Alert archive / Illinois / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 129, NWS Chicago, IL

July 24, 20116 counties in Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jul 24, 2011, 6:44 AM CDT for 6 counties in Illinois. It was in force for 47 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 24, 2011, 6:44 AM CDT (11:44 UTC)
Expired: Jul 24, 2011, 7:31 AM CDT
In force: 47 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.5 in
Wind: 60.0 mph

Counties DeKalb County, IL, Grundy County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL

The radar

The Chicago radar (KLOT), 56 km from the middle of the area, began a volume at 11:46 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 11.7 hours before the alert went out and 146 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 2467 J/kg
Mixed-layer CIN: -38 J/kg
Mixed-layer LCL: 1436 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 82 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.7

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 24, 4:27 AM CDT, 2 hours 17 minutes earlier.

Area forecast discussion, Jul 24, 4:27 AM CDT, 2 hours 17 minutes before

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Hazardous weather outlook, Jul 24, 4:21 AM CDT, 2 hours 23 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
421 AM CDT SUN JUL 24 2011

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
250930-
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-
421 AM CDT SUN JUL 24 2011 /521 AM EDT SUN JUL 24 2011/

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

.DAY ONE...TODAY AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

  THUNDERSTORMS...SOME MAY PRODUCE:

   HEAVY RAINFALL WITH FLASH FLOODING.
   FREQUENT LIGHTNING.
   DAMAGING WINDS IN EXCESS OF 60 MPH.

  OPPRESSIVE HEAT AND HUMIDITY.

  AREAS AFFECTED AND TIMING:

   THUNDERSTORMS ALONG AND AHEAD OF A COLD FRONT WILL MOVE INTO
   NORTHWESTERN ILLINOIS THIS MORNING AND THEN SPREAD SLOWLY SOUTH
   AND EAST INTO EAST-CENTRAL ILLINOIS AND NORTHWESTERN INDIANA
   LATER TODAY.

   THE DANGEROUS HEAT AND HUMIDITY WILL CONTINUE...ESPECIALLY
   SOUTH OF INTERSTATE 80.

  DISCUSSION:

   THUNDERSTORMS ARE EXPECTED TO BRING MORE HEAVY RAINFALL TO
   NORTHERN ILLINOIS AND NORTHWESTERN INDIANA TODAY. SINCE THE
   GROUND IS SATURATED AND AREA RIVERS SWOLLEN FROM THE VERY HEAVY
   RAINFALL OF THE PAST FEW DAYS...IT WILL NOT TAKE VERY MUCH
   ADDITIONAL RAINFALL TO BRING A RISK OF ADDITIONAL FLASH
   FLOODING TO THE AREA. WITH A VERY MOIST AIRMASS IN PLACE AND
   LITTLE PUSH BEHIND THE APPROACHING COLD FRONT...THUNDERSTORMS
   WILL BE EFFICIENT RAIN PRODUCERS AND HEAVY RAINFALL IS LIKELY.
   THUS THE FLASH FLOOD WATCH WILL REMAIN IN EFFECT FOR PORTIONS
   OF THE AREA GENERALLY NORTH OF INTERSTATE 80.

   LOCATIONS ON THE DES PLAINES AND DU PAGE RIVERS WILL REMAIN
   ABOVE FLOOD STAGE THROUGH TONIGHT.

   HEAT INDEX VALUES ARE EXPECTED TO RISE TO 110 TO 115 DEGREES
   THIS AFTERNOON FOR LOCATIONS SOUTH OF THE ILLINOIS AND KANKAKEE
   RIVERS

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS WEDNESDAY
THROUGH SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY TODAY...ESPECIALLY FOR FLASH
FLOODING AND STRONG...DAMAGING WINDS.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ740>745-250930-
WINTHROP HARBOR TO WILMETTE HARBOR-
WILMETTE HARBOR TO NORTHERLY ISLAND-
NORTHERLY ISLAND TO CALUMET HARBOR-CALUMET HARBOR TO GARY-
GARY TO BURNS HARBOR-BURNS HARBOR TO MICHIGAN CITY-
421 AM CDT SUN JUL 24 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE
WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS TODAY CAUSING WIND GUSTS IN
EXCESS OF 35 KNOTS AND FREQUENT LIGHTNING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS WEDNESDAY THROUGH
FRIDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-250930-
LAKE MICHIGAN FROM MICHIGAN CITY IN TO ST. JOSEPH MI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM SEUL CHOIX POINT TO ROCK ISLAND PASSAGE 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN SOUTH OF A LINE FROM SEUL CHOIX POINT TO THE
MACKINAC BRIDGE AND NORTH OF A LINE FROM CHARLEVOIX MI TO SOUTH
FOX ISLAND 5 NM OFFSHORE-
LAKE MICHIGAN FROM CHARLEVOIX TO POINT BETSIE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM POINT BETSIE TO MANISTEE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM ROCK ISLAND PASSAGE TO STURGEON BAY WI-
LAKE MICHIGAN FROM STURGEON BAY TO TWO RIVERS WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM TWO RIVERS TO SHEBOYGAN WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM SHEBOYGAN TO PORT WASHINGTON WI 5 NM OFFSHORE
TO MID LAKE-
LAKE MICHIGAN FROM PORT WASHINGTON TO NORTH POINT LIGHT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM NORTH POINT LIGHT TO WIND POINT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WIND POINT WI TO WINTHROP HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WILMETTE HARBOR IL TO MICHIGAN CITY IN 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM WHITEHALL TO PENTWATER MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM GRAND HAVEN TO WHITEHALL MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM HOLLAND TO GRAND HAVEN MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM SOUTH HAVEN TO HOLLAND MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM ST. JOSEPH TO SOUTH HAVEN MI 5 NM OFFSHORE TO
MID LAKE-
421 AM CDT SUN JUL 24 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A CHANCE OF STORMS CAUSING WIND GUSTS IN EXCESS OF 35
KNOTS AND FREQUENT LIGHTNING. THE STRONGEST STORMS ARE LIKELY
OVER THE SOUTHERN PORTIONS OF THE LAKE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS WEDNESDAY THROUGH
FRIDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

