Flash Flood and Flooding in Illinois, March 21 to 22, 2007

Name: Flash Flood and Flooding in Illinois, March 21 to 22, 2007
Start: 2007-03-21T15:06
End: 2007-03-22T12:00
Location: Illinois

March 21 to 22, 2007 · NWS LOT · 10 events in 6 counties and zones

Scattered thunderstorms developed during the late afternoon and evening hours of March 21st. Some of the thunderstorms briefly produced severe hail.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $50,000
Crop damage: None recorded
Events: 10

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.

What happened

The episode as NWS LOT wrote it up.

Scattered thunderstorms developed during the late afternoon and evening hours of March 21st. Some of the thunderstorms briefly produced severe hail.

What forecasters said that day

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 Mar 21, 2:15 PM CST, 51 minutes earlier.

Area forecast discussion, Mar 21, 2:15 PM CST, 51 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
315 PM CDT WED MAR 21 2007

.DISCUSSION FOR AFTERNOON ZONES/GRIDS...
315 PM CDT

SFC ANALYSIS AT 19Z INDICATED LOW PRES CENTERED OVR KS/NE WITH WARM
FRONT EXTENDING EWD ACROSS IOWA AND NRN IL. QUITE A DRAMATIC TEMP
DIFFERENCE ACROSS OUR CWA THIS AFTN AS IN THE WARM SECTOR (S OF
I-80) TEMPS HAVE CLIMBED WELL INTO THE 70S. ADDITIONAL CLOUD COVER
TO THE NORTH HAS LIMITED INSOLATION AND KEPT EXTREME NRN IL IN THE
60S. DEWPTS WERE GENERALLY IN THE UPR 50S ACROSS THE AREA.
INSTABILITY AND SHEAR ARE BOTH MARGINAL FOR SEVERE WITH CAPE AROUND
500 J/KG AND DEEP LAYER SHEAR APPROACHING 30KTS. ONE ROUND OF STORMS
CROSSING NWRN IL ATTM...SHOULD CLIP THE REGION NW OF A MENDOTA TO
WAUKEGAN LINE THROUGH EARLY EVENING. ANTICIPATE A SUBSEQUENT LULL
THIS EVENING...BEFORE NEXT ROUND OF STORMS ARRIVES LATE TONIGHT
ACCOMPANYING THE COLD FRONT WHICH IS HEADED THIS WAY FROM THE
DAKOTAS. MODELS POINTING AT STRONG DIFFLUENCE AT H2 AND SIGNIFICANT
H5 SHORTWAVE ENERGY ACCOMPANYING THE FROPA. WITH VERY MOIST AIR OUT
AHEAD OF THIS BOUNDARY....POTENTIAL FOR HEAVY RAIN EXISTS THROUGH
THE NIGHT. STRONG WIND FIELDS WILL KEEP STORM MOTION FAIRLY BRISK
AND WITH LATE EVENING BREAK IN THE ACTION...THIS SHOULD PREVENT MUCH
AREAL FLOOD CONCERN...THOUGH RIVERS WILL EXPERIENCE SOME RISES
IN RESPONSE TO THIS PRECIP.

FROPA WILL BE DELAYED TIL THURSDAY AFTN SOUTH OF I-80. WEAK HIGH
TRIES TO BUILD IN THURS NT. PRECIP WILL NOT BE FAR TO THE S
THOUGH...WITH BOUNDARY LINGERING ACROSS CENTRAL IL/INDY. NRN AND SRN
STREAMS OF H2 JET EVENTUALLY SYNC UP ACROSS IL/WI BY SAT AS SFC
BOUNDARY LIFTS NWD INTO NRN IL. THIS WILL LEAD TO A WET WEEKEND
ACROSS THE LOCAL AREA. DETAILS IMPOSSIBLE TO DISCERN THIS FAR OUT
WITH SUCH A COMPLICATED (BUT OBVIOUSLY WET) SITUATION...BUT WITH
LONGWAVE TROUGH IN THE WRN CONUS AND RIDGE AXIS TO OUR EAST...WELL
SEE RECURRING MID AND UPR TROPOSPHERIC SHORTWAVE TROUGHS RIPPLING
THROUGH THE AREA THROUGH EARLY TUESDAY...WITH COLD FRONT USHERING IN
DRIER AIR BEYOND THAT AS PER THE GFS MODEL. ECMWF IS SLIGHTLY SLOWER
WITH THAT FROPA AND WOULD KEEP PRECIP AROUND THROUGH TUES. NEXT
MAJOR SYSTEM SHOWN BY GLOBAL MODELS TO DEVELOP OVR THE NRN PLAINS BY
WED...BRINGING MORE PRECIP. TEMPS GENERALLY ABV NORMAL THROUGH THE
FCST PERIOD. WELCOME TO SPRING

RRH

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...SMALL CRAFT ADVISORY ILLINOIS NEARSHORE THROUGH 18Z THURS.
      SMALL CRAFT ADVISORY INDIANA NEARSHORE 18Z WED-18Z THURS.

&&

Hazardous weather outlook, Mar 21, 11:50 AM CST, 3 hours 16 minutes before

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1250 PM CDT WED MAR 21 2007

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-
019-220930-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
1250 PM CDT WED MAR 21 2007

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

.DAY ONE... THIS AFTERNOON AND TONIGHT

SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS THE REGION THROUGH
TONIGHT. A FEW STORMS COULD BE SEVERE LATE THIS AFTERNOON AND
EVENING...WITH THE PRIMARY RISK BEING LARGE HAIL...ESPECIALLY
NORTHWEST OF A LINE FROM PERU TO EVANSTON. LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE OVERNIGHT.

