A few thunderstorms initiated ahead of a cold front through portions of central Iowa, within a warm and moist environment, ripe with dew points into mid and upper 70s. A couple of the morning thunderstorms were able to produce damaging winds, while thunderstorms associated with the cold front later that evening produced a few more damaging wind reports.
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 DMX wrote it up.
A few thunderstorms initiated ahead of a cold front through portions of central Iowa, within a warm and moist environment, ripe with dew points into mid and upper 70s. A couple of the morning thunderstorms were able to produce damaging winds, while thunderstorms associated with the cold front later that evening produced a few more damaging wind reports. Overall, most damage consisted of tree branches, with a few small trees snapped or uprooted as well.
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 Aug 4, 5:50 AM CST, 3 hours 40 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 650 AM CDT Thu Aug 4 2016 ...Updated Aviation Discussion... .SHORT TERM.../Today/ Issued at 409 AM CDT Thu Aug 4 2016 Main forecast concern was focused on timing of convection and any severe weather potential. Pulled back the onset of pops a few hours today and confined them to just the north to northwest this morning. The MCS over east-central South Dakota looks to move into northern portions of the CWA b/t 13-15z this morning and will be the first round of storms. The second round looks to develop along the cold front this afternoon. Most of the hires models agree on this timing, but keep convection somewhat disorganized and thus low confidence any widespread severe potential this morning. The cold front looks to enter the northwest portion of Iowa b/t 18-21z and transition southeast through the afternoon hours and by around 00z Friday it looks to be located from near Cass County to Black Hawk County. The better forcing remains over northern Iowa collocated with good instability. MCW NAM/GFS Bufr soundings suggest SB CAPE to increase to 3000-4000 J/kg b/t 21-00z today. Low level shear is weak, 0-1km is roughly 10 knots and 0-3km shear is near 20 knots and thus not anticipating much of a tornado threat today. Main severe concern would be elevated hail and damaging wind with the amount of instability present, including DCAPE values over 1000 J/kg, once storms redevelop later this afternoon. The other threat is heavy rain as PWATs are as high as 2.5 inches and warm layer cloud depths over 14,000 feet. Certainly anything that develops will have the potential to put down a significant amount of rain in a short time frame. The coverage looks to be limited until after 00z Friday. .LONG TERM.../Tonight through Wednesday/ Issued at 409 AM CDT Thu Aug 4 2016 The cold front will be entering central Iowa by 00z with thunderstorms likely ongoing to begin the period in vicinity of the boundary especially over the northeast. A possible split may be in progress with the primary upper level system and kinematics passing to the north while other energy remains to the southwest. This line should eventually fill during the evening as the system settles slowly south. Heavy rain potential remains with a ribbon of PWATs in excess of 2 inches pooling ahead of the front. Despite the lack of a good LLJ development this evening, moisture transport will remain good in the low to mid levels feeding into the boundary. Initial storm motions will be nearly parallel to the front leading to the potential for training of storms. A few severe storms remain possible with best potential over the northeast half of the state where better deep layer shear resides. Damaging wind gusts remain the main threat for severe weather with cold pool development possible with favorable 0-3 km theta-e differences and flow becoming unidirectional aloft. Convection may maintain much of the night as the cold front settles very slowly south and instability remaining a bit post frontal keeping thunderstorm chances going despite boundary passage. Showers and thunderstorms will remain possible over the far south on Friday. There is some uncertainty farther north towards the I80 corridor where good drying is taking place below 700 mb but good deep layer moisture will reside above this level along with continued weak forcing. May need to add a few showers back north if trends persist. The moisture aloft and associated clouds may also keep temperatures cooler than the forecast upper 70s to lower 80s over the southern half. Additional chances for showers and isolated thunderstorms will try to lift into southwest Iowa Saturday while pleasant and dry conditions are expected elsewhere. The best potential for thunderstorms over the weekend remains late Sunday into Monday morning as warm advection begins to surge back north. Tuesday and Wednesday will be warm and humid with a few isolated storms possible. && .AVIATION.../For the 12Z TAFS through 12Z Friday morning/ Issued at 650 AM CDT Thu Aug 4 2016 VFR conditions look to prevail through the TAF period with storms chances this afternoon and evening. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && SHORT TERM...Podrazik LONG TERM...Donavon AVIATION...Podrazik
