After a very brief reprieve from multiple days of activity, another round of storms greeted large parts of central Iowa during the very early morning hours of the 14th, through the rest of the morning, and into the afternoon. Traditional severe weather in the form of hail and damaging winds were sporadic, while heavy rain and flash flooding was the main player.
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.
After a very brief reprieve from multiple days of activity, another round of storms greeted large parts of central Iowa during the very early morning hours of the 14th, through the rest of the morning, and into the afternoon. Traditional severe weather in the form of hail and damaging winds were sporadic, while heavy rain and flash flooding was the main player. The hail and wind reports were low end severe with generally quarter to ping pong ball sized hail and winds less than 70 mph. Heavy rain was rather impressive with a number of spots receiving 4 to 6 inches of rain, which helped lead to periods of flash flooding.
The environment lended itself to heavy rain potential and marginal severe weather. Much of the state found itself on the cool side of a warm frontal boundary situated off to the west and the south. Given the location in relation to the warm front and nocturnal initiation, MUCAPE values were modest at best around 1000 to 2000 J/kg in central Iowa with better values to the wets and south and lesser values further north and east. Effective shear values increased through the overnight hours with aid from the nocturnal low level jet, generally finding itself in the 30 to 40+ kt range. The aforementioned nocturnal low level jet not only aided in initiation, but also ushered in plentiful moisture allowing precipitable water values to approach the 1.5 to 2.0 inch range.
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 Jun 13, 5:32 AM CST, 28 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 632 AM CDT Wed Jun 13 2018 .SHORT TERM.../Today through Tonight/ Issued at 338 AM CDT Wed Jun 13 2018 The surface boundary that is bringing much drier to the state is now over the far southeast forecast area. Dew points have fallen into the mid 50s over northwest Iowa while dew points remain in the low 70s ahead of the system. High pressure currently over eastern South Dakota will move over Iowa today and will result in a pleasant day with temperatures in the 70s to low 80s, low humidity and light winds. Despite the drier air arriving, the deeper moisture will not be displaced far with PWATs greater than 1.5 inches will be remain just to the south over Kansas and Missouri. Return flow will develop quickly as the area of high pressure moves into eastern Iowa and Illinois and will draw this moisture quickly back into the state. Strong theta-e advection will be moving into southwest Iowa between 00-06z this evening and will lead to increasing instability across the area. Thunderstorms are expected to develop and move east into central Iowa overnight. Much of this activity is not expected until after 06z. These storms will remain well elevated overnight as profiles remain mostly dry below 8 kft. While an isolated severe storm with large hail can not be ruled out, mid level lapse rates and modest MUCAPEs are not very conducive for strong/accelerating updrafts that would support severe hail. Localized rainfall amounts over 1 inch are possible. .LONG TERM.../Thursday through Tuesday/ Issued at 338 AM CDT Wed Jun 13 2018 On Thursday and Thursday night a mid-level ridge will build across the region, with warm air advection increasing across Iowa and neighboring states. Convection will fire each night in conjunction with the nocturnal LLJ, the first round lingering into Thursday morning across parts of central Iowa, and the second round mainly affecting areas just to our northeast on Thursday night/Friday morning, with the expectation that subsequent rounds of overnight/morning convection over the weekend will remain north of Iowa. Meanwhile the aforementioned ridge and warm air advection regime will lead to a pronounced heat wave across Iowa from Friday through at least Sunday, with temperatures far above normal and heat index values approaching or exceeding 100 degrees each afternoon/evening. Forecast soundings indicate potential for decent low-level mixing on these days so the resulting breezes may slightly mitigate hazardous heat effects, but given the prolonged nature of the heat it still seems probable that a heat advisory will be warranted later this week. The large mid-level ridge will gradually break down early next week, bringing an end to the heat wave and a return of rain and thunderstorm chances. However, there remains considerable uncertainty in the timing and general evolution of this breakdown. The GFS has been steadfast in bringing showers/storms and a surface trough through our forecast area on Monday/Monday night, while the ECMWF has vacillated between a similar solution and one in which the ridge holds fairly strong, delaying the trough passage and associated storms until Tuesday or even Wednesday. For now have maintained prolonged 20-40 POPs in the early part of next week, with warm temperatures on Monday moderating thereafter, but it may be several days yet before we have a better handle on this time frame. Stepping into the way-out machine, there continue to be indications that modest northwesterly flow will become established in the latter half of next week, supporting a welcome spell of relatively cooler weather, but obviously a lot can change between now and then. && .AVIATION.../For the 12Z TAFS through 12Z Thursday morning/ Issued at 632 AM CDT Wed Jun 13 2018 VFR conditions will persist through the day today along. Thunderstorms are expected across portions of central Iowa overnight, mainly after 06z. Cigs associated with the thunderstorms will remain AOA 6 kft. The wind will generally remain at less than 12 kts today and become light and variable at times by this evening. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Donavon LONG TERM...Lee AVIATION...Donavon
Hazardous Weather Outlook National Weather Service Des Moines IA 351 AM CDT Wed Jun 13 2018 IAZ004>007-015>017-023>028-033>038-044>050-057>062-070>075- 081>086-092>097-141100- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-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- 351 AM CDT Wed Jun 13 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Thunderstorm chances will increase after midnight tonight, mainly west of Interstate 35. The severe weather threat is low. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday A few thunderstorms are possible across northern Iowa late Thursday night/Friday morning and again late Friday night/Saturday morning, with a low threat of severe weather. Thunderstorm chances will then return between Monday and Tuesday, with the severe weather probability uncertain at this time. Hot and humid conditions will prevail from Friday through at least Sunday and perhaps into early next week. Heat index values will exceed 100 degrees in some areas each afternoon. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated. IAZ039-141100- Black Hawk- 351 AM CDT Wed Jun 13 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight River Flood Warnings are in effect for the Cedar River basin. Please refer to our website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday A few thunderstorms are possible across northern Iowa late Thursday night/Friday morning and again late Friday night/Saturday morning, with a low threat of severe weather. Thunderstorm chances will then return between Monday and Tuesday, with the severe weather probability uncertain at this time. Hot and humid conditions will prevail from Friday through at least Sunday and perhaps into early next week. Heat index values will exceed 100 degrees in some areas each afternoon. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated. Lee
The Des Moines radar (KDMX), 136 km away, was scanning. The volume nearest the first event began at 12:04 UTC.
