During the evening on July 4th, a line of thunderstorms moved across portions of the Upper Mississippi River Valley producing localized wind damage in Chickasaw County. These storms also disrupted numerous Independence Day festivities across the area.
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 evening on July 4th, a line of thunderstorms moved across portions of the Upper Mississippi River Valley producing localized wind damage in Chickasaw County. These storms also disrupted numerous Independence Day festivities across the area.
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 4, 5:46 PM CST, 9 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service La Crosse WI 646 PM CDT Thu Jul 4 2024 .KEY MESSAGES... - Moderate to High Confidence for Strong to Severe Storms Later This Afternoon & Early Evening. - Scattered to Isolated Pop-Up Shower & Storm Chances Friday & Saturday. - More Widespread Storm Chances For Sunday, Returning Monday Night and Tuesday Night. && .DISCUSSION... Issued at 1223 PM CDT Thu Jul 4 2024 Ongoing Storms & Precipitation This Morning & Afternoon: Have been monitoring multiple rounds of storms through this morning into the early afternoon with a quasi-closed upper-mid level area of lower heights in the Northern Plains and multiple surface frontal boundaries draped across the Upper Midwest. This area of lower heights is also embedded in a negatively tilted, amplified upper level longwave trough on GOES water vapor imagery early this afternoon. As a result, return flow has been advecting a more moist, more unstable airmass through the Plains into the Upper Mississippi River Valley. Initial, original synoptic forcing lifted through the Upper Mississippi River Valley early this morning, leaving an occluded surface low early this morning, placing the triple point to our west. Further occlusion and closing of the tightened warm sector has been firing off storms through western Minnesota early this afternoon. In the wake of morning precipitation, clearing skies seen on visible satellite imagery and are helping to build diurnal instability. Subsequent Forcing This Afternoon-Evening: With a formation of a subsequent low along the triple point with better synoptic forcing, quick-hitting deepening is expected, causing subsequent storm and precipitation chances later this afternoon and evening. The low is expected to trudge east-southeastward along the baroclinic boundary from west to east from central Minnesota into central Wisconsin, bringing the once stationary cold/dry surface frontal boundary with it. The passage of this frontal boundary will provide sufficient forcing for strong to severe storms. Timing of peak diurnal heating will be primary influence for location of highest impacts. Strong To Severe Storms This Evening: Confidence for strong to severe storms is moderate to high as the low center impacts the local area and the cold/dry surface frontal boundary provides sufficient subsequent forcing to conditionally unstable, nearly straight 7.0C/km soundings in upstream 04.12Z RAOBs. Overcoming any low level PBL inversion has been observed within the upstream clearing skies, shifting northeast early this afternoon through northern Iowa and southern Minnesota. Sufficient multi level speed and directional shear expected to sustain storms through the evening hours. High resolution forecast model soundings and associated hodographs suggest the potential for an initially discrete storm mode, albeit transiently, quickly congealing cold pools eventually making things messy before the mode becomes linear along the frontal boundary as 850-300 mean wind is weak, 10 to 20 kts. Taking the expected cold/dry frontal boundary motion into consideration, storm motion would be 20 to 30 kts to the east. Expected & Possible Hazards Into The Evening: All in all, primary hazard of large hail with strong to damaging winds possible. A quick spin up tornado cannot be ruled out where the low level shear vector best aligns (normal to line). Limiting factor will be initial storms potentially consuming initial low level instability. Shower & Storm Chances Friday: As the low shifts east of the local forecast area, wrap around cold air advection and tightened surface pressure gradient will result in perpetual shower and storm chances through Friday. Increased steepening of low level lapse rates concurrent with peak diurnal heating will allow parcels to tap into a long, skinny SBCAPE profile. The combination of transient saturation and little to no shear will result any storms quickly popping up and down. Could see some very limited opportunity for small hail given the cooler sounding but no shear quickly terminates any updraft sustenance, limiting overall chances and extent. Shower & Storm Chances This Weekend: The active pattern is expected to continue through the weekend. Upper level heights are never able to build, persisting synoptic troughing, perturbations, and precipitation chances. Saturday storm chances seem similar to Friday with waves of low level cold air advection within the upper level cold tongue, wobbles in the upper level low, and peak diurnal heating will cause scattered showers and isolated storms. A spatially limiting factor will be a narrow tongue of increased temperatures, increasing low level lapse rates and weakening any incoming storms. Through Start Of The New Week: Slightly different story for Sunday as diurnal heating advects a more moist airmass farther north into the Northern Plains. In turn, a widespread area of diurnally building instability affects much of Minnesota with long term global ensemble certainty for 500-1000 J/kg of SBCAPE taking shape. Have continued with National Blend which has Likely chances, for Sunday Night, Monday Night, and Tuesday Night. