A nearly stationary boundary combined with heating resulting in an area of thunderstorms with several storms becoming severe. Large hail and a couple of damaging winds reports were received.
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 DVN wrote it up.
A nearly stationary boundary combined with heating resulting in an area of thunderstorms with several storms becoming severe. Large hail and a couple of damaging winds reports were received.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at May 13, 10:52 AM CST, 2 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 1152 AM CDT Sun May 13 2018 ...LATE MORNING HYDROLOGY UPDATE... .SYNOPSIS... Issued at 255 AM CDT Sun May 13 2018 Isolated showers were ongoing late tonight mostly between highway 20 and I-80. A new cluster of elevated showers and storms has developed on the nose of an 850mb low-level jet and on gradient of northward WV transport over central Iowa. This cluster is not severe, but poses a lightning, small hail, and heavy rain risk with hourly rainfall rates peaking near 1" based on dual-pol and MRMS radar data. Westerly 850-300mb mean flow will take the organized showers and storms generally along I-80 through the remainder of tonight into early Sunday morning. && .SHORT TERM...(Today and Tonight) ISSUED AT 255 AM CDT Sun May 13 2018 Today After the early morning showers and storms fall apart, we'll be looking at a nice day with warmer temperatures into the 60s and 70s for most areas. Chances for additional showers and storms through the day are low. Tonight There is a Slight risk for severe storms over portions of east- central Iowa and northwestern Illinois. The main threats are damaging winds and large hail. Heavy rain rates are also possible. Convergence on the northern edge of an increasing low-level jet and building instability through impressive surface-850mb water vapor transport will lead to convective initiation after across north-central Iowa after 9-10 PM. Deep layer shear near 40 kts and moderate instability with MUCAPE values of 1000-2000 J/kg will favor organized storm structures. Additionally, southerly surface flow and rising dewpoints into the 60s means there will also be some surface-based CAPE. Mean layer flow and forward-propagating Corfidi vectors would steer potential MCS to the ENE, but surface theta-e gradient has a SE trajectory into northwestern Illinois and storm complexes tend to follow closely to the latter. So there is uncertainty regarding how far south the storms track tonight, but again the Slight risk for severe storms is approximately in the counties along and north of I-80, most likely after midnight. Uttech .LONG TERM...(Monday through Saturday) ISSUED AT 255 AM CDT Sun May 13 2018 An extended period of summer-like temperatures and more periods of showers and storms are the highlights of the long-term forecast period. Monday: Early Monday, remnants of an overnight thunderstorm complex are possible across northeast portions of the forecast area. Monday afternoon and night, much of the forecast area except for the far northern and eastern fringes is in a slight risk for severe storms. An airmass characterized by PWAT's around 2 inches and SBCAPE around 3000 j/kg will be supportive of precip-loaded storms with a wind and heavy rain threat. The Namnest simulated reflectivity suggests discrete storms firing near the boundary in the late afternoon then coalescing into a linear complex during the evening. The tornado threat does not look very impressive right now but will need to watch storms near the boundary closely. Wind damage and flash flooding may be the biggest threats. Tuesday: Scattered showers and storms are expected to linger north of the front, but weak deep-layer shear should preclude any severe weather. Above normal temperatures will continue with highs in the upper 70s/low 80s. Wednesday through Saturday: Lack of consensus among the synoptic models leads to low forecast confidence this period. The ECMWF and GEM are mainly dry until Saturday with the main energy well to the south. The GFS has a more pronounced slow moving upper trough in the region and rain chances every day but Saturday. Blended pops are favoring the drier solutions. Warm temperatures will persist, with highs in the upper 70s and 80s and lows in the 50s to low 60s. && .AVIATION...(For the 12Z TAFS through 12Z Monday Morning) ISSUED AT 642 AM CDT Sun May 13 2018 IFR/LIFR ceilings will improve through the morning to MVFR/IFR. Showers and storms currently over parts of E Iowa/NW Illinois will diminish over the next few hours. Then an upper disturbance moving in from W Iowa may kick off a batch of showers and isolated weak storms during the early to mid afternoon. A more substantial round of storms is expected tonight, some of which could produce severe weather. For now, included PROB30 groups for tonight due to low confidence on exact placement and timing of storms. Uttech && .HYDROLOGY... Issued at 1146 AM CDT Sun May 13 2018 On the Mississippi...the crest appears to be progressing south of LD 16 IL City and through Muscatine, New Boston, Keithsburg, Gladstone, and on the doorstep of Burlington today. New Boston looks to be cresting out just under the Major flood stage, while Burlington is nearing crest at a little above Major flood stage. The last site to experience the crest still appears to be Gregory Landing on Tuesday. Sites from the Quad Cites on north are continuing to fall, with the next site projected to fall below flood stage being LD 11 at Dubuque later tonight. Concerning the tributaries...flood warnings continue for just a few sites along portions of the lower ends of the Iowa and Wapsipinicon Rivers, as rainfall runoff continues to route through these tributary systems. Depending on the extent of rainfall falling on the various tributary basins over the next several days, other sites may experience withing bank rises or even approach flood stage. The rivers already in flood will also have to be watched for slowed post- crest recessions or secondary crests developing. But on the larger watershed of the mainstem Mississippi River, the rounds of rainfall with the passing storm occurrences over the next several days, are still only expected to delay or slow the river level recessions after the crests occur. ..12.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...Uttech SHORT TERM...Uttech LONG TERM...RP Kinney AVIATION...Uttech HYDROLOGY...12
