WINTER STORM WARNING goes into effect 3 a.m. FRIDAY and runs through NOON Saturday…

Snow is likely to begin in the city an hour either side of 4 a.m. CST Friday morning

BOTH FRIDAY RUSH HOURS will be impacted

Wind gusts will build to 30 to 40 mph Friday and to 50 mph at times, especially open areas Friday night

The warmth of Lake Michigan may limit accumulations lakeside area compared to the rest of the area. But it appears 4 to 9″ accumulations may be widespread and that amounts will drop off to the south of Chicago while coming in heaviest west and north of the city

One forecast WILDCARD–the potential snow may mix with or change to rain in roughly the 9am to 3pm time frame. There isn’t universal agreement among the models. But this may affect accumulations—and that is most likely to occur south and southeast of the city where a switch to rain or a wintry mix appears more likely.

Blowing of snow amid falling temps and strengthening winds could create issues, especially Friday night in Saturday morning on open stretches of north/south roads

A BITTERLY COLD ARCTIC OUTBREAK settles in over the weekend with temps falling from the low or mid 20s as Saturday opens to below zero by Sunday morning.

Wind chills will drop SUB-ZERO Saturday evening and remain SUB-ZERO until later Wednesday—a run of nearly 4 consecutive days.

 IF ONE THING IS CLEAR FROM THE MODELING WE’RE SEEING ON THIS STORM—it will hit in stages—with snow commencing in the city around 4am Friday morning and becoming potentially heavy into the morning rush hour (roughly 6 to 9am)—then there’s the suggest we may go through a “wintry mix” stage roughly 9 to 3pm—but may see a transition back to snow–and an ensemble model run by the NWS Storm Prediction Center–has a transition back to snow in the city in the late afternoon and evening, which would coincide with the FRIDAY EVENING COMMUTE PERIOD.  Snow will then fall amid howling NE shifting NW winds Friday night with gusts to 50 mph not out of the question.

FOR NOW–Here are some probabilities generated by the NWS Weather Prediction Center’s WINTER ENSEMBLE MODEL, which factors projections from 28 model fcsts:

HERE ARE CURRENT FORECAST PROBABILITIES FOR THE FOLLOWING AMOUNTS OF SNOW “CENTERED ON CHICAGO PROPER”

Chance of this storm generating:

  • 2″ or more  97%
  • 4″ or more 90%
  • 6″ or more 75%
  • 8″ or more 60%
  • 12″ or more 29%

Note that heaviest amounts are to occur inland to the west and north of Chicago and there, probabilities on the higher end totals will be higher. CONVERSELY—if you’re south—in Morris, Kankakee and Rensselaer, IN as an example, accumulations are likely to be reduced by the switch to a wintry mix or rain for a time Friday.  Precip will shift back to snow late Friday and/or Friday night.

Latest warnings and watches from the National Weather Service.

HERE’S MY LATEST CHICAGO METRO FORECAST (1/11/2024):

…WINTER STORM WARNING from 3am CST FRIDAY to NOON CST SATURDAY…..

TONIGHT: Clouds return with snow reaching the city an hour or two either side of 4am CST Friday morning—arriving soonest south and west of the city. Wind shift easterly and increase 14 to 30 mph by daybreak. Low 28.

FRIDAY: Snowy and windy.  Snow—potentially heavy as the day gets underway, may mix with rain for a time mid-morning  into mid-afternoon but will likely switch back to snow for the late afternoon and evening commute period.  Wind gusts build to 30 to 40 mph. High 34. 

FRIDAY NIGHT: Snowy, very windy and turning colder. Blowing snow may occur in open areas impacting north/south thoroughfares most significantly. Total area snow accumulations: 4 to 9 inches. Winds off 39-deg Lake Michigan may result in accumulation reduction along and near the shoreline.  Low 23.

SATURDAY: Quite windy and colder with 30 to 45 mp westerly wind gusts and falling temps.  A morning high of 23—but reading falling into the teens.

SATURDAY NIGHT: Sporadic flurries, windy and becoming bitterly cold. Low 2-below by morning with wind chills dropped to 15 to 22 below by daybreak.

SUNDAY: Bitterly cold. Cloudy spells and windy with possible flurries from time to time. High 7-above—but daytime wind chills 10 to 20-below.

MONDAY THROUGH WEDNESDAY: Arctic air’s in control—though temps will rebound modestly Wed afternoon. Partly cloudy, occasionally cloudy, blustery and cold. High Monday 5-above. Tuesday’s high 7-above.  High Wednesday 18.