A line of nocturnal storms blossomed across western and southwest Iowa, remaining relatively stationary for a couple hours before slowly moving eastward through the morning hours. Some redevelopment occurred to the north, before sliding southward and weakening into the afternoon.
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 line of nocturnal storms blossomed across western and southwest Iowa, remaining relatively stationary for a couple hours before slowly moving eastward through the morning hours. Some redevelopment occurred to the north, before sliding southward and weakening into the afternoon. In all, heavy rain was the primary result with locations in excess of 4 inches and even a 7 inch report in far southern Iowa. A pair of thunderstorm wind damage reports were associated with more organized linear storm development in west central/northwest Iowa during the morning hours.
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 31, 11:00 PM CST, 1 hour 45 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1200 AM CDT Mon Aug 1 2016 .SHORT TERM.../Tonight/ Issued at 315 PM CDT Sun Jul 31 2016 Main concerns during the short term period include POP trends/placement as well as heavy rainfall potential. CWA will find itself in a broad warm air advection zone during the short term period. For the rest of this afternoon into tonight...although moisture will be plentiful...forcing will be nebulous and not focused. Thus have gone with slight chance POPs through the late evening hours. Overnight...forcing becomes more focused as the warm front to the southwest of the CWA lifts northward and LLJ develops. Combination of best moisture and forcing will be over the southwestern CWA. Isentropic lift becomes strong at the 310K surface. Warm cloud depths are progged to be at least 4 kft. Thus have gone with heavy rain wording in portions of the southwestern CWA overnight. This is also supported by WPC Day 1 excessive rainfall outlook. There is some uncertainty as to how far north the SHRA/TSRA will develop...and there is a possibility that it will develop to the southwest of present thinking...but have gone with best thoughts attm. Do not anticipate a widespread flash flood threat though...due to time of year with crop maturity. Also FFG is relatively high and would not support a widespread flash flood threat. 0-6km shear values are not high...but high enough to suggest an isolated severe threat across the southwest half. Main threats would be hail and wind. .LONG TERM.../Monday through Sunday/ Issued at 315 PM CDT Sun Jul 31 2016 A warm, humid, and fairly active week is in store for Iowa as we reside near the northern periphery of a broad mid/upper ridge covering the southern half of the CONUS. This will place us near or beneath the colloquial ring of fire with troughs in the northern stream moving across the upper Midwest and generating opportunities for convection as well as pushing weak boundaries across our region. Showers and thunderstorms associated with a warm air advection regime at the beginning of the period will be ongoing across Iowa, mainly the southern part of the state, on Monday morning. These will diminish somewhat during the day but given the instability in place the the likely presence of a residual outflow boundary retreating northward as an effective warm front, it is possible that some storms will continue to percolate during the daytime and have maintained low chance POPs to account for this. Meanwhile the first in a series of northern stream shortwaves will cross the Dakotas on Monday afternoon, generating thunderstorms that should move eastward near the IA/MN border in the late evening and nighttime hours. These will carry some severe weather risk for northern Iowa as outlined by SPC products. The outflow boundary generated by the Monday night storms across northern Iowa and minnesota will reinforce a fairly weak synoptic cool front and bring it down into Iowa, complicating the forecast for Tuesday and Wednesday. Without the influence of this boundary hot and humid weather would be a near certainty given the otherwise south southwesterly flow and warm temperatures associated with the ridge aloft. However, regions lying north of the front/outflow boundary will be somewhat cooler, though still warm, lowering confidence in the temperature forecast for these days. Also, despite the lack of an organized upper level support mechanism, enough instability will exist to support some thunderstorm development along the effective boundary, mainly during peak heating and the overnight hours both days. The result is low POPs maintained for much of this period. Forecast heat index values peak around 100 to 105 degrees across the southern half or so of our forecast area each day, but headlines are very uncertain at this point due to the marginal nature of those values and the spectre of a waffling stationary boundary and associated convection. A break in the steering pattern will finally come later in the week. On Thursday a more robust northern stream low pressure system will push a cold front across South Dakota and Minnesota, with the boundary likely crossing Iowa around Thursday night. This will probably be accompanied by more storms, and depending on its latitudinal penetration we may see a couple of days of clear and dry weather behind it around Friday/Saturday, or we may see the boundary stall around the IA/MO border and give us persisting rain chances to end the week. Either way it will bring relief from the heat for at least a couple of days and quiet weather to at least northern Iowa. && .AVIATION.../For the 06Z TAFS through 06Z Monday night/ Issued at 1200 AM CDT Mon Aug 1 2016 Clouds to increase late tonight into Monday with moisture advection into the state. Some chances for some storms across southern Iowa may impact KOTM. Confidence is less if they get into KDSM so went with a dry TAF. Otherwise winds to pick up a bit from the southeast Monday with mid/high clouds through the day. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && SHORT TERM...Zogg LONG TERM...Lee AVIATION...Beerends