HAZARDOUS WEATHER OUTLOOK...RETRANSMITTED NATIONAL WEATHER SERVICE DES MOINES IA 512 AM CDT THU AUG 4 2016 IAZ004>007-015>017-023>028-034>039-046>050-060>062-051015- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-CALHOUN-WEBSTER- HAMILTON-HARDIN-GRUNDY-BLACK HAWK-GREENE-BOONE-STORY-MARSHALL- TAMA-POLK-JASPER-POWESHIEK- 512 AM CDT THU AUG 4 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND NORTH CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE POSSIBLE THIS MORNING THEN AGAIN THIS AFTERNOON AND EARLY EVENING. A FEW SEVERE STORMS MAY OCCUR WITH LARGE HAIL AND DAMAGING WINDS THE MAIN THREATS. HEAVY RAINFALL IS ALSO POSSIBLE ALONG WITH LOCALIZED FLASH FLOODING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST AT TIMES SUNDAY THROUGH MONDAY NIGHT WITH MORE ISOLATED ACTIVITY TUESDAY AND WEDNESDAY. SEVERE WEATHER AND HEAVY RAINFALL MAY BE POSSIBLE MAINLY BETWEEN SUNDAY AND MONDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME HOWEVER RAINFALL AND FLOODING REPORTS ARE ENCOURAGED. IAZ033-044-045-057>059-070>075-081>086-092>097-051015- SAC-CRAWFORD-CARROLL-AUDUBON-GUTHRIE-DALLAS-CASS-ADAIR-MADISON- WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO- TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS- 512 AM CDT THU AUG 4 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND SOUTH CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE POSSIBLE LATER THIS AFTERNOON AND OVERNIGHT. ISOLATED SEVERE STORMS MAY OCCUR WITH LARGE HAIL AND DAMAGING WINDS THE MAIN THREATS. HEAVY RAINFALL IS ALSO POSSIBLE ALONG WITH LOCALIZED FLASH FLOODING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY SCATTERED THUNDERSTORMS ARE EXPECTED LATE THURSDAY INTO THURSDAY NIGHT. A FEW STRONG TO SEVERE STORMS PRODUCING GUSTY WINDS AND LOCALLY HEAVY RAIN ARE POSSIBLE. ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST AT TIMES SATURDAY NIGHT THROUGH MONDAY NIGHT WITH MORE ISOLATED ACTIVITY TUESDAY AND WEDNESDAY. SEVERE WEATHER AND HEAVY RAINFALL MAY BE POSSIBLE MAINLY BETWEEN SUNDAY AND MONDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME HOWEVER RAINFALL AND FLOODING REPORTS ARE ENCOURAGED.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
1009 AM CDT THU AUG 4 2016
IAZ017-026-027-041545-
FRANKLIN IA-CERRO GORDO IA-BUTLER IA-
1009 AM CDT THU AUG 4 2016
...GUSTY WINDS AND DIME HAIL POSSIBLE...
AT 1008 AM CDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM
OVER ROCKWELL...OR 11 MILES SOUTH OF MASON CITY...MOVING EAST AT 25
MPH.
DIME SIZE HAIL AND WIND GUSTS UP TO 50 MPH WILL BE POSSIBLE WITH THIS
STORM.
LOCATIONS IMPACTED INCLUDE...
MASON CITY...SHEFFIELD...ROCKWELL...THORNTON...SWALEDALE...CHAPIN...
AREDALE...DOUGHERTY...BURCHINAL AND PORTLAND.
LAT...LON 4291 9303 4291 9290 4285 9287 4281 9336
4307 9344 4320 9303
TIME...MOT...LOC 1508Z 257DEG 21KT 4298 9321
BEERENDSThe Des Moines radar (KDMX), 145 km away, was scanning. The volume nearest the first event began at 15:33 UTC.
7 thunderstorm wind, 1 heavy rain, 1 funnel cloud. Local standard time, as filed.
KWWL recorded heavy rainfall of 2.77 inches. Came in two waves, morning storm followed by evening storms.
Trained spotter reported a 2 foot diameter tree snapped.
Media reported a large tree down on some power lines. Delayed report.
Trained spotter reported multiple trees and tree limbs downed in Washburn, as well as a small metal roof canopy flipped. Time estimated from radar, and delayed report.
Trained spotter reported 1 foot diameter tree limbs blown off of tree.
Trained spotter reported estimated 65 mph wind gust.
Trained spotter reported strong winds estimated to be around 70 mph with many large limbs down.
Local newspaper reported at least 15 to 20 trees down across the northern side of Grinnell, some 3 to 4 feet in diameter. Multiple trees fell and damaged building and house roofs. At least 12000 people without power in the area. Delayed report, and time estimated from radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2016Every state in 2016This day in weather historyWarnings in Iowa, August 2016
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: 654543, 654537, 654538, 654539, 655500, 654540, 654541, 655498, 654542.