During the late afternoon hours on September 21st, an outflow boundary helped develop a supercell thunderstorm in Fillmore County. Soon after it developed it dropped golf ball sized hail two miles east of Whalan.
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 ARX wrote it up.
During the late afternoon hours on September 21st, an outflow boundary helped develop a supercell thunderstorm in Fillmore County. Soon after it developed it dropped golf ball sized hail two miles east of Whalan.
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 Sep 21, 2:23 PM CST, 19 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service La Crosse WI 323 PM CDT Sat Sep 21 2024 .KEY MESSAGES... - Showers and storms into tonight, few could be strong to severe. Rain chances linger for parts of northeast IA/southern or west central WI into Sunday - Below normal temps into early next week. && .DISCUSSION... Issued at 315 PM CDT Sat Sep 21 2024 Overview: Water vapor satellite imagery, heights, and lightning show a trough over southern Canada with another area of closed 500mb low pressure approaching the Four Corners region with a ridge over the Southern Plains. Lightning was occurring with scattered convection over parts of central and eastern WI and along a cold front across MN as well as ahead of the storm system in the southwest U.S. With the warm front lifting north, we did have a few strong to severe storms move through parts of northeast Iowa and western WI. At 20Z...an outflow boundary was pushing through parts of southwest WI with the surface warm front between PDC and DBQ. The surface cold front had pushed to south central MN, however there were showers continuing west of this area. Rest of today through Sunday night: The Canadian trough will continue to swing through the Mississippi Valley through Sunday morning. The will drag a cold front through the forecast area. Meanwhile, the closed low over the Four Corners region will open up and shift eastward through the Central Plains. Moisture transport will continue through the evening hours across the forecast area with MUCAPE of 2000J/kg per the SPC Mesoscale page, however the SBCAPE is around 2500J/kg across northern Iowa. Scattered showers and thunderstorms will continue ahead of the cold front with strong to severe storms possible due to the CAPE and effective shear around 45kts. The convection and outflow boundary could temper the severe potential farther north, however the instability and downdraft CAPE of 1200J/kg or higher could lead to some strong to severe storms. The winds will veer with time, however the instability lingers into the evening. The CAMs were dry for the early day/early afternoon convection, thus not doing well with the pre-frontal storms. Hopefully, the RAP/HRRR has a handle on increasing convection through the afternoon with the showers/storms gradually pushing east through 07Z. The CAMs do hint at re-developing across the southern part of the forecast area for after 07Z into Sunday morning. Showers should gradually exit the area during the afternoon with cooler air for the area. Highs Sunday should top out in the mid 60s and lower 70s, more seasonable for this time of year. Monday through the week: Behind the weekend cold frontal system, cooler conditions look to continue for the start the week with highs in the upper 60s to low 70s and lows in the 40s to low 50s. Model guidance continues to suggest a shortwave trough in the northern flow while shortwave energy slides just south of the local area for the early part of the work week. There remain some differences between the individual GEFS/ECMWF ens solutions on precipitation potential. However, have noted a very slight trend towards a drier solution in the most recent blended model guidance, which currently keeps 15-20% chances in far southwest WI for late Monday night into Tuesday. Behind the upper level trough, guidance looks to favor upper level ridging building eastward. Still some variability, but GEFS/EPS ens solutions do not show a strong/definitive QPF signal through much of the rest of the week. Otherwise, temperatures are forecast to gradually increase back into the mid/upper 70s by the end of the week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1255 PM CDT Sat Sep 21 2024 A warm front is lifting into the area today followed by a cold front tonight. These weather systems will bring scattered showers and thunderstorms to the area. The hi-res CAMs are going to have to catch of with the showers developing with the warm front at the models were dry. Will continue to refine the timing of showers/storms until the drier and cooler air arrives. It appears the showers/storms exit RST by around 06 or 07Z and 09Z at KLSE, however re-development will be possible until the mid-level trough pushes through Sunday morning. South to southeast surface winds 5 to 15kts with some stronger gusts at KRST shift to the southwest and northwest with the frontal passage this afternoon and early this evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && DISCUSSION...EMS/Zapotocny AVIATION...Zapotocny
Hazardous Weather Outlook National Weather Service La Crosse WI 222 PM CDT Sat Sep 21 2024 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-221100- Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette- Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston- Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau- Adams-Vernon-Crawford-Richland-Grant- 222 PM CDT Sat Sep 21 2024 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Tonight Scattered thunderstorms with a lightning risk are expected into the evening hours. Stronger storms, primarily in northeast Iowa and western Wisconsin could occasionally bring hail and gusty winds. .DAYS TWO THROUGH SEVEN...Sunday through Friday A few non-severe storms remain possible Sunday, generally south of Interstate 90. .SPOTTER INFORMATION STATEMENT... While widespread spotter activation is not anticipated, observations of hail or gusty winds would be appreciated. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Rieck/Shea
Preliminary Local Storm Report
National Weather Service La Crosse WI
212 PM CDT Sat Sep 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0157 PM Hail 5 W Hillsboro 43.65N 90.43W
09/21/2024 E1.00 Inch Vernon WI Emergency Mngr
Reported by Hillsboro EM.
