Strong to severe thunderstorms moved across many areas of northern Illinois during the afternoon and evening hours of May 11th.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LOT wrote it up.
Strong to severe thunderstorms moved across many areas of northern Illinois during the afternoon and evening hours of May 11th.
The local office's own words before the first event, 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 the first event at May 11, 2:02 PM CST, 37 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 302 PM CDT WED MAY 11 2011 .DISCUSSION... 249 PM CDT FOR THE REMAINDER OF THE AFTERNOON AND INTO THE EVENING...THE MAIN CONCERN WILL BE SEVERE THUNDERSTORM CHANCES...PARTICULARLY FOR LOCATION NORTH OF INTERSTATE 80 AND AWAY FROM LAKE MICHIGAN. EARLY THIS AFTERNOON...A LAKE BREEZE BOUNDARY HAS PUSHED INLAND...WEST OF LAKE COUNTY...AND AS OF 2PM CDT...THE BOUNDARY WAS APPROACHING A LINE FROM OHARE TO MIDWAY AIRPORTS. LOCATIONS EAST OF THE BOUNDARY WILL BE STABILIZED BY THE COOLER LAKE AIR...AND CONVECTIVE INITIATION WILL BE DIFFICULT TO SUPPORT. WEST OF THE BOUNDARY...THE ATMOSPHERE IS VERY WARM...MOIST AND UNSTABLE. SURFACE DEWPOINTS HAVE RISEN INTO THE UPPER 60S TO AROUND 70 AND TEMPERATURES ARE NEAR OR AT 90F. THE MAIN CONCERN FOR CONVECTIVE INITIATION HAS BEEN A WEAK CAPPING INVERSION OVER IL. LATEST ACARS SOUNDING INDICATE THAT THE CAP IS ERODING AND THAT CONVECTIVE INITIATION IS BECOMING MORE LIKELY THROUGH THE AFTERNOON. CAPE VALUES OVER NRN IL EXCEED 4000 J/KG WITH NO CIN. THUS A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR MUCH OF NRN IL WITH THE GREATEST THREATS BEING LARGE HAIL AND DAMAGING WIND. WHILE WIND PROFILES ARE NOT STRONGLY CONDUCIVE TO TORNADIC DEVELOPMENT...THE PRESENCE OF SFC BOUNDARY SUCH AS THE LAKE BREEZE PUSHING INLAND...THE POSSIBILITY OF ISOLATED TORNADIC DEVELOPMENT WILL NEED TO BE CONSIDERED. ANOTHER CONCERN WITH THE THUNDERSTORMS WILL BE THE FLASH FLOOD POTENTIAL. 12Z SOUNDINGS INDICATED PW AMOUNTS ON THE ORDER OF 1.5 INCHES AND WITH CONTINUED WARM/MOIST ADVECTION...PW VALUES SHOULD INCREASE THROUGH THE AFTERNOON...FURTHER ENHANCING THE POSSIBILITY OF LOCALLY HEAVY RAINFALL WITH THUNDERSTORMS. ALSO...IT IS EXPECTED THAT THE GREATEST SEVERE THREAT WILL LAST INTO THE EARLY EVENING HOURS...THERE IS A CHANCE THAT ISOLATED SUPERCELLS CAN CONSOLIDATE INTO A LINE OR BOX ECHO LATER THIS EVENING OVER THE WATCH AREA...WHICH COULD TRACK EWD INTO THE CHICAGO METRO AREA BY LATE EVENING. THUNDERSTORM POTENTIAL SHOULD DECREASE THROUGH THE LATE EVENING HOURS AND OVERNIGHT...THOUGH THERE WILL STILL BE A CHANCE FOR SHOWERS OR THUNDERSTORMS OVERNIGHT. AFTER ANOTHER DAY WITH TEMPERATURES AROUND 90F AND AMPLE LOW LEVEL MOISTURE IN PLACE...OVERNIGHT LOWS WILL BE ON THE BALMY SIDE...LIKELY ONLY DROPPING INTO THE MIDDLE TO UPPER 60S. AS THE DEEP UPPER LOW OVER THE CNTRL PLAINS IS EXPECTED TO BE SLOW TO PROGRESS EWD AS THE UPPER LEVEL PATTERN CONTINUES