Hazardous Weather Outlook

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
408 AM CDT MON MAY 20 2013

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
210915-
WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE-
DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-
IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON-
408 AM CDT MON MAY 20 2013 /508 AM EDT MON MAY 20 2013/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS...
NORTHEAST ILLINOIS AND NORTHWEST INDIANA.

.DAY ONE...TODAY AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

  SCATTERED THUNDERSTORMS WHICH MAY PRODUCE...
   WIND GUSTS TO 65 MPH.
   ISOLATED TORNADOES.
   HAIL TO ONE INCH IN DIAMETER.
   LOCALLY HEAVY RAIN.
   CLOUD TO GROUND LIGHTNING.

  AREAS AFFECTED AND TIMING:

  THUNDERSTORMS WILL SLOWLY DEVELOP LATE THIS MORNING ACROSS
  CENTRAL ILLINOIS AND EASTERN IOWA...THEN LIFT NORTH AND EAST
  INTO NORTH CENTRAL ILLINOIS. ADDITIONAL THUNDERSTORMS ARE
  EXPECTED TO DEVELOP THIS AFTERNOON THROUGH TONIGHT ACROSS ALL OF
  NORTHERN ILLINOIS AND NORTHWEST INDIANA...WITH SOME OF THESE
  THUNDERSTORMS HAVING THE POTENTIAL TO BECOME SEVERE.

  DISCUSSION:

  AN UNSEASONABLY WARM AND TROPICAL LIKE AIRMASS HAS ARRIVED ACROSS
  THE REGION. THUNDERSTORMS FROM EARLY THIS MORNING HAVE
  DISSIPATED...HOWEVER THESE STORMS HAVE LEFT OLD BOUNDARIES ACROSS
  OVER NORTHERN ILLINOIS. THESE BOUNDARIES ARE EXPECTED TO SERVE AS
  A FOCAL POINT FOR THUNDERSTORM DEVELOPMENT LATER THIS MORNING.
  A WEAK LOW PRESSURE IS EXPECTED TO LIFT NORTH INTO CENTRAL ILLINOIS
  EARLY THIS AFTERNOON...ALLOWING SOUTHERLY WINDS TO BACK SLIGHTLY TO
  THE SOUTHEAST. THIS WILL PROVIDE ADDITIONAL FORCING AND LIFT INTO
  AN ALREADY UNSTABLE ENVIRONMENT. AS A RESULT THUNDERSTORMS ARE
  EXPECTED TO STRENGTHEN AND POSSIBLY BECOME SEVERE THIS AFTERNOON
  THROUGH TONIGHT. THE MAIN THREATS FROM SEVERE THUNDERSTORMS WILL
  BE DAMAGING WIND GUSTS AND HAIL TO ONE INCH IN DIAMETER.

  THE AIRMASS THAT WILL BE IN PLACE ACROSS THE OUTLOOK AREA HAS
  BEEN CONDUCIVE TO NOT ONLY PRODUCING WIND DAMAGE ACROSS THE
  CENTRAL PLAINS...BUT HAS PRODUCED TORNADOES. AS THE ATMOSPHERE
  BECOMES UNSTABLE THIS AFTERNOON THROUGH TONIGHT...LOW LEVEL
  CONDITIONS WILL BECOME FAVORABLE FOR A FEW ROTATING UPDRAFTS TO
  FORM IN SOME OF THE STRONGEST THUNDERSTORMS. THIS COULD LEAD TO
  THE DEVELOPMENT OF AN ISOLATED TORNADO ACROSS NORTHERN ILLINOIS
  AND NORTHWEST INDIANA.

  IN ADDITION TO THE SEVERE WEATHER CONCERNS WILL BE THE POTENTIAL
  FOR LOCALLY HEAVY RAINFALL. AS MENTIONED ABOVE...THE AIRMASS TODAY
  THROUGH TONIGHT WILL FEATURE A VERY MOIST ENVIRONMENT. AS A RESULT
  SOME OF THE THUNDERSTORMS HAVE THE POTENTIAL TO PRODUCE LOCALLY
  HEAVY RAINFALL...POSSIBLY TORRENTIAL DOWNPOURS. THIS COULD LEAD TO
  LOCALIZED FLOODING...ESPECIALLY IN LOW LYING AND POOR DRAINAGE AREAS.


.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

SCATTERED THUNDERSTORMS WILL BE POSSIBLE TUESDAY THROUGH WEDNESDAY
NIGHT...WITH THE POTENTIAL FOR SEVERE WEATHER TUESDAY ACROSS THE
ENTIRE AREA. THE MAIN SEVERE WEATHER THREATS WILL BE DAMAGING
WIND GUSTS AND LARGE HAIL.

HEAVY RAIN WILL ALSO BE POSSIBLE FROM ANY OF THE THUNDERSTORMS
THAT FORM TUESDAY NIGHT INTO WEDNESDAY MORNING. HEAVY RAINFALL COULD
LEAD TO LOCALIZED FLOODING...ESPECIALLY IN LOW LYING AND POOR
DRAINAGE AREAS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON THROUGH TONIGHT.

&&

$$