Severe weather possible today.

  THUNDERSTORMS...SOME MAY PRODUCE:
   HAIL TO THE SIZE OF QUARTERS AND POSSIBLY ISOLATED GOLF BALLS.
   DAMAGING WINDS.
   HEAVY RAINFALL.
   FREQUENT LIGHTNING.

LOW PRESSURE WILL MOVE EASTWARD ACROSS NORTHERN ILLINOIS AND
  NORTHWEST INDIANA TODAY BRINGING A COLD FRONT THROUGH THE AREA
  WITH IT. VERY WARM AND MOIST AIR WILL SURGE NORTHWARD AS A WARM
  FRONT MOVES INTO THE AREA AHEAD OF THE LOW THIS MORNING.
  MODERATE INSTABILITY WILL RESULT BY AFTERNOON ACROSS MUCH OF
  NORTHERN ILLINOIS AND NORTHWEST INDIANA WITH THE COLD FRONT AND
  AN ATTENDANT UPPER LEVEL DISTURBANCE POTENTIALLY TRIGGERING
  THUNDERSTORM DEVELOPMENT. THE PRIMARY AREA FOR DEVELOPMENT IS
  EXPECTED TO BE ALONG AND SOUTH OF THE INTERSTATE 80 CORRIDOR
  THOUGH SOME ELEVATED THUNDERSTORMS MAY DEVELOP AS FAR NORTH AS
  THE WISCONSIN BORDER. IT IS POSSIBLE THAT STORMS MAY NOT DEVELOP
  UNTIL CLOSER TO EVENING WHICH MAY PUSH THE THREAT FURTHER SOUTH.
  DEEP LAYER WIND SHEAR WILL BE RATHER WEAK SO STORMS MAY PULSE UP
  AND DOWN IN INTENSITY WHILE ORGANIZING INTO CLUSTERS. PROVIDED
  STORMS DO DEVELOP...HAIL...TO THE SIZE OF QUARTERS AND POSSIBLY
  GOLF BALLS...AND DAMAGING WINDS WILL BE THE MAIN SEVERE THREATS.
  HEAVY RAINFALL AND FREQUENT LIGHTNING WILL ALSO ACCOMPANY ANY
  STORMS.