ratio is likely to be lower than the average 10:1 – and probably closer to 8:1. This indicates that the snow will have a lot of moisture with it. Great for making snowballs and snowmen, but very sloppy and slushy. A heavy and wet snow doesn’t accumulate as well as a drier and lighter snow. However, being just north of the surface low track the amount of lift in the atmosphere may be able to overcome the lower snow to liquid ratios by producing high snowfall rates – over an inch per hour – causing the snow to accumulate rather quickly throughout the day. If these higher snowfall rates do occur, travel would become very difficult from mid to late morning Tuesday through the evening.
Another key element to this winter storm is the rain/snow line. Should the track move a little further to the northwest tonight and Monday, that line would be pushed further inland and possibly impact areas to the east and southeast of Rockford from McHenry County down through DeKalb and parts of Lee County. There is likely to be a very sharp gradient of where exactly we see all snow, and heavy snow, to where we end up seeing a mix and lower snowfall totals. This gradient will become better defined over the next 12-24 hours.
As of Sunday evening, our preliminary snowfall forecast is calling for between 4-8 inches of snow across most of the region, with a snowfall gradient lining up from parts of McHenry County through southern DeKalb County. The greatest impacts are likely to occur from southern Wisconsin through most of north-central and northwest Illinois Tuesday with regards to snow accumulation and wind. And while there isn’t a high chance for this, sporadic power outages are possible given the heavy nature of the snow and gusty winds Tuesday.
We will continue to monitor the latest trends and track of this storm and provide updates as needed. It may be a good idea to think about adjusting travel plans, especially Tuesday, if the current forecast remains on track. Most of the snow will be wrapping up Tuesday night with only a few flurries lasting into Wednesday morning.
A relatively snow-free winter is coming to an end this week as the city prepares for winter storms headed toward Chicagoland.
According to WGN Meteorologist Tom Skilling, multiple storm systems are likely to impact Chicago in the days ahead, followed by a decidedly colder pattern with arctic air arriving over the coming weekend and into next week.
When Is The 1st Round Of Snow Expected in Chicago, Illinois & NW Indiana?
Skilling said a first round of accumulating snow is likely to develop later Monday night into Tuesday morning across the Chicago area before the storm center sweeps from the Texas panhandle up and nearly directly over the city.
Snow may begin flying in Chicago between 9 p.m. and midnight on Monday night and continue from 5 a.m. to 7 a.m. on Tuesday morning.
Meteorologist Mike Janssen said upwards of six inches of snow are possible on Tuesday and into Tuesday night. Snowfall rates around 1″ per hour are possible and winds could gust >30 mph Tuesday night.
By Tuesday morning precip is likely to have transitioned to a wintry mix in the city while snow continues to the west toward, and just west of, the Fox Valley into DeKalb, from western Lake into McHenry and Boone counties in Illinois, west into the Rockford/Beloit/Belvidere and Janesville areas, and north into Lake Geneva and other sections of southeast Wisconsin.
Skilling said areas west of Chicago could see some of the heaviest snow accumulations, but since the onset of the storm’s precipitation is more than a day away, projections could change.
The significant storm system is expected to move out by early Wednesday.
When Is The Second Round Of Snow Expected?
According to Skilling, the second round of winter weather could approach the Chicago area later Friday, Friday night and Saturday.
Skilling said there are even hints that Chicago, which is likely to be more deeply in colder air by then, could end up with more snow out of the second system than the first one, but is far too early for reliable snowfall tallies.
What Areas Are Under Winter Storm Watches?
Several Winter Storm Watches are set to go into effect on Monday and Tuesday as heavy snow and wind move into Chicagoland.
The National Weather Service (NWS) has issued a Winter Storm Watch that is set to go into effect at 6 p.m. on Tuesday afternoon for Boone, De Kalb and McHenry counties until 3 a.m. on Wednesday.
Chicago isn’t alone, advisories for winter weather are out across all or portions of 19 states and the storm’s warm sector, toward the Gulf Coast and the Southeast U.S., is threatened with a severe weather outbreak, Skilling said.
By Tom Skilling, Mike Janssen, Gabriel Castillo and Candice King
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