TO AMPLIFY...WARMER THAN NORMAL CONDITIONS WITH CHANCES FOR THUNDERSTORMS WILL CONTINUE UNTIL THE UPPER LOW CAN PROGRESS EAST OF THE REGION. THE MODELS ARE VERY CONSISTENT IN ACTUALLY DIGGING THE UPPER LOW SEWD...INTO SERN KS BY FRIDAY MORNING AND SRN IL BY FRIDAY NIGHT. A STRONG NRN STREAM SHORTWAVE IS ALSO EXPECTED TO DIG OUT OF SCNTRL CANADA AND INTO THE NRN PLAINS BY FRIDAY NIGHT. THIS WILL CARVE OUT A DEEP UPPER TROUGH OVER THE CNTRL CONUS. AS THE MEAN UPPER TROUGH MOVES OVER THE MIDWEST FRIDAY NIGHT AND INTO SATURDAY...CONDITIONS OVER THE LOCAL AREA WILL RAPIDLY DETERIORATE WILL TEMPERATURES SHARPLY DECREASING AND CHANCES FOR PRECIPITATIONS CONTINUING. THE WEEKEND IS SHAPING UP TO BE UNSEASONABLY COOL AND WET...WITH HIGHS ON SATURDAY RANGING FROM THE UPPER 50S TO AROUND 60F. HIGHS SUNDAY WILL LIKELY BE EVEN COOLER...GENERALLY IN THE LOWER TO MIDDLE 50S. UNSEASONABLY COOL WEATHER WILL CONTINUE INTO EARLY NEXT WEEK AS THE UPPER LOW DIGS INTO THE DEEP SOUTH. WITH THE GFS/ECMWF FAIRLY CONSISTENT ON THE GENERAL UPPER LEVEL FLOW PATTERN WITH TROUGHING REMAIN ALONG AND EAST OF THE MISSISSIPPI RIVER...THERE IS LITTLE OPPORTUNITY FOR ANY SIGNIFICANT WARMING UNTIL LATE NEXT WEEK. KREIN && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 20Z... * CHANCE FOR TSRA LATE THIS AFTERNOON INTO THE EVENING. * EAST TO SOUTHEAST WINDS CONTINUING. PAW //DISCUSSION...UPDATED 18Z... UPDATE 20Z...LAKE BREEZE PUSHED THROUGH ORD AND MDW AND NOW LOOKS LIKE WINDS WILL STAY EAST TO SOUTHEAST... FIRST CONCERN IS THE POTENTIAL FOR TSRA THIS AFTERNOON AND EVENING. MULTIPLE SURFACE BOUNDARIES OVER OR NEAR NORTHERN IL/NORTHWEST IN. UPPER LEVEL WAVE MOVING TOWARD THE AREA FROM THE SOUTHWEST. AMPLE LOW LEVEL MOISTURE IS IN PLACE. THE QUESTION IS WHETHER RELATIVELY WARM TEMPERATURES ALOFT WILL SERVE TO CAP ACTIVITY SIMILAR TO PAST COUPLE DAYS. MOST LIKELY TIME PERIOD FOR DEVELOPMENT WOULD BE ABOUT 21Z TO 02Z. CONFIDENCE IN OCCURRENCE TOO LOW AT THIS TIME TO INCLUDE IN THE TAFS AS A TEMPO GROUP. SECOND CONCERN IS THE WIND DIRECTION FOR NORTHEAST IL. HAVE HAD SOME LAKE INFLUENCE LATE MORNING. BUT WINDS BEHIND A BOUNDARY MOVING ACROSS NORTHERN IL EARLY THIS AFTERNOON WILL TURN WINDS MORE TO THE SOUTHWEST AGAIN AT THE TERMINALS. PAW //ORD AND MDW CONFIDENCE...UPDATED 20Z... * MEDIUM CONFIDENCE IN TSRA POTENTIAL. * MEDIUM CONFIDENCE IN WIND DIRECTION. PAW //OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z... THURSDAY NIGHT...VFR WITH CHANCE TSRA. FRIDAY...MVFR CIGS POSSIBLE WITH CHANCE OF TSRA EARLY. SATURDAY...MVFR CIGS POSSIBLE WITH CHANCE OF SHRA. SUNDAY...MVFR CIGS POSSIBLE WITH CHANCE OF SHRA. MONDAY...VFR. TUESDAY...VFR. MDB && .MARINE... 