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 342 AM CDT Sun May 13 2018 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-140845- Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson- Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson- Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll- Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson- Warren-Hancock-McDonough-Scotland-Clark- 342 AM CDT Sun May 13 2018 This Hazardous Weather Outlook is for portions of north central Illinois...northwest Illinois...west central Illinois...east central Iowa...northeast Iowa...southeast Iowa and northeast Missouri. .DAY ONE...TODAY AND TONIGHT The Storm Prediction Center has a Slight risk for severe storms mainly in the counties along and north of I-80. The primary threats are damaging winds and large hail. Heavy rain rates of 1 to 1.5 inch per hour are also possible with the strongest storms. The most likely time frame for storms is between midnight and 6 AM. Flooding will continue along the Mississippi River and portions of the Cedar, Iowa, and Wapsipinicon Rivers. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY The Storm Prediction Center has a Slight risk for severe storms Monday and Monday night over much of the outlook area, with a Marginal risk from Independence, to Freeport and Princeton Illinois. The primary threats are damaging wind gusts and flash flooding. Scattered non-severe thunderstorms are expected Tuesday. There is a low chance of thunderstorms Wednesday through Saturday. Flooding will continue along the Mississippi River and portions of the Cedar, Iowa, and Wapsipinicon Rivers. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed tonight. Uttech/RP Kinney
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
912 AM CDT SUN MAY 13 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 AM HEAVY RAIN 2 W GENOA BLUFF 41.72N 92.18W
05/13/2018 E1.50 INCH IOWA IA TRAINED SPOTTER
&&Special Weather Statement National Weather Service Quad Cities IA/IL 133 PM CDT SUN MAY 13 2018 IAC107-131915- Keokuk- 133 PM CDT SUN MAY 13 2018 ...A STRONG THUNDERSTORM WITH HAIL AND FREQUENT LIGHTNING WILL AFFECT KEOKUK COUNTY UNTIL 215 PM CDT At 132 PM CDT, a strong thunderstorm was located near Oskaloosa, moving east at 45 mph. Nickel size hail is possible with this storm. Locations impacted include... Sigourney, What Cheer, Delta, Keswick, South English, Harper, Kinross, Hayesville, Keota, Ollie, Webster, Sig-Nor Field Airport, Lancaster, Keokuk County Expo, Lake Belva Deer Park, Yenruogis County Park, Sigourney Iowa Airport, Talleyrand and Keokuk County Fairgrounds. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. LAT...LON 4143 9241 4149 9195 4120 9195 4118 9241 TIME...MOT...LOC 1832Z 257DEG 39KT 4128 9252 McClure
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
203 PM CDT SUN MAY 13 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0155 PM HAIL 0.5 W SIGOURNEY 41.33N 92.22W
05/13/2018 M0.25 INCH KEOKUK IA TRAINED SPOTTER
&&Special Weather Statement National Weather Service Quad Cities IA IL 211 PM CDT Sun May 13 2018 IAZ040-041-051-052-063-064-076-077-132115- Buchanan-Delaware-Benton-Linn-Iowa-Johnson-Keokuk-Washington- Including the cities of Independence, Manchester, Vinton, Cedar Rapids, Marengo, Iowa City, Sigourney, and Washington 211 PM CDT Sun May 13 2018 ...A Period of Strong Winds Expected Through 4 PM... Strong southeast to south winds will develop on the backside of showers and thunderstorms. These winds will gust between 35 mph to 50 mph, and will make travel difficult for those in high profile vehicles on east...west roadways. In addition these winds may blow around loose outdoor objects and possibly down small branches. Be prepared for these strong winds gusts for a time this afternoon.
Special Weather Statement National Weather Service Quad Cities IA/IL 214 PM CDT SUN MAY 13 2018 IAC107-183-132000- Keokuk-Washington- 214 PM CDT SUN MAY 13 2018 ...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN KEOKUK AND WASHINGTON COUNTIES UNTIL 300 PM CDT At 214 PM CDT, a strong thunderstorm was located near Richland, or 12 miles east of Sigourney, moving east at 45 mph. Wind gusts of 50 to 55 mph and nickel size hail are possible with this storm. This storm will be near... Brighton around 225 PM CDT. Washington around 235 PM CDT. Ainsworth and Crawfordsville around 245 PM CDT. Other locations impacted by this storm include Haskins, Ollie, West Chester, Noble, Lake Darling State Park, Washington Airport, Lancaster, Talleyrand, Washington County Fairgrounds and Marr Park. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. LAT...LON 4133 9216 4141 9148 4116 9149 4116 9220 TIME...MOT...LOC 1914Z 260DEG 39KT 4127 9199 McClure
The Quad Cities radar (KDVN), 99 km away, was scanning. The volume nearest the first event began at 19:33 UTC.
11 hail, 2 thunderstorm wind. Local standard time, as filed.
A delayed report was received from the public of a small tree down.
A trained spotter reported dime to nickel sized hail.
Received an amateur radio report of nickel sized hail six miles southwest of Washington on Highway 1.
The county emergency manager reported penny sized hail.
A public report was received of penny sized hail.
Received a report from local media of penny sized hail.
A trained spotter reported hail up to the size of quarters.
Received a public report of golf ball sized hail. The time was estimated based on radar and another nearby hail report.
A trained spotter reported hail up to the size of half dollars.
A trained spotter reported hail up to the size of quarters. The time was estimated by radar.
A trained spotter reported hail up to the size of nickels. The hail started as pea sized and increased to the size of nickels before it quit.
A public report was received of hail up to the size of nickels that last for 5 minutes.
A trained spotter reported wind gusts 4 WSW of Mount Union of 50 up to 60 mph. Hail up to the size of pennies was also reported.
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, May 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: 749723, 749710, 749713, 749714, 749715, 749716, 749717, 749718, 749719, 749720, 749721, 749722, 760555.