Following morning convection over central and southern Iowa tied to a system further south into Missouri, a frontal boundary sweeping across northern into the eastern parts of Iowa by the afternoon to evening resulted in additional showers and thunderstorms. The parameter space overhead included MLCAPE values of 1000+ J/kg and deep layer shear around 40-50+ knots.
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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 DMX wrote it up.
Following morning convection over central and southern Iowa tied to a system further south into Missouri, a frontal boundary sweeping across northern into the eastern parts of Iowa by the afternoon to evening resulted in additional showers and thunderstorms. The parameter space overhead included MLCAPE values of 1000+ J/kg and deep layer shear around 40-50+ knots. In particular, Cerro Gordo county received severe thunderstorm wind damage, with estimated gusts around 58 mph. Otherwise, no other reports were received for this particular event.
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 Des Moines, IA wrote its last area forecast discussion before the first event at Jul 4, 1:19 PM CST, 2 hours 21 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Des Moines IA 219 PM CDT Thu Jul 4 2024 .KEY MESSAGES... - Scattered thunderstorms north and northeast this afternoon and evening. Severe weather possible, primarily in the form of hail, along with locally heavy rainfall. - Relatively cool and cloudy on Friday with scattered light showers and isolated thunderstorms. - Steady temperatures from this weekend through the first half of next week, with periodic thunderstorm chances beginning around Saturday night. && .DISCUSSION... Issued at 218 PM CDT Thu Jul 4 2024 Well-anticipated thunderstorms are tracking across northern Iowa early this afternoon, within a region of enhanced instability ahead of an approaching cold front. Storm intensity has been held in check by a relative lack of low-level shear, but should slowly increase over the next few hours leading to a threat of severe weather primarily in the form of hail as the front and storms move eastward across the area. Once they clear out later this evening we will then see several hours of dry and quiet weather. However, the 500 mb low over Minnesota will drift slowly southeastward into Wisconsin by Friday morning, spreading a shield of clouds and light showers/isolated thunderstorms across parts of Iowa from later tonight in the north and expanding through the day Friday. Rain will be most likely across the northeastern half of the state, closer to the low, but there is enough signal further southwest that low POPs have been included for virtually the entire forecast area on Friday afternoon. The clouds will keep temperatures unseasonably low during the day, and have continued to nudge high temps down with low to mid 70s forecast across much of the area. This will also limit instability and severe weather is not expected with the isolated storms on Friday. From Friday night into Saturday weak ridging will briefly move across the area providing a respite, but by Saturday evening, as a broad mid-level trough begins to carve out over the north central U.S., the leading shortwave impulse within that trough will round the base near the South Dakota/Nebraska border and generate late day thunderstorms over Nebraska that will move eastward toward Iowa on Saturday night. Current indications are that decent flow aloft and broad forcing concurrent with the approaching mid-level shortwave could support some threat of strong to severe storms in our area, however, this is mitigated by only modest instability with such a short airmass recovery time behind the Friday coolness. Even so, with decent warming and moistening on Saturday afternoon, Saturday night will be a period to watch for potential severe weather. During the first half of next week, from Sunday through around Wednesday, the slowly deepening northern U.S. trough will dominate our region and prevent any significant warming, with daily highs generally in the upper 70s to mid 80s during that time. Subtle impulses moving through the trough will also provided opportunities for periodic showers and storms, however, the timing and placement of any such precipitation is highly uncertain at this range. There are now increasing signals that a large heat dome building over the southwestern U.S. by the middle of next week may finally expand eastward and push away the trough by the following weekend, supporting generally hotter and drier weather by that time. However, that is beyond the scope of the 7-day forecast so we will have to wait to see if it pans out over the next few days. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1214 PM CDT Thu Jul 4 2024 Scattered thunderstorms will affect the area through this evening, with MCW, FOD, and ALO the sites most likely to be impacted. Have included targeted TEMPO groups at those terminals between 19Z and 01Z, with only VC groups further south at DSM/OTM. Amendments are anticipated based on short-term storm trends. Once those clear the area after 00Z however, VFR conditions are expected for much of the night before low ceilings and light showers move in from the north on Friday morning. Have included MVFR ceilings and VCSH during that period at MCW/ALO where impacts are most likely. && .HYDROLOGY... Issued at 218 PM CDT Thu Jul 4 2024 Most area rivers continue to gradually fall, excepting a few areas mainly in the Cedar River basin where modest secondary rises are occurring. Saylorville Reservoir also continues to slowly rise, with a peak level still forecast near 878 feet on July 10-11. With scattered thunderstorms moving across the area today and seasonally high PWATs around 1.5 inches there is some risk for excessive rainfall in our northern and northeastern counties through this evening. However, the storms are expected to be fairly progressive in their movement which mitigates the threat somewhat. There is a possibility of two or more rounds of storms impacting a few areas, but even so, recovery time since last weeks heavy rains and the state of vegetation across the area also support a relatively low threat of renewed/flash flooding, at least outside of urban areas. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && DISCUSSION...Lee AVIATION...Lee HYDROLOGY...Lee
Hazardous Weather Outlook National Weather Service Des Moines IA 241 PM CDT Thu Jul 4 2024 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-051200- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene- Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper- Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union- Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne- Appanoose-Davis- 241 PM CDT Thu Jul 4 2024 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Scattered thunderstorms are forecast through this evening, first in northern Iowa this afternoon and then in northeastern and eastern Iowa before departing around sunset. Some of these storms could be strong to severe, with large hail the primary threat along with locally heavy rain. A few additional thunderstorms may enter northern Iowa from Minnesota late tonight, well after midnight. Severe weather is not expected by that time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Scattered showers and isolated thunderstorms are forecast on Friday, ending in the evening. Severe weather is not anticipated. Periodic thunderstorm chances return at times from late Saturday into the middle of next week. Any severe weather potential during this time will be better evaluated in the coming days. .SPOTTER INFORMATION STATEMENT... Spotters may be needed at times through this evening, mainly north and northeast.
Special Weather Statement National Weather Service Des Moines IA 305 PM CDT Thu Jul 4 2024 IAZ004>007-015>017-023>026-050000- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin- Including the cities of Estherville, Algona, Forest City, Lake Mills, Northwood, Manly, Emmetsburg, Garner, Britt, Kanawha, Mason City, Clear Lake, Pocahontas, Laurens, Rolfe, Fonda, Gilmore City, Humboldt, Eagle Grove, Clarion, Belmond, and Hampton 305 PM CDT Thu Jul 4 2024 ...STRONG THUNDERSTORMS POSSIBLE THIS AFTERNOON... Scattered thunderstorms will continue to persist across the area this afternoon into this evening. Small hail, gusty winds and locally heavy rainfall is expected with stronger thunderstorms. Jimenez
The Des Moines radar (KDMX), 157 km away, was scanning. The volume nearest the first event began at 21:40 UTC.
2 thunderstorm wind. Local standard time, as filed.
Delayed report of large limbs approximately 6-8 inches in diameter down on a home and power lines in Ventura. Time of occurrence estimated by radar.
Delayed report of a boat dock, tree, and garage door damage around Clear Lake. Time of occurrence estimated by radar.
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: 1199308, 1199309.