Once-in-a-lifetime snow?

The weather we've worried about for a couple of days looks set to hit this afternoon:

Four days of computer forecasts of this storm, including multiple runs off 7 models, are putting the developing system on a more northerly track while generating water equivalent precipitation of around 30 mm. To convert that to snow, calculations have to be made of how snowflakes are likely to develop in the storm given a snow/water ratio predicted to be 15 to 1 Tuesday evening. [This means 450 mm of snow. —ed.]

As expected, Lake Michigan may contribute an additional 75 to 175 mm to the system in lakeside counties

The National Weather Service warns:

A BLIZZARD WARNING REMAINS IN EFFECT FROM 3 PM THIS AFTERNOON TO
3 PM CST WEDNESDAY.

* TIMING...ACCUMULATING SNOW WILL DEVELOP AROUND THE INTERSTATE 80
  CORRIDOR DURING THE EARLY TO MID AFTERNOON...SPREADING NORTH TO
  THE WISCONSIN STATE LINE BY MID TO LATE AFTERNOON. THE MOST
  SIGNIFICANT SNOW MAY COME IN A COUPLE OF WAVES...WITH THE FIRST
  WAVE LATE THIS AFTERNOON INTO EARLY THIS EVENING...FOLLOWED BY A
  SECOND WAVE OF INTENSE SNOW LATER THIS EVENING INTO THE
  OVERNIGHT. ACCUMULATING LAKE EFFECT SNOW SHOWERS WILL CONTINUE
  OVER NORTHEAST ILLINOIS WEDNESDAY MORNING...SPREADING INTO
  NORTHWEST INDIANA WEDNESDAY AFTERNOON.

* ACCUMULATIONS...SNOW WILL BE HEAVY AT TIMES WITH ACCUMULATION
  RATES OF 1 TO 2 INCHES PER HOUR LIKELY. STORM TOTAL SNOWFALL OF
  10 TO 18 INCHES IS LIKELY TOWARD ROCKFORD AND DIXON. THE
  HEAVIEST SNOWFALL TOTALS ARE LIKELY DOWNWIND OF LAKE MICHIGAN IN
  THE CHICAGO METROPOLITAN AREA INTO NORTHWEST INDIANA WHERE 12 TO
  20 INCHES OF SNOW IS LIKELY...WITH ISOLATED AMOUNTS OF AROUND 2
  FEET POSSIBLE.

* WINDS...NORTHEAST WINDS WILL INCREASE TO 20 TO 35 MPH BY LATE
  THIS AFTERNOON. WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE BY
  EVENING WITH GUSTS OF 40 TO 50 MPH LIKELY TONIGHT. EVEN STRONGER
  WINDS ARE LIKELY NEAR THE IMMEDIATE LAKESHORE WITH SUSTAINED
  WINDS OF 30 TO 40 MPH WITH GUSTS BETWEEN 50 AND 60 MPH.

The Daily Parker will have updates and photos as conditions warrant.