By Meteorologist Richard Koeneman
Walt Kelly (1913-1973), creator of the comic strip “Pogo,” once remarked, “What’s good about March? Well, for one thing, it keeps February and April apart.” Kelly understood that March, more than any other month, can manifest the temperature and weather characteristics of both winter and summer.
This year, Chicago’s March is off to a decidedly tumultuous start, and, following a cold and snowy winter, the city is approaching a snowfall milestone. The overnight storm that delivered thunderstorms and heavy, wind-driven snow has carried this snow season’s cumulative snowfall to within striking distance of the city’s all-time snowfall record: 89.7 inches during the winter of 1978-79. As of March 11, the season snow total stood officially at 75.5 inches as measured at O’Hare International Airport (and 79.2 inches at Midway Airport).
As the weather warms this spring, we will begin to have extended periods with above-freezing temperatures. What is the longest period the city has gone without dropping to 32 degrees or lower?
— John Hastings, Niles
Chicago’s growing season — the period between the last freeze in spring and the first freeze in autumn —typically runs about six months, from mid-April to mid- or late October. In 1931, however, the last spring freeze was April 2 and the first autumn freeze was delayed until Nov. 24, a record 236 days later. The exceptionally late autumnal freeze was a direct result of the location of the city’s official thermometer on the University of Chicago campus, near the mild water of Lake Michigan. At Midway Airport, the first 32-degree fall reading occurred more than three weeks earlier, on Nov. 1.
A look at the latest WGN in-house RPM model shows the rain changing to snow in the next few hours changing to heavy snow in the post midnight hours The heavy wet snow is expected to accumulate rapidly overnight with total accumulation ranging from 1 to 4 inches north and west to the city to 4 to 8 inches in areas from the city and south. Some of the snow will be accompanied by thunder and will fall intensely with accumulation of 1 to 2 inch an hour possible.
Travel conditions will quickly deteriorate after the snow begins and strong gusty northeast winds will cause some blowing and drifting of the snow. The snow is expected to taper to flurries by early Wednesday morning but cause problems for the morning commute.
Winter storm warninga are posted for much of the Chicago Metro area with the exception of areas well north and northwest of the city.
Lemont- Pea size hail at 127th and Archer at 9:13pm
The opening round of tonight winter storm is spreading into the Chicago area this evening in liquid form as a band of showers and thunderstorms, some with small hail, arrive. However, to the north across far southern Wisconsin the precipitation is changing over to snow.
At 9pm snow or sleet was being reported at Racine, Milwaukee, Burlington and Waukesha. As colder air filters into the area, coupled with cooling from evaporation and cooling from increasing vertical motion, the precipitation in the Chicago area should change over to snow later this evening north of the city and in the post midnight hours from the city and areas south.
At 8:30PM CDT numerous showers and a few thunderstorms have developed in the past hour back to the west and southwest of Chicago (see current weather radar above). The showers are moving east-northeast, and should reach the Chicago area within the next hour or so. Some will produce pea-size hail. So far this evening pea to marble-size hail has been reported at Morris, Mendota and Princeton and Galva.
At the same time temperatures have fallen into the mid to upper 30s area-wide as strong northeast winds continue to pull cold air off the icy cold Lake Michigan. Chicago-area dew-points have settled into the upper 20s to lower 30s for the most part.
So the stage is set for a cold rain to settle into our area with a changeover to sleet and then a wet snow still looking viable later this evening.
8:15PM CDT temperatures
Update 7:25PM CDT..
As of 7PM CDT temperatures at O’Hare and Midway had fallen 11-degrees from their afternoon highs – to 38 and 39-degrees respectively. Northerly Island and Waukegan had dropped to 35-degrees. Most of the area temperatures were in the mid to upper 30s.
Note on the weather radar picture above a narrow band of showers was approaching the Ottawa area moving east-northeast and widely scattered areas of light rain were moving out of Wisconsin into northern Illinois.
Note 7:15PM CDT temperatures..
At 6PM CDT northeast winds off the cold waters and ice on lake Michigan were gusting to 3ern illinois.0 miles an hour at O’Hare and 28 miles an hour at Midway Airports where temperatures had dropped to 41 and 40-degrees respectively.
The Chicago area temperatures at 6:15PM CDT displayed below indicate Chicago-area readings have dropped into the upper 30s at several locations. Temperatures will continue to fall into the middle and lower 30s as the evening goes on – and the window of rain changing over to snow will be shortened considerably as the cool-down occurs this evening.