Tornadoes and Flash Flood in Wisconsin, July 24, 2009

Name: Tornadoes and Flash Flood in Wisconsin, July 24, 2009
Start: 2009-07-24T16:05
End: 2009-07-24T20:30
Location: Wisconsin

July 24, 2009 · NWS MKX · 8 events in 2 counties and zones

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. 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: $1.2 million
Crop damage: $13 million
Events: 8

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 MKX wrote it up.

A cold front crossed Wisconsin during the late afternoon and evening hours of July 24th. Large scale lift and deep layer wind shear associated with upper level low pressure moving into the region led to the development of supercell thunderstorms in southwest Wisconsin. Severe thunderstorm wind gusts, large hail, and two tornadoes were reported in Lafayette County with the supercell storms.

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 Milwaukee, WI wrote its last area forecast discussion before the first event at Jul 24, 2:15 PM CST, 1 hour 50 minutes earlier.

Area forecast discussion, Jul 24, 2:15 PM CST, 1 hour 50 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
315 PM CDT FRI JUL 24 2009

.SHORT TERM /TONIGHT THROUGH MONDAY/...
IMMEDIATE FOCUS LIES ON THUNDERSTORM THREAT FOR THE REMAINDER OF THE
AFTERNOON INTO THIS EVENING.  SCATTERED CONVECTION HAS DEVELOPED
JUST TO THE NORTH OF SEVERE THUNDERSTORM CURRENTLY JUST WEST OF
KDBQ.  THINKING CONVECTION IS A RESULT OF INCREASING MID LEVEL WARM
AIR ADVECTION AND THETA-E ADVECTION...WHICH SPREADS ACROSS SOUTH
CENTRAL WISCONSIN THROUGH EARLY EVENING.  MID LEVEL LAPSE RATES IN
THE TRI-STATE AREA HAVE INCREASED TO 7-7.5 DEGREES SO ATMOSPHERE
RECUPERATING RAPIDLY DESPITE RECENT CONVECTION.  MUCAPE IN THIS AREA
AROUND 1000 J/KG WITH SURGE OF MID 60 DEGREE DEWPOINTS.  BULK WIND
SHEAR HAS INCREASED TO 50 KTS IN THIS AREA AS WELL.  DESPITE JUST
BEING REMOVED FROM SPC SLIGHT RISK...COULD STILL SEE SOME LARGE HAIL
AND DAMAGING WIND INTO THIS EVENING WITH BEST POTENTIAL IN THE
WESTERN CWA AS DEPICTED BY LATEST WRF4G MESOMODEL.  PWAT VALUES
INCREASE TO AROUND 1.5 INCHES AHEAD OF APPROACHING SURFACE FRONT
WHICH MOVES THROUGH DURING THE EVENING.  SYNOPTICALLY...AREA OF
UPPER LEVEL DIVERGENCE ASSOCIATED WITH NOSE OF 300MB JET.  WIND
PROFILER NETWORK AND WATER VAPOR IMAGERY SHOW POTENT SHORT WAVE
TROUGH UPSTREAM OVER SRN MN...SO STILL THINKING SHOWERS AND
THUNDERSTORMS WILL BE LIKELY ACROSS CWA THIS EVENING...DIMINISHING
RAPIDLY FROM LATE EVENING THRU 09Z.

POTENT SHORT WAVE TROUGH ROTATES AROUND UPPER LOW SETTLING OVER
GREAT LAKES ON SATURDAY.  STEEP LAPSE RATES AND LINGERING LOW LEVEL
MOISTURE SHOULD PRODUCE AT LEAST SCATTERED SHOWERS.  WEAK ELEVATED
INSTABILITY SO WL CONTINUE TO MENTION ISO THUNDER.  SECONDARY WEAKER
SHORT WAVE ON SUNDAY ROTATES AROUND DEPARTING LOW SO WL CONTINUE
SMALL THREAT.  MORE POTENT SHORT WAVE TROUGH ROTATES THROUGH LATER
MONDAY AND MONDAY NIGHT.  SLIGHT DELAY IN TROUGH ARRIVAL...HOWEVER
LOW LEVEL WARM AIR ADVECTION SPREADS IN MONDAY MORNING SO WL
CONTINUE LOW POPS THROUGH MONDAY...WITH BETTER THREAT MONDAY
EVENING.