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 946 PM CDT SUN JUL 31 2016 IAZ070>075-081>086-092>097-011000- CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS- MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS- 946 PM CDT SUN JUL 31 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TONIGHT THERE IS A CHANCE FOR THUNDERSTORMS LATE TONIGHT. A STRONG THUNDERSTORM WITH GUSTY WINDS WILL BE POSSIBLE. HEAVY RAINFALL IS ALSO POSSIBLE ESPECIALLY ACROSS THE SOUTHWESTERN PORTIONS OF THE AREA. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST FROM MONDAY INTO WEDNESDAY MORNING AND AGAIN FROM THURSDAY AFTERNOON THROUGH SATURDAY. STRONG TO SEVERE STORMS WILL BE POSSIBLE AT TIMES ALONG WITH LOCALLY HEAVY RAINFALL. HEAT AND HUMIDITY WILL RETURN TO CENTRAL IOWA THIS WEEK WITH HEAT INDEX VALUES POSSIBLY EXCEEDING 100 DEGREES IN THE AFTERNOON AND EVENING...ESPECIALLY WEDNESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED AT TIMES THROUGH THE WEEK. IAZ004>007-015>017-023>028-033>039-044>050-057>062-011000- 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- 946 PM CDT SUN JUL 31 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TONIGHT THERE IS A CHANCE FOR AN ISOLATED NON-SEVERE THUNDERSTORM LATE TONIGHT TOWARD SUNRISE MONDAY. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST FROM MONDAY INTO WEDNESDAY MORNING AND AGAIN FROM THURSDAY AFTERNOON THROUGH SATURDAY. STRONG TO SEVERE STORMS WILL BE POSSIBLE AT TIMES ALONG WITH LOCALLY HEAVY RAINFALL. HEAT AND HUMIDITY WILL RETURN TO CENTRAL IOWA THIS WEEK WITH HEAT INDEX VALUES POSSIBLY EXCEEDING 100 DEGREES IN THE AFTERNOON AND EVENING...ESPECIALLY WEDNESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED AT TIMES THROUGH THE WEEK. MJB
The Des Moines radar (KDMX), 140 km away, was scanning. The volume nearest the first event began at 06:46 UTC.
23 heavy rain, 2 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Coop observer measured heavy rainfall of 2.82 inches over last 24 hours, most of which came since 1:45am.
Emergency manager received report of heavy rainfall of 7 inches storm total. Exact end time of report unknown.
Emergency manager received report of heavy rainfall of 3.50 inches storm total. Exact end time of report unknown.
Emergency manager received report of heavy rainfall of 4.6 inches storm total. Exact end time of report unknown.
Emergency manager received report of heavy rainfall of 5.3 inches storm total. Exact end time of report unknown.
Emergency manager received report of heavy rainfall of 5.6 inches storm total. Exact end time of report unknown.
Emergency manager received report of heavy rainfall of 4.5 inches storm total. Exact end time of report unknown.
Coop observer measured heavy rainfall of 4.25 inches over last 24 hours, most of which since 2:45am.
Public reported heavy rainfall of 4.1 inches storm total.
Home weather station accumulation measured since about 3:15am.
CoCoRaHS observer reported heavy rainfall of 4.25 inches since about 3:15am.
Emergency manager received report of heavy rainfall of 3.00 inches storm total. Exact end time of report unknown.
Trained spotter reported heavy rainfall of 4.50 inches storm total.
Greenfield LARC measured 2.10 inches of rainfall over last 24 hours. Most of which came after 3:30am.
Coop observer measured 2.60 inches of rainfall over last 24 hours, most of which came since 3:30 am.
Home weather station accumulation since 3:30am.
Trained spotter reported heavy rainfall of 2.6 inches storm total.
Emergency manager received report of heavy rainfall of 4.4 inches storm total. Exact end time of report unknown.
WHO relayed viewer measured heavy rainfall of 5.20 inches.
KCCI relayed a viewer measured heavy rainfall amount of 4.66 inches.
Trained spotter reported heavy rainfall of 2.91 inches with rain beginning approximately at 430 am.
Coop observer recorded heavy rainfall of 2.10 inches over the last 24 hours, primarily falling on the first.
Coop observer recorded heavy rainfall of 2.50 inches over last 24 hours, primarily falling on the first.
Public reported several trees up to one foot in diameter down near Schaller. Time and location estimated from radar and reported via social media.
Public reported numerous trees with diameter upwards of one foot down around Lake view. Tree reported downed onto truck. Time and location estimated from radar.
Coop observer reported widespread water covering roadways throughout Mount Ayr. Water over roadways was upwards of 6+ inches deep. Time and locations estimated.
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: 650428, 650439, 650438, 650445, 650440, 650441, 650444, 650427, 650437, 650430, 650434, 650443, 650448, 650425, 650426, 650429, 650436, 650442, 650447, 650446, 650449, 650467, 650468, 650431, 650432, 650435.