259 PM CDT WEAKENING LOW PRESSURE OVER WESTERN ONTARIO WILL TRACK TO THE EAST WHILE LOW PRESSURE CURRENTLY CENTERED OVER THE SOUTHERN PLAINS WILL TRACK NORTHEAST AND WEAKEN. THE TWO AREAS OF LOW PRESSURE WILL BE ABSORBED INTO A BROAD TROUGH OF LOW PRESSURE STRETCHING ACROSS THE GREAT LAKES REGION BY FRIDAY. THE TROUGH WILL GRADUALLY SHIFT SOUTH AND EAST...RECONSOLIDATING INTO A LOW CENTER BY SATURDAY OVER THE OHIO VALLEY. THIS LOW CENTER WILL GRADUALLY INTENSIFY AND TRACK NORTHEAST INTO THE EASTERN GREAT LAKES/INTERIOR NORTHEASTERN UNITED STATES BY EARLY NEXT WEEK. AFTER A PERIOD OF LIGHT WINDS AND RATHER VARIABLE WIND DIRECTIONS THROUGH EARLY FRIDAY...AS THE TROUGH OF LOW PRESSURE SETTLES TO THE EAST OF LAKE MICHIGAN BY LATER FRIDAY...WINDS WILL TURN NORTHERLY AND START TO INCREASE DUE TO A STRENGTHENING PRESSURE GRADIENT. OVER THE WEEKEND...WIND SPEEDS WILL CONTINUE TO GRADUALLY INCREASE ON THE BACKSIDE OF THE CONSOLIDATING LOW PRESSURE AREA...AND BECOME MORE NORTHEASTERLY. BY SUNDAY INTO MONDAY...NORTH AND NORTHEAST WINDS WILL LIKELY BE SUSTAINED TO 20 KNOTS...WITH HIGHER GUSTS TO 30 KNOTS POSSIBLE. A RIDGE OF HIGH PRESSURE WILL BUILD IN BY TUESDAY AND WEDNESDAY OF NEXT WEEK...BRINGING DIMINISHING WINDS. THERE WILL BE PERIODS OF SHOWERS AND THUNDERSTORMS AS LOW PRESSURE APPROACHES FROM THE PLAINS THROUGH EARLY FRIDAY. THE WARM AND HUMID AIR MASS IN PLACE OVER THE LAND AHEAD OF THE APPROACHING LOW IS SUPPORTIVE OF PATCHY DENSE FOG OVER THE OPEN WATERS DURING THE SAME TIME PERIOD. AFTER THE TROUGH PASSES TO THE EAST OF THE LAKE LATE FRIDAY...COOLER CONDITIONS OVER THE LAND WILL END THE FOG THREAT...WITH OCCASIONAL RAIN SHOWERS POSSIBLE OVER THE WEEKEND INTO THE BEGINNING OF NEXT WEEK. RC && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. &&
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
328 PM CDT WED MAY 11 2011
ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
122030-
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-
328 PM CDT WED MAY 11 2011 /428 PM EDT WED MAY 11 2011/
THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS...
NORTHEAST ILLINOIS AND NORTHWEST INDIANA.
.DAY ONE...TONIGHT.
WEATHER HAZARDS EXPECTED:
SCATTERED THUNDERSTORMS...SOME MAY PRODUCE:
LARGE HAIL UP TO THE SIZE OF HALF DOLLARS.
LOCALLY DAMAGING WINDS IN EXCESS OF 60 MPH.
HEAVY RAIN AND FREQUENT LIGHTNING.
AREAS AFFECTED AND TIMING:
SEVERE THUNDERSTORM CHANCES WILL PERSIST INTO THE EARLY
EVENING HOURS. THERE IS A CHANCE FOR NON-SEVERE
THUNDERSTORMS OVERNIGHT.
DISCUSSION:
AN UPPER LEVEL LOW OVER THE CENTRAL PLAINS CONTINUES TO HELP PUMP
HEAT AND HUMIDITY INTO THE MIDWEST. THIS HAS RESULTED IN SCATTERED
THUNDERSTORMS DEVELOPING THIS AFTERNOON OVER NORTH CENTRAL AND
NORTHEASTERN ILLINOIS. THE POTENTIAL FOR STRONG TO SEVERE
THUNDERSTORMS WILL CONTINUE INTO THE EVENING. THESE STORMS ARE
FUELED BY THE UNSEASONABLY WARM AND MOIST AIRMASS...WHICH WHEN
COMBINED WITH A JET STREAM ALOFT...MAY CAUSE SOME OF THE STORMS TO
BECOME SEVERE. THE MOST LIKELY HAZARD WILL BE LARGE HAIL AND
LOCALLY DAMAGING WINDS. THE POSSIBILITY OF ISOLATED TORNADOES
CANNOT BE RULED OUT AS WELL. THUNDERSTORMS WILL LIKELY DECREASE IN
COVERAGE AND INTENSITY BY LATE THIS EVENING.
