Hail and Damaging Winds in Iowa, July 18, 2002

Name: Hail and Damaging Winds in Iowa, July 18, 2002
Start: 2002-07-18T21:45
End: 2002-07-18T21:50
Location: Iowa

July 18, 2002 · NWS ARX · 4 events in 1 county or zone

Straight-line winds estimated at 65 to 70 mph caused a farm shed to collapse, knocked down power poles and trees, as well as caused widespread damage to crops.

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: $13,000
Crop damage: $45,000
Events: 4

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 ARX wrote it up.

Straight-line winds estimated at 65 to 70 mph caused a farm shed to collapse, knocked down power poles and trees, as well as caused widespread damage to crops.

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 La Crosse, WI wrote its last area forecast discussion before the first event at Jul 18, 2:18 PM CST, 7 hours 27 minutes earlier.

Area forecast discussion, Jul 18, 2:18 PM CST, 7 hours 27 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
318 PM CDT THU JUL 18 2002

FORECAST CONCERNS THIS PACKAGE...SHRA/TSRA CHANCES TONIGHT/FRI...
SAT NIGHT INTO MON...AGAIN WED...TEMPS THRU THE PERIOD.

19Z DATA ANALYSIS SHOWED THE FRONTAL BOUNDARY BISECTING THE FORECAST
EAST-WEST. DEWPTS AROUND 70 TO LOWER 70S ALONG/SOUTH OF THE
BOUNDARY...WITH LAPS SOUNDINGS INDICATING CAPES ON THE ORDER OF 3000+
J/KG. WV AND KMPX WSR-88D LOOPS SHOWED A SHORTWAVE DROPPING SOUTHEAST
ACROSS CENTRAL MN. BLUE RIVER WI PROFILER SHOWS LITTLE IN THE WAY OF
SHEAR ALOFT...WHILE WOOD LAKE MN PROFILER ON THE SOUTHWEST SIDE OF
THE RATHER COMPACT SHORTWAVE SHOWS SHEAR ALOFT OF ABOUT 35 KTS. COMBO
OF EXTREME INSTABILITY...WEAK CONVERGENCE ALONG THE FRONT AND THE
SHORTWAVE TRIGGERING/MAINTAINING SHRA/TSRA ALONG THE BOUNDARY FROM
SOUTHEAST MN INTO EASTERN WI. INCREASING SHEAR WITH THE SHORTWAVE
HELPING TO INTENSIFY TSRA OVER SOUTHEAST MN EARLY THIS AFTERNOON.
ENTIRE COMPLEX OF SHRA/TSRA WAS MOVING SLOWLY TO THE SOUTHEAST.

NO MAJOR INITIALIZATION ERRORS NOTED WITH 12Z MODEL RUNS THIS
MORNING...AND ALL OFFER QUITE SIMILAR SOLUTIONS TO EACH OTHER AND
THEIR PREVIOUS RUNS THRU 48-60HRS. DIFFICULT TO FAVOR ONE MODEL
OVER THE OTHER AS ALL HAVE A REASONABLE DEPICTIONS OF SURFACE AND
SHRA/TSRA PLACEMENT ACROSS THE UPPER MIDWEST EARLY THIS AFTERNOON.
PER WV IMAGERY...ETA DOES LOOK TO HAVE THE EDGE WITH DEPICTION OF
THE SHORTWAVE OVER MN AND THE SHORTWAVE NEAR THE WESTERN SD/ND
BORDER. MINOR DIFFERENCES AMONG MODELS AGAIN LOOK TO HAVE LITTLE
IMPACT ON SENSIBLE WEATHER FOR THE AREA TONIGHT INTO SAT NIGHT.

IN THE SHORT TERM...ONGOING SHRA/TSRA WILL CONTINUE TO DEVELOP/
PROPAGATE SOUTHEAST ACROSS THE FORECAST AREA TONIGHT. LIKELY/
CATEGORICAL POPS CONTINUED MOST AREAS. MN SHORTWAVE AND UPPER TROUGH
OVER THE MID MS VALLEY CONTINUE TO DROP SOUTHEAST TONIGHT AND CARVE
OUT A BROAD TROUGH OVER THE EASTERN U.S. INTO THE WEEKEND. SD/ND
SHORTWAVE DROPS EAST/SOUTHEAST AS WELL TONIGHT/FRI. THIS 2ND WAVE
MAINTAINS LOW PRESSURE IN THE CENTRAL PLAINS...WHICH IN TURN HOLDS UP
THE FRONT ACROSS CENTRAL IA INTO FRI MORNING. PROXIMITY OF FRONT...
THE ABUNDANT LOW LEVEL MOISTURE...WEAK LOW LEVEL CONVERGENCE AND
FORCING FROM THE SHORTWAVE...WILL CREATE A CONTINUING CHANCE OF
SHRA/TSRA OVER MAINLY THE SOUTHWEST HALF OF THE FORECAST AREA ON
FRI...AND MAINLY IN THE MORNING. SOME DRIER AIR PUSHES EAST TO WEST
INTO THE AREA LATER FRI INTO SAT AS WEAK HIGH PRESSURE RIDGING AT
THE SURFACE AND ALOFT BUILDS SOUTH OVER THE GREAT LKS.

