Second storm in a week; this one windier and wetter/snowier than its predecessor


The Chicago area prepares for a rendezvous with its 2nd winter storm in less than a week—a system which has a real chance of laying down the season’s most significant snowfall to date. Howling winds will be among the latest storm’s calling cards.



Powerhouse 40+ mph northeasterly wind gusts to rake the Chicago area



This system dwarfs last Thursday evening’s in terms of its size and wind production. Gusts topping 40 mph from the northeast lock in Tuesday and Tuesday night.



Our hi-res RPM model is generating some 50 mph gusts on Chicago’s lakeshore from midday forward on Tuesday.



Precipitation is to arrive during the morning, when rain or a wintry rain/sleet mix commences, spreading northward across the metro area. Areas south of Chicago will get in on precipitation earlier.



All eyes on a potential shift to heavy snow which could make for a miserable evening rush hour



The transition to potentially heavy snow, predicted to take place mid and late afternoon, may prove incredibly ill-timed. Such a development would contribute to travel-hampering weather conditions during Tuesday afternoon and evening’s busy commute period.



Heavy snow riding powerful 40+ mph wind gusts could lead to near blizzard conditions, so the timing of the switch from liquid to crystalline-form could prove critical to late-day travel times.



Storm’s potential snowfall estimated to range from 3-7 inches



Our guidance suite—the collection of computer model estimates and other snow forecast tools employed as part of our forecast preparation process—-supports a prediction of 3 to 7 inch accumulations by late Tuesday night—snow which is likely to fall at times horizontally in the high winds which are predicted.  Blowing and drifting of the snow may become a serious issue. What’s more, it looks as if the snow which accumulates will be especially wet and of particularly high density—what’s referred to as “heart attack” snow. Snow shoveling will have to be approached with care.



Historic snows hit the southern Plains; Amarillo buried beneath 19″ of snow; 3-6 ft. drifts reported!



JD Carlson of the Oklahoma Mesonet reported to us late Monday that 22 inches of snow had fallen just west of Alva, Okla. near the Kansas border. The snow was generated by the same storm which blanketed Amarillo, Texas Monday beneath 19 new inches of snow—that city’s second highest calendar day snowfall on record. High winds produced snow drifts up to 3 to 6 feet in height.



Flights cancelled as storm bears down on the area



United Airlines late Monday began canceling flights out Chicago scheduled for Tuesday afternoon and evening in anticipation of the deteriorating weather conditions. It would be wise to check with airlines before heading out to the airport Tuesday afternoon or night.



Winds roaring off Lake Michigan could boost lakeside snow totals



An area of higher snowfall totals predicted for northeast IL on the current  “RPM” and Weather Service “WRF” computer model runs appears the product of what’s known in the weather forecast community as “wind convergence” in the area adjacent to the Lake Michigan shoreline.



That higher totals may occur in lakeside counties of northeast Illinois and southeast Wisconsin is not surprising.



The powerful easterly winds predicted to roar into Chicago Tuesday will come off the lake “nearly geostrophic” (i.e. friction free). Their interaction with land leads is to produce frictional drag as they grind against features of the terrain, trees, buildings, etc.  It’s a development likely to slow wind velocities over land.



This leads to the “convergence” or “pile-up” of air over Lake Michigan’s shoreline counties as the faster-moving air coming in off the lake converges with the slower-moving land-based winds. The resulting pile-up of air enhances “lift” (the upward motion of air) which leads to cooling.   This, in turn, increases precipitation rates, producing higher potential snowfall and precip tallies.


Storm’s generous 1″+ water-equivalent precip not completely unwelcome given recent drought conditions



No matter matter what form the precipitation in Tuesday’s storm takes, we have model estimates of more than 1″ of water-equivalent precipitation falling across the Chicago area. This continues the trend of above-normal rain and snowfall observed here since Jan. 27—a situation which has led to the highest Jan. 27-Feb. 25 precip tallies here in 126 years and the 2nd highest on record since observations began in 1871. That’s not all bad news in an area which has been wracked by drought!