&&Preliminary Local Storm Report
National Weather Service La Crosse WI
214 PM CDT Sat Sep 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0201 PM Hail 3 NW Mather 44.17N 90.35W
09/21/2024 E0.25 Inch Jackson WI CO-OP Observer
Reported as slivers.
&&Preliminary Local Storm Report
National Weather Service La Crosse WI
228 PM CDT Sat Sep 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1237 PM Hail Holmen 43.97N 91.26W
09/21/2024 E0.50 Inch La Crosse WI Public
Time estimated.
&&Preliminary Local Storm Report...Summary
National Weather Service La Crosse WI
300 PM CDT Sat Sep 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1132 AM Hail Ferryville 43.35N 91.08W
09/21/2024 E0.25 Inch Crawford WI Public
Relayed via MPing.
1140 AM Hail 2 N Prairie Du Chien 43.07N 91.14W
09/21/2024 M0.25 Inch Crawford WI Public
1200 PM Hail Readstown 43.45N 90.76W
09/21/2024 M0.25 Inch Vernon WI Trained Spotter
1237 PM Hail Holmen 43.97N 91.26W
09/21/2024 E0.50 Inch La Crosse WI Public
Time estimated.
1237 PM Hail 2 NW Four Corners 44.10N 90.94W
09/21/2024 E1.00 Inch Monroe WI Public
Time estimated. Social Media report.
1240 PM Hail 4 W North Bend 44.09N 91.19W
09/21/2024 M1.25 Inch Trempealeau WI Public
0157 PM Hail 5 W Hillsboro 43.65N 90.43W
09/21/2024 E1.00 Inch Vernon WI Emergency Mngr
Reported by Hillsboro EM.
0201 PM Hail 3 NW Mather 44.17N 90.35W
09/21/2024 E0.25 Inch Jackson WI CO-OP Observer
Reported as slivers.
&&Preliminary Local Storm Report
National Weather Service La Crosse WI
305 PM CDT Sat Sep 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0257 PM Hail 4 S Colby 44.85N 90.32W
09/21/2024 M0.25 Inch Clark WI Public
Lasted approx 5 min.
&&Special Weather Statement
National Weather Service La Crosse WI
332 PM CDT Sat Sep 21 2024
WIZ017-212100-
Taylor WI-
332 PM CDT Sat Sep 21 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN TAYLOR COUNTY
THROUGH 400 PM CDT...
At 332 PM CDT, Doppler radar was tracking a strong thunderstorm near
Sheldon, or 15 miles southeast of Ladysmith, moving east at 20 mph.
HAZARD...Wind gusts of 50 to 55 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
This strong thunderstorm will be near...
Jump River around 340 PM CDT.
Other locations impacted by this storm include County Roads D And N.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4525 9051 4528 9092 4538 9092 4538 9050
TIME...MOT...LOC 2032Z 266DEG 19KT 4531 9087
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...55 MPH
FergusonThe La Crosse radar (KARX), 57 km away, was scanning. The volume nearest the first event began at 20:43 UTC.
2 hail. Local standard time, as filed.
Trained spotters reported golf ball sized hail 2 miles east of Whalan.
Emergency management reported nickel sized hail in Bratsberg.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2024Every state in 2024This day in weather historyWarnings in Minnesota, September 2024
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: 1213477, 1213478.