KREIN

In the hours before

Local storm report, Jul 24, 12:46 AM CDT, 5 hours 58 minutes before

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Local storm report, Jul 24, 1:16 AM CDT, 5 hours 28 minutes before

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Special weather statement, Jul 24, 5:51 AM CDT, 53 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
551 AM CDT SUN JUL 24 2011

ILZ003-008-010-011-019-241115-
DE KALB IL-LA SALLE IL-LEE IL-OGLE IL-WINNEBAGO IL-
551 AM CDT SUN JUL 24 2011

...SPECIAL WEATHER STATEMENT...

AT 548 AM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED STRONG
THUNDERSTORMS ALONG A LINE EXTENDING FROM 21 MILES NORTHWEST OF
FORRESTON TO POLO TO 40 MILES SOUTHWEST OF WALTON...MOVING EAST AT 35
MPH.

WINDS UP TO 50 MPH...FREQUENT CLOUD TO GROUND LIGHTNING...HEAVY
DOWNPOURS...ARE POSSIBLE WITH THESE STORMS.

LOCATIONS IMPACTED INCLUDE...
  POLO...               FORRESTON...          DIXON...
  MOUNT MORRIS...       WALTON...             FRANKLIN GROVE...
  OREGON...             AMBOY...              ASHTON...
  PECATONICA...         LAKE SUMMERSET...     BYRON...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE
OBJECTS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS
TREES. HEAVY RAINFALL CAN LEAD TO FLOODING OF LOW LYING AREAS SUCH AS
DITCHES...VIADUCTS...UNDERPASSES...CREEKS AND DRAINAGE AREAS. SEEK
SHELTER IN A STURDY STRUCTURE UNTIL THESE STORMS HAVE PASSED.

LAT...LON 4221 8940 4249 8941 4249 8895 4160 8893
      4130 8898 4130 8917 4158 8918 4159 8964
      4192 8963 4193 8969 4220 8970

KREIN

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 23, 8:57 PM CDT	Areal Flood Advisory	LOT	Iroquois	4 hr
Jul 23, 9:18 PM CDT	Severe Thunderstorm Warning	LOT	Iroquois	57 min
Jul 23, 11:27 PM CDT	Special Weather Statement	LOT	Cook, DeKalb, DuPage, Kane	63 min
Jul 23, 11:43 PM CDT	Flash Flood Warning	LOT	Cook, DeKalb, DuPage, Grundy, Kane, Kendall and 2 more	6 hr
Jul 24, 5:51 AM CDT	Special Weather Statement	LOT	Lee, Ogle, Winnebago	24 min
Jul 24, 6:19 AM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Kane, Kendall, Lee, McHenry and 2 more	56 min
Jul 24, 8:16 AM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Kankakee, Livingston, Will	59 min
Jul 24, 8:26 AM CDT	Flash Flood Warning	LOT	Cook, Kane, Kendall, Will	106 min
Jul 24, 8:31 AM CDT	Special Weather Statement	LOT	DuPage	29 min
Jul 24, 8:54 AM CDT	River Flood Advisory	LOT	Kane, Kendall	11 hr
Jul 24, 10:07 AM CDT	Areal Flood Warning	LOT	Cook, Kane, Kendall, Will	6 hr
Jul 24, 9:19 AM CDT	Special Weather Statement	LOT	Benton, Jasper, Newton	41 min
Jul 24, 9:47 AM CDT	Special Weather Statement	LOT	Benton, Jasper	13 min
Jul 24, 5:43 PM CDT	Rip Current Statement	LOT	Lake, Porter	13 hr

Nearby

Severe Thunderstorm Warnings in Illinois, 2011 Every severe thunderstorm warning in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.