31 heavy rain, 8 flash flood, 4 hail, 3 thunderstorm wind, 1 flood. Local standard time, as filed.
Coop observer reported heavy rainfall of 3.10 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.91 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.79 inches.
Minor flooding was reported along the Wapsipinicon River throughout the county and especially at Tripoli and along portions of the East Fork Wapsipinicon River throughout the county.
Public reported heavy rainfall of 2.05 inches.
Public reported heavy rainfall of 2.5 inches.
Trained spotter reported heavy rainfall of 3.65 inches.
Trained spotter reported heavy rainfall of 2.00 inches.
WHOTV relayed report of heavy rainfall of 5.70 inches.
Trained spotter reported heavy rainfall of 5.25 inches.
Trained spotter reported 2 inch diameter hail.
An NWS employee recorded heavy rainfall of 2.73 inches.
NWS employee reported heavy rainfall of 3.60 inches.
Trained spotter reported heavy rainfall of 4.50 inches.
Trained spotter reported heavy rainfall of 4.75 inches.
Trained spotter reported heavy rainfall of 5.4 inches.
Trained spotter reported heavy rainfall of 5.4 inches.
Broadcast media reported heavy rainfall of 2.50 inches.
An NWS employee reported heavy rainfall of 4.45 inches.
Public reported heavy rainfall of 2.50 inches.
Public reported heavy rainfall of 2.40 inches.
Ames Municipal Airport ASOS recorded heavy rainfall of 2.61 inches.
Trained spotter reported heavy rainfall of 2.98 inches.
Public reported heavy rainfall of 6.50 inches.
Trained spotter reported heavy rainfall of 3.7 inches.
Public reported quarter sized hail.
Public reported heavy rainfall of 3.80 inches.
Trained spotter reported heavy rainfall of 3.1 inches.
Trained spotter reported heavy rainfall of 2.63 inches.
Trained spotter reported heavy rainfall of 2.43 inches.
Public reported heavy rainfall of 3.1 inches.
Trained spotter reported heavy rainfall of 3.43 inches.
Amateur radio operator reported heavy rainfall of 2.82 inches.
Iowa Environmental Mesonet forwarded report of heavy rainfall of 5.50 inches.
Public reported ditches full and field covered in rain water. Highway 4 was partially covered with water as well.
Emergency manager reported Highway C66 near Clare closed due to flash flooding. This is a delayed report from yesterday, time estimated from radar.
Public reported quarter sized hail.
Law enforcement reported intersection of 380th St and Nelson closed due to water over the road.
Law enforcement reported water partially over the roadway.
Law enforcement reported Highway 17 closed at County Road D65 due to water over the roadway.
Trained spotter reported ping pong ball sized hail.
Trained spotter reported Highway 4 in Pocahontas was partially covered and some side streets in town were covered in water as well.
WHO-TV, via social media, reported water roughly 2 to 3 feet deep on Grand Ave at the railroad underpass just north of Lincoln Way. Several cars were stalled out in the water.
Ottumwa Regional Airport ASOS recorded a 61 mph wind gust.
Public reported water up to the bumpers on several vehicles in a parking lot near the Boone and Story county line on R38.
Public reported a large tree down over power lines.
Trained spotter reported a few large trees down on the north side of Ottumwa.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyWarnings in Iowa, June 2018
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: 762457, 762471, 762473, 767255, 762509, 762514, 762475, 762506, 762511, 762512, 762448, 762463, 762478, 762481, 762483, 762484, 762485, 762498, 762501, 762515, 762470, 762459, 762468, 762487, 762476, 762450, 762517, 762500, 762467, 762456, 762479, 762499, 762513, 762508, 765369, 762465, 762482, 762490, 762492, 762493, and more.