IN ADDITION...PORTIONS OF THE KANKAKEE RIVER IN NORTHWEST INDIANA
WILL REMAIN IN FLOOD.
.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
THERE IS A CHANCE OF THUNDERSTORMS FROM THURSDAY MORNING THROUGH
FRIDAY AFTERNOON.
IN ADDITION...PORTIONS OF THE KANKAKEE RIVER IN NORTHWEST INDIANA
WILL REMAIN IN FLOOD.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL LIKELY BE NECESSARY THROUGH THIS EVENING.
&&
COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO
LMZ740>745-122030-
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-
328 PM CDT WED MAY 11 2011
THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE
WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE
MICHIGAN.
.DAY ONE...TONIGHT.
SCATTERED THUNDERSTORMS ARE POSSIBLE THIS EVENING.
THERE IS A CHANCE OF DENSE FOG TONIGHT...PARTICULARLY OVER THE
ILLINOIS NEARSHORE WATERS.
.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
THERE IS A CHANCE OF THUNDERSTORMS THURSDAY THROUGH EARLY FRIDAY
MORNING.
&&
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-
870-872-874-876-878-122030-
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-
328 PM CDT WED MAY 11 2011
THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE
MICHIGAN.
.DAY ONE...TONIGHT.
THERE IS A CHANCE OF THUNDERSTORMS OVER LAKE MICHIGAN TONIGHT.
IN ADDITION...AREAS OF DENSE FOG ARE EXPECTED TONIGHT.
.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
THERE IS A CHANCE OF THUNDERSTORMS THURSDAY INTO THURSDAY NIGHT.
ALSO...DENSE FOG IS POSSIBLE THURSDAY AND THURSDAY NIGHT.
&&
COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO
KREINThe Milwaukee radar (KMKX), 58 km away, was scanning. The volume nearest the first event began at 20:39 UTC.
14 hail, 7 thunderstorm wind, 4 flood. Local standard time, as filed.
Estimated wind gusts of 55 to 60 mph occurred on Okeson Road approximately one half a mile west of Greenwood Road.
Heavy rain caused 8 to 12 inches of standing water over Route 12 near Route 173.
Quarter size hail was reported at the intersection of Route 173 and Wilmot Road.
Quarter size hail was reported at the intersection of Plank Road and Route 20.
Walnut size hail was reported at the intersection of Main Street and Route 14 causing damage to cars.
Hail up to nickel size was reported across Lake in the Hills, including nickel size hail at the intersection of Randall Road and Algonquin Road, and dime size hail at the intersection of Randall Road and Ackman Road.
The intersection of Main Street and Berkshire Road was flooded after heavy rains fell across the area. A spotter in Lake in the Hills reported 2.45 inches fell in 90 minutes.
Quarter size hail was reported at Route 120 and Route 31.
Four inches of water was reported on Route 47, approximately a quarter mile north of Plato Center.
The intersection of Dundee Road and Golfview Lane was flooded. Two inches of rain fell over the hour leading up to this report.
Dime to nickel size hail was reported at the intersection of Route 14 and Route 47.
Nickel to quarter size hail was reported at Interstate 39 and Route 251.
Penny size hail was reported at the intersection of Waukegan Road and Shermer Road.
Eight power poles were blown down at Ashton Road and Interstate 80.
A tree fell blocking the road at Route 47 and Gardner Road.
Several trees were reported down at the Little Red School House.
Wind gusts were estimated to 60 mph.
Several reports of hail up to the size of quarters were received from the southern Chicago metro area. These reports include penny size hail in Hometown and quarter size hail reports in Evergreen Park and at the Interstate 94 and West 95th Street intersection.
Several trees were reported down near West 65th Street and South Oakley Avenue.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2011Every state in 2011This day in weather historyWarnings in Illinois, May 2011
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 300790, 300791, 300792, 300793, 300795, 300799, 300800, 300802, 300806, 300825, 300832, 300834, 307214, 307216, 300836, 300837, 300843, 300849, 300878, 300881, 300884, 300911, 300892, 300895, 300908.