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 646 PM CDT Thu Jul 4 2024 Main taf concerns are storm chances early in the taf period...then ceilings lower to IFR/MVFR after 06z Friday. Latest mosaic radar shows convection over western Wisconsin into northeast Iowa and tracking east. This will impact LSE taf site for the next couple of hours this evening. Surface low spins over the region and ceilings lower to MVFR/IFR at both taf sites after 06z Friday. The lower ceilings linger into the daytime Friday. Question is how long MVFR/IFR conditions last at both taf sites during the day Friday. For now have introduced ceilings improving after 18z Friday. A few showers could rotate around the surface low into both the taf sites Friday. MVFR conditions underneath any of the showers should be brief and left mention out of both of the taf sites. && .HYDROLOGY... Issued at 400 AM CDT Wed Jul 3 2024 We continue to monitor river trends with the recent heavy rains with most rivers continuing to fall, however flood warnings continue for the Mississippi River and the Kickapoo at Viola. General rains of .5 to 1.5" are forecast with the greater confidence along and north of I90. Some spots per the 04.00Z HREF could see 2"+ with a 20-40% chance for Winona/Trempealeau Co. 6-hr flash flood guidance is generally 2 to 3 inches for flash flooding. Cannot rule out localized flash flooding with the storms later today and tonight if storms repeat over the same area. Be weather aware with outdoor activities and if traveling, be aware of your surroundings. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && DISCUSSION...JAR AVIATION...DTJ HYDROLOGY...Zapotocny
Hazardous Weather Outlook National Weather Service La Crosse WI 522 AM CDT Thu Jul 4 2024 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-051430- 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- 522 AM CDT Thu Jul 4 2024 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Today and Tonight Scattered storms with a few strong to severe this afternoon into early evening hours. Large hail is the primary threat, however damaging winds and locally heavy rain could occur. Flooding will continue along some area rivers. Please see the latest flood statements for additional details. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Storm chances continue Friday into early next week. At this time, confidence in severe thunderstorms remains low. Flooding will continue along some area rivers. Please see the latest flood statements for additional details. .SPOTTER INFORMATION STATEMENT... Storm spotters may be needed this afternoon and early this evening for areas southwest of I94. Storm and rainfall reports would be appreciated. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Zapotocny
Special Weather Statement National Weather Service La Crosse WI 248 PM CDT Thu Jul 4 2024 IAZ008-009-018-019-MNZ079-086>088-094-095-WIZ032-042200- Mitchell-Howard-Floyd-Chickasaw-Wabasha-Dodge-Olmsted-Winona- Mower-Fillmore-Buffalo- Including the cities of Osage, Cresco, Charles City, New Hampton, Wabasha, Dodge Center, Rochester, Winona, Austin, Preston, and Alma 248 PM CDT Thu Jul 4 2024 ...Thunderstorms Moving In For Late Afternoon...Strong To Severe Risk... Clusters of thunderstorms across southern Minnesota and northcentral Iowa will track northeast for the rest of the afternoon hours, shifting across parts of southeast Minnesota and northeast Iowa through 5 pm. Some will be strong, potentially severe. Hail is the main concern but any storm will be capable of 30 to 35 mph wind gusts. Locally heavy rainfall will also occur, which could lead to urban street flooding. Those will outdoor plans this 4th of July holiday should be prepared to seek indoor shelter should storms near your location. Have multiple ways to receive warnings if some are issued. Rieck
Special Weather Statement
National Weather Service La Crosse WI
416 PM CDT Thu Jul 4 2024
MNZ079-042200-
Wabasha MN-
416 PM CDT Thu Jul 4 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHERN WABASHA COUNTY THROUGH
500 PM CDT...
At 416 PM CDT, Doppler radar was tracking a strong thunderstorm near
Goodhue, or 14 miles south of Red Wing, moving east at 40 mph.
HAZARD...Wind gusts up to 50 mph and pea 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 storm will remain over mainly rural areas of northern Wabasha
County, including the following locations... Dumfries, Oak Center,
Maple Springs, Gilbert Valley, Bear Valley, and Zumbro Falls.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4437 9255 4437 9243 4445 9243 4445 9224
4444 9221 4440 9206 4437 9200 4427 9255
TIME...MOT...LOC 2116Z 251DEG 36KT 4436 9264
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
RieckSpecial Weather Statement National Weather Service La Crosse WI 454 PM CDT Thu Jul 4 2024 MNZ079-087-088-095-096-WIZ029-032>034-041-042-050000- Wabasha-Olmsted-Winona-Fillmore-Houston-Clark-Buffalo-Trempealeau- Jackson-La Crosse-Monroe- Including the cities of Wabasha, Rochester, Winona, Preston, Caledonia, Neillsville, Alma, Arcadia, Whitehall, Black River Falls, La Crosse, Sparta, and Tomah 454 PM CDT Thu Jul 4 2024 ...Thunderstorms Tracking Across The Area Into Early Evening... Clusters of thunderstorms were moving east northeast across southeast Minnesota and will push into portions of western Wisconsin through 7 pm. The stronger storms will be capable of 40 to 45 mph winds and 1/2 inch hail. An isolated severe storm remains possible. Locally heavy rainfall will also occur, which could lead to urban street flooding. Those will outdoor plans this 4th of July holiday should be prepared to seek indoor shelter should storms near your location. Have multiple ways to receive warnings if some are issued. Rieck
Special Weather Statement National Weather Service La Crosse WI 520 PM CDT Thu Jul 4 2024 IAZ008-009-018-019-050030- Mitchell-Howard-Floyd-Chickasaw- Including the cities of Osage, Cresco, Charles City, and New Hampton 520 PM CDT Thu Jul 4 2024 ...Thunderstorms Moving In For The Early Evening Hours... A cluster of thunderstorms will push east across portions of northeast Iowa for the early evening hours. The stronger storms will be capable of 40 to 50 mph wind gusts and 1/2 inch hail. A severe storm is possible. Locally heavy rainfall will also occur, which could lead to urban street flooding. Those with outdoor plans this 4th of July holiday should be prepared to seek indoor shelter should storms near your location. Have multiple ways to receive warnings if some are issued. Rieck
The La Crosse radar (KARX), 126 km away, was scanning. The volume nearest the first event began at 23:54 UTC.
1 thunderstorm wind. Local standard time, as filed.
Emergency management reported numerous trees and limbs down in Fredericksburg. This damaged power lines and a few homes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2024Every state in 2024This day in weather historyWarnings in Iowa, July 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: 1199859.