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
EXTENDED GUIDANCE IN REASONABLE AGREEMENT ON BRINGING COLD FRONT AND
STRONGER UPPER LEVEL SHORT WAVE ACROSS WISCONSIN IN THE MONDAY
AFTERNOON INTO TUESDAY TIME FRAME.  GFS LIKELY OVERDOING AMOUNT OF
LOW LEVEL MOISTURE AVAILABLE BUT BEST THREAT FOR MORE WIDESPREAD
CONVECTION AT THIS TIME...AFTER TONIGHT.  LATEST GFS AND HI RES
ECMWF SHOWING SOME FLATTENING OF PERSISTENT LONG WAVE TROFFING
ACROSS UPPER MIDWEST INTO SRN CANADA POST CDFNT NEXT TUE THROUGH
THU.  12Z GFS SHOWING STRONG SHORT WAVE AFFECTING SRN WI ON
WED...BUT MEDIUM RANGE ENSEMBLE POPS HAS POPS LESS THAN 20 PERCENT.
MORE STOCK PLACED IN MREF DUE TO FAIR TO GOOD AGREEMENT IN ENSEMBLE
MEMBERS.  HI RES AND CANADIAN IN AGREEMENT ON DRIER WEATHER FROM TUE
NIGHT INTO THU SO PER COORDINATION WITH NEIGHBORING OFFICES...HAVE
REMOVED POPS FOR MOST OF THIS PERIOD.

STRONGER SHORT WAVE TROUGH AMPLIFIES UPSTREAM TROFFING ACROSS NORTH
CENTRAL CONUS LATER NEXT WEEK WITH THREAT FOR CONVECTION RETURNING
BY THU NIGHT/FRIDAY.  TEMPERATURES THROUGH THE END OF THE WEEK LOOK
TO CONTINUE BELOW NORMAL FOR LATE JULY.

GFS 5 DAY 500MB ANOMALIES SHOW LITTLE CHANGE TO THE OVERALL PATTERN
INTO THE FIRST WEEK OF AUGUST...WITH LARGE POSITIVE ANOMOLY
PERSISTING ACROSS WRN CANADA INTO PAC NW...WITH DOWNSTREAM LONG WAVE
TROFFING ACROSS CENTRAL CANADA INTO GTLAKES.

&&

.AVIATION...STILL EXPECT A ROUND OF THUNDERSTORMS TO CROSS SOUTHERN
WISCONSIN THIS EVENING WITH APPROACHING LOW PRESSURE CENTER AND
ASSOCIATED FRONTAL BOUNDARIES. POTENTIAL FOR SEVERE WEATHER WITH
THESE STORMS.  OVERALL EXPECT VFR CONDITIONS BUT IFR CONDITIONS
POSSIBLE IN AND AROUND STRONGER THUNDERSTORMS. COLD FRONT EXPECTED
TO MOVE THROUGH BTWN 06Z AND 12Z WITH WINDS SHIFTING TO THE
NORTHWEST BEHIND THE FRONT. POSSIBLE THUNDERSTORM DEVELOPMENT ONCE
AGAIN TOMORROW AFTERNOON BUT LEFT OUT OF TAFS FOR NOW WITH ONLY
CHANCE POPS.

&&

.MARINE...GUSTY SOUTHWEST WINDS EXPECTED TONIGHT AHEAD OF COLD FRONT
MOVING THROUGH. THUNDERSTORM CHANCES ALSO INCREASE THIS EVENING WITH
SOME SEVERE THUNDERSTORMS POSSIBLE.  WINDS INCREASE OUT OF THE
NORTHWEST SATURDAY AFTERNOON BUT AT THIS TIME EXPECT TO REMAIN BELOW
SMALL CRAFT LEVELS.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

SHORT/LONG TERM...MBK
AVIATION/MARINE...PZ

Hazardous weather outlook, Jul 24, 2:30 PM CST, 1 hour 35 minutes before

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
330 PM CDT FRI JUL 24 2009

WIZ046-047-051-052-056>060-062>072-251030-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
330 PM CDT FRI JUL 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN.