WATER LEVELS ON AREA RIVERS REMAIN HIGH...AND TOTAL RAINFALL AMOUNTS
THROUGH THURSDAY OF 1 TO 2 INCHES ARE EXPECTED. THIS ADDITIONAL
RAINFALL MAY RESULT IN RENEWED RISES ON MANY STREAMS IN THE AREA AND
A POTENTIAL FOR MINOR FLOODING.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

SHOWERS AND THUNDERSTORMS WILL BE CONTINUING EARLY THURSDAY MORNING.
BY MID MORNING THE SHOWERS AND THUNDERSTORMS ARE EXPECTED MAINLY
SOUTH OF INTERSTATE 80. SEVERE WEATHER IS NOT EXPECTED
THURSDAY...BUT LOCALLY HEAVY RAINFALL WILL REMAIN POSSIBLE.

HIGH WATER LEVELS ON AREA RIVERS COMBINED WITH THE NEW RAINFALL MAY
LEAD TO MINOR FLOODING PROBLEMS ON AREA STREAMS AND RIVERS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS AFTERNOON.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

LMZ740>745-766-220930-
WINTHROP HARBOR IL TO MICHIGAN CITY IN-
LAKE MICHIGAN-
1250 PM CDT WED MAR 21 2007

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

.DAY ONE... THIS AFTERNOON AND TONIGHT

A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE ILLINOIS NEARSHORE
WATERS THROUGH EARLY THURSDAY AFTERNOON. A SMALL CRAFT ADVISORY IS
IN EFFECT FOR THE INDIANA NEARSHORE WATERS FROM EARLY THIS AFTERNOON
THROUGH THURSDAY AFTERNOON.

SCATTERED THUNDERSTORMS ARE POSSIBLE ACROSS SOUTHERN LAKE MICHIGAN
FROM TODAY THROUGH THIS EVENING. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO INCREASE IN COVERAGE TOWARD THURSDAY MORNING AS A COLD
FRONT APPROACHES. WIND GUSTS IN EXCESS OF 35 KNOTS ARE POSSIBLE
TOWARD THURSDAY MORNING WITH THE THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR ALL OF THE
NEARSHORE WATERS THROUGH EARLY THURSDAY AFTERNOON.

SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS SOUTHERN LAKE MICHIGAN
THURSDAY MORNING. WIND GUSTS IN EXCESS OF 35 KNOTS ARE POSSIBLE
EARLY THURSDAY MORNING WITH THE THUNDERSTORMS.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

The radar

The Chicago radar (KLOT), 99 km away, was scanning. The volume nearest the first event began at 21:05 UTC.

Open the radar archive at this moment

Event by event

6 hail, 2 flood, 1 thunderstorm wind, 1 flash flood. Local standard time, as filed.

Hail, Lee

When: March 21, 3:06 PM CST to 3:08 PM CST
Where: Lee County, Ashton
Measured: 0.75 in hail
Reported by: Public
Coordinates: 41.870, -89.220

Flood, Lake

When: March 21, 3:15 PM CST to 6:15 PM CST
Where: Lake County, 1.02 mi W of Libertyville
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 42.280, -87.970

Eight to twelve inches of standing water reported on Route 176, 1/8 mile west of St. Mary's Road. Six inches of standing water on Bradley Road at Interstate 94.

Hail, Ogle

When: March 21, 3:27 PM CST to 3:30 PM CST
Where: Ogle County, Polo
Measured: 0.88 in hail
Reported by: Emergency Manager
Coordinates: 41.980, -89.580

Marble to Nickle size hail reported along Route 26 and US 52.

Hail, De Kalb

When: March 21, 3:47 PM CST to 3:50 PM CST
Where: De Kalb County, 1.03 mi W of Sycamore
Measured: 1 in hail
Reported by: Public
Coordinates: 41.980, -88.700

Flood, De Kalb

When: March 21, 3:55 PM CST to 6:55 PM CST
Where: De Kalb County, De Kalb
Cause: Heavy Rain
Reported by: Trained Spotter
Coordinates: 41.930, -88.750

Flooding reported on west side of NIU Campus, with water up to the bottom of car doors. One inch of rain reported in 30 minutes.

Hail, Cook

When: March 21, 4:02 PM CST to 4:05 PM CST
Where: Cook County, 0.51 mi E of Hanover Park
Measured: 0.88 in hail
Reported by: Public
Coordinates: 42.020, -88.170

Hail, Ogle

When: March 21, 4:11 PM CST to 4:13 PM CST
Where: Ogle County, 0.51 mi W of Byron
Measured: 0.75 in hail
Reported by: Broadcast Media
Coordinates: 42.130, -89.260

Thunderstorm Wind, McHenry

When: March 21, 5:09 PM CST
Where: McHenry County, 3.29 mi NE of Silver Lakes
Measured: 52 kt (60 mph) estimated gust
Reported by: Trained Spotter
Coordinates: 42.280, -88.200

Winds were estimated to 60 mph near Route 176 and River Road.

Hail, Lake

When: March 21, 6:09 PM CST to 6:12 PM CST
Where: Lake County, 0.69 mi N of Forest Lake
Measured: 0.88 in hail
Reported by: Amateur Radio
Coordinates: 42.280, -87.850

Flash Flood, Lake

When: March 21, 6:30 PM CST to March 22, 12:00 PM CST
Where: Lake County, Knollwood
Cause: Heavy Rain
Property damage: $50,000
Reported by: Broadcast Media
Coordinates: 42.280, -87.880

Three cars were submerged in flood waters up to eight feet deep on U.S. 41 between and Route 176 and 137. Mundelein reported 1.81 inches of rainfall.

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Illinois in 2007 Every state in 2007 This day in weather history Warnings in Illinois, March 2007

Sources

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: 21005, 21003, 21006, 21007, 21004, 21009, 21010, 21013, 21012, 22151.