NEXT STRONGER SHORTWAVE TRACKS ACROSS SOUTHERN CANADA SAT/SUN...
FLATTENING THE UPPER RIDGE. SFC TROUGH STRENGTHENS INTO THE CENTRAL/
NORTHERN PLAINS BY 00Z SUN. OLD FRONTAL BOUNDARY WILL BE THE FOCUS
FOR MOISTURE POOLING/CONVERGENCE OVER SOUTHWEST IA/EASTERN NEB ON
SAT...WHICH LIFTS TOWARD THE AREA SAT NIGHT/SUN. BEST MOISTURE
TRANSPORT AND LOW/MID LEVEL Q-G CONVERGENCE REMAIN WELL WEST OF THE
AREA SAT. MEDIUM RANGE MODELS RATHER CONSISTENT THE PAST 2 TO 3 RUNS
WITH BRINGING THE LOW LEVEL TROUGH/COLD FRONT THRU THE AREA ON SUN...
WITH CHANCES SHRA/TSRA LINGERING SUN NIGHT INTO EARLY MON AS IT
PASSES. CANADIAN HIGH WITH SOME COOLER/DRIER AIR STILL SLATED TO
BUILD IN FOR LATER MON INTO EARLY WED. LATEST AVN/ECMWF/MRF ACTUALLY
SHOW MORE CONSISTENCY WITH EACH OTHER IN THE DAY 5-7 TIME-FRAME THAN
THEIR WED RUNS. 12Z AVN THIS MORNING TRENDS TOWARD 17/12Z ECMWF WITH
A SERIES OF WEAKER SHORTWAVES CARVING OUT BROAD TROUGH OVER CENTRAL
N.A. FOR THE MIDDLE OF NEXT WEEK. SERIES OF SHORTWAVES WILL PUSH
ANOTHER SURFACE TROUGH/FRONT AND CHANCE TSRA ACROSS THE AREA WED/WED
NIGHT.

NUMERICAL GUIDANCE LOWS SIMILAR FOR TONIGHT AND FRI NIGHT AND LOOK
REASONABLE. TRENDED TOWARD COOLER ETA AND AVN-MOS HIGHS FOR FRI WITH
SOME CLOUD COVER EXPECTED TO HOLD BACK HIGHS. GUIDANCE HIGHS QUITE
SIMILAR ON SAT AND LOOK GOOD...EXCEPT NGM-MOS HIGH AT KLSE. TRENDED
TOWARD ETA-MOS POPS THRU THE PERIOD.

.LSE...NONE.

RRS

In the hours before

Local storm report, Jul 18, 4:22 PM CST, 5 hours 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
522 PM CDT THU JUL 18 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0143 PM    1 W BYRON                 MN   .75 INCH HAIL
07/18/02   OLMSTED                        REPORTED BY BYRON FIRE
                                          DEPARTMENT

THOMPSON

The radar

The La Crosse radar (KARX), 147 km away, was scanning. The volume nearest the first event began at 03:43 UTC.

Open the radar archive at this moment

Event by event

3 thunderstorm wind, 1 hail. Local standard time, as filed.

Hail, Mitchell

When: July 18, 9:45 PM CST
Where: Mitchell County, Mitchell
Measured: 2 in hail
Property damage: $3,000
Crop damage: $8,000
Reported by: EMERGENCY MANAGER
Coordinates: 43.317, -92.883

Thunderstorm Wind, Mitchell

When: July 18, 9:45 PM CST
Where: Mitchell County, 2 mi SE of St Ansgar
Measured: 61 kt (70 mph)
Property damage: $4,000
Crop damage: $15,000
Reported by: NWS STORM SURVEY
Coordinates: 43.367, -92.900

Thunderstorm Wind, Mitchell

When: July 18, 9:50 PM CST
Where: Mitchell County, 1 mi W of Osage
Measured: 61 kt (70 mph)
Property damage: $5,000
Crop damage: $12,000
Reported by: NWS STORM SURVEY
Coordinates: 43.283, -92.833

Thunderstorm Wind, Mitchell

When: July 18, 9:50 PM CST
Where: Mitchell County, Mitchell
Measured: 55 kt (63 mph)
Property damage: $2,000
Crop damage: $10,000
Reported by: NWS STORM SURVEY
Coordinates: 43.317, -92.883

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.

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

The same day elsewhere

Every storm in Iowa in 2002 Every state in 2002 This day in weather history Warnings in Iowa, July 2002

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: 5308960, 5308961, 5308962, 5308963.