.DAY ONE...TONIGHT

THUNDERSTORMS ARE EXPECTED THIS EVENING ACROSS SOUTHERN WISCONSIN.
ISOLATED SEVERE ACTIVITY IS POSSIBLE...ESPECIALLY SOUTHWEST OF A
WISCONSIN DELLS...TO MADISON...TO BELOIT LINE...HOWEVER MOST STORMS
SHOULD STAY BELOW SEVERE LIMITS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE EACH DAY FROM THE
WEEKEND INTO EARLY NEXT WEEK AS RELATIVELY COLD AIR WILL BE
PRESENT IN THE UPPER ATMOSPHERE MAKING FOR UNSTABLE CONDITIONS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION SHOULD NOT BE NEEDED TONIGHT.

LMZ643>646-251030-
SHEBOYGAN TO PORT WASHINGTON WI-
PORT WASHINGTON TO NORTH POINT LIGHT WI-
NORTH POINT LIGHT TO WIND POINT WI-
WIND POINT WI TO WINTHROP HARBOR IL-
330 PM CDT FRI JUL 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE EXPECTED THIS EVENING.  THESE STORMS
SHOULD STAY BELOW SEVERE LIMITS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE EACH DAY FROM THE
WEEKEND INTO THE EARLY NEXT WEEK AS RELATIVELY COLD AIR WILL BE
PRESENT IN THE UPPER ATMOSPHERE MAKING FOR UNSTABLE CONDITIONS.

WWW.WEATHER.GOV/MKX

ZABEL

The radar

The Quad Cities radar (KDVN), 123 km away, was scanning. The volume nearest the first event began at 22:07 UTC.

Open the radar archive at this moment

Event by event

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

Hail, Lafayette

When: July 24, 4:05 PM CST
Where: Lafayette County, 2 mi SW of Belmont to 6 mi SE of Shullsburg
Measured: 2.75 in hail
Property damage: $500,000
Crop damage: $6.4 million
Reported by: Law Enforcement
Coordinates: 42.709, -90.358

A 5-mile wide hail swath damaged crops (corn, soy beans, wheat, and alfalfa), vehicles (windows and dents), and at least 25 homes (windows, siding, and roofs). This hail swath merged with a another, later, hail swath, with the merger southeast of Shullsburg. Some fields southeast of Shullsburg were totally stripped by the hail stones.

Newspaper accounts indicated that the two hail swaths resulted in damage to 20,000 acres of corn and 10,000 acres of soybeans in Lafayette County. Using an avarge of 135 bushes of corn per acre with a price of $3.45 per bushels yields a corn loss of $9.315 M. Using an average of 38 bushels of soybeans per acre, and a price of $9.25 per bushel yields a soybean loss of $3.515 M. These loss estimates were divided by two and assigned to the two hail swaths equally.

Thunderstorm Wind, Lafayette

When: July 24, 4:05 PM CST to 4:10 PM CST
Where: Lafayette County, 4 mi W of Belmont to 5 mi SSW of Belmont
Measured: 78 kt (90 mph) estimated gust
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.730, -90.409

Powerful thunderstorm winds toppled dozens of trees and damaged a shed.

Tornado, Lafayette

When: July 24, 4:12 PM CST to 4:17 PM CST
Where: Lafayette County, 2.91 mi SSW of Seymour Corners to 2.16 mi NNE of Shullsburg
Rating: EF0
Path length: 3.36 mi
Path width: 75 yd
Property damage: $100,000
Crop damage: $10,000
Reported by: NWS Storm Survey
Coordinates: 42.630, -90.268

A weak tornado spun up a little north of the intersection of CTH Q and Prairie Rd. (about 4 miles northwest of Shullsburg). It proceded to move on a 145 degreee bearing southeast to just southeast of the intersecton of CTH U and Jackson Rd. a couple miles north-northeast of Shullsburg. Major damage was inflicted on a barn and storage pole shed, several trees were uprooted or snapped, and some minor damage was inflicted on a corn field. The specific starting and ending GPS coordinates were 42.63011/-90.26829 and 42.59963/-90.21671, and the damage intensity was based on DI 1 (SBO), DOD 8. The average width was about 30 yards. The wind was estimated to be about 105 mph.

Hail, Lafayette

When: July 24, 5:18 PM CST to 5:35 PM CST
Where: Lafayette County, 1 mi W of Benton to 6 mi SE of Shullsburg
Measured: 2.75 in hail
Property damage: $500,000
Crop damage: $6.4 million
Reported by: Law Enforcement
Coordinates: 42.570, -90.400

A 5-mile wide hail swath damaged crops (corn, soy beans, wheat, and alflafa), vehicles (dents and broken windows), and at least 25 homes (roofs, windows, and siding). This swath merged with another hail swath from an ealier storm that traveled from Northwest Lafayette County to southeast of Shullsburg. Some farm fiels were stripped to nothing by the hail stones.

Thunderstorm Wind, Lafayette

When: July 24, 5:18 PM CST to 5:35 PM CST
Where: Lafayette County, 2 mi SW of Benton to 6 mi SE of Shullsburg
Measured: 78 kt (90 mph) estimated gust
Reported by: Law Enforcement
Coordinates: 42.550, -90.408

Powerful thunderstorm winds toppled dozens of trees.

Tornado, Lafayette

When: July 24, 5:32 PM CST to 5:40 PM CST
Where: Lafayette County, 1.82 mi NNE of New Digging to 3.43 mi S of Shullsburg
Rating: EF0
Path length: 4.16 mi
Path width: 50 yd
Property damage: $50,000
Crop damage: $10,000
Reported by: NWS Storm Survey
Coordinates: 42.553, -90.312

A weak tornado spun up about 1/3 mile south-southwest of the intsection of STH 11 and CTH I, or roughly a couple northeast of New Diggings. It proceded to move on a 122 degreee bearing southeast to about 1/3 mile east of the intersecton of CTH O and Blackhawk Rd., about 3.5 miles southeast of Shullsburg. A small pole shed was destroyed and small portions of a side-wall and roof of a home were peeled off. Otherwise several trees were uprooted or snapped. The specific starting and ending GPS coordinates were 42.55270/-90.31193 and 42.52115/-90.24236, and the damage intensity was based on DI 1 (SBO), DOD 6. The average width was about 25 yards. The wind was estimated to be about 90 mph.

Flash Flood, Lafayette

When: July 24, 6:00 PM CST to 8:30 PM CST
Where: Lafayette County, 4 mi NW of New Digging to 3 mi WNW of New Digging
Cause: Heavy Rain
Property damage: $30,000
Reported by: Law Enforcement
Coordinates: 42.571, -90.386

Repeated heavy rains from a couple thunderstorms resulted in flash flooding in the area from New Diggings to southeast of Shullsburg. All rivers and streams in this area rose above flood stage, and many roads had water over them. Some roads had depths of 2 to 3 feet of fast-flowing water. Several of the gravel shoulders were washed out, and lots of vegetative debris was left on some roads.

High Wind, Rock

When: July 24, 6:45 PM CST to 7:15 PM CST
Where: Rock forecast zone
Measured: 50 kt (58 mph) estimated gust
Reported by: Law Enforcement
Coordinates: 42.671, -89.072 (the zone’s center; the record gives no point)

Many large trees in or near the city of Beloit were uprooted or damaged by powerful, non-thunderstorm, gradient high winds due to a wake-low situation. A thunderstorm complex had previously moved west to east across northern Illinois, while an area of low pressure developed over the Wiscosnin River Valley northwest of Madsion. The resultant increase in the surface pressure gradient across southern Wisconsin resulted in the development of high winds.

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
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.
Tornado: A violently rotating column of air in contact with the ground and extending from a thunderstorm, filed with its path, width and Fujita or Enhanced Fujita rating from the damage survey.
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.
High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.

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

The same day elsewhere

Every storm in Wisconsin in 2009 Every state in 2009 This day in weather history The tornado archive for Wisconsin, 2009 Warnings in Wisconsin, July 2009

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: 191609, 191615, 191642, 191612, 191617, 191644, 191650, 191652.