A hot a humid air mass led to scattered thunderstorms the morning and afternoon of June 14th, 2017. The scattered thunderstorms brought heavy rain rates, and spotty severe weather reports across eastern Iowa, northwest Illinois, and northeast Missouri.
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 hot a humid air mass led to scattered thunderstorms the morning and afternoon of June 14th, 2017. The scattered thunderstorms brought heavy rain rates, and spotty severe weather reports across eastern Iowa, northwest Illinois, and northeast Missouri. The most significant severe weather occurred late in the afternoon, as storms moved east across Bureau and Putnam Counties into La Salle County.
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 Jun 14, 3:01 AM CST, 1 hour 19 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 401 AM CDT Wed Jun 14 2017 .SYNOPSIS... Issued at 359 AM CDT Wed Jun 14 2017 Several large storm complexes continued tonight well to our west from The MN arrowhead across MN, western IA into northeast MO and eastern KS. These were on the edge of the cyclonic flow aloft between the large upper low over western ND and a flattening upper level ridge axis from the mid MS valley into the Great Lakes region. Trends so far tonight have been for outflow boundaries from reforming storm complexes over western IA to dissipate as they advance eastward away from the elevated moisture transport and into the less favorable, mostly capped and weakly sheared environment over eastern IA. At the surface, it remained very warm and somewhat humid with 3 am temperatures in the 70s and dewpoints in the upper 60s to around 70 with light southerly winds under increasing upper level clouds from the upstream convection. && .SHORT TERM...(Today and Tonight) ISSUED AT 359 AM CDT Wed Jun 14 2017 Main focus is on convective trends as the overall setup becomes much more favorable for thunderstorms than the area has seen over the past week. There is a potential for some storms to be strong to severe, and SPC maintains a slight risk over the entire forecast area. The upper level ridge, and capping dome of very warm air aloft will continue to break down today as the upper level flow becomes more zonal. This will allow the weak surface front, that has lingered out west the past several days to push east through the area tonight acting as the primary trigger for showers and thunderstorms. Ahead of this, potential outflow boundaries and forcing from one or more convectively induced shortwaves out over the plains will be the driver of convective trends today. In the near term, a weak outflow boundary about to enter our northwest and new one taking shape over central IA will be the primary triggers for thunderstorms as they proceed E-SE into the forecast area early this morning. Confidence in how long these boundaries hold together and their potential to trigger more than isolated showers and thunderstorms over the local area remains low. Convective allowing high res models tonight have had a poor handle on this evolution and offer differing scenarios, with some triggering new rounds of widespread storms over the MS valley within the next several hours and others remaining dry. Instead of biting off on a low confidence specific solution, will keep a broad brush approach with widespread chance pops going for the forecast area this morning and continue to monitor trends for more specific updates. Later today, there will likely be a back edge of the high level cloud cover from upstream convection providing sunshine by late morning and early afternoon, leading to further destabilization and renewed convection along boundaries. There will be a focusing upper level shortwave to trigger more organized activity in the afternoon into early evening, with the cold front sweeping through overnight to end the precipitation potential from northwest to southeast. Will stay with high chance pops during the afternoon, then a period of likely pops in the evening hours over the east. As far as the severe potential: storms this morning will mainly be outflow dominated with wind gusts of 40 plus mph the main concern. This afternoon and evening, with storms developing in a high instability, but modest shear environment, any boundaries will be critical for possible supercell development with associated threats of large hail and damaging wind and a very low potential for tornadoes. Otherwise, the main threats will be bowing segments in mostly linear storm complexes capable of producing damaging winds. Temperatures will be highly dependent on cloud cover and have stayed conservative with highs in the upper 80s to around 90. With dewpoints holding in the upper 60s to around 70, max heat index values will push the lower to mid 90s, which would be slightly lower than the past couple days. .LONG TERM...(Thursday through Tuesday) ISSUED AT 359 AM CDT Wed Jun 14 2017 Thursday Hot and dry in the lower 90s on avg across E Iowa/NW Illinois. Went a few degrees above the blended guidance because the drier air will be easier to heat up. The warmest temps should coincide with a +20 C 850mb thermal ridge forecast to overspread the SW half of the CWA during the mid to late afternoon. Have highs between 92-94 F in this area. Fortunately, dewpoints will fall into the 60s and 50s for most locations, which will cap heat indices at or a few degrees below the ambient air temps. For Thursday evening and night, there are major differences regarding convection. NAM/GFS are much more aggressive than the ECMWF/CMC. Current forecast has 30-40% PoPs and overall confidence is low. One possible scenario is a mid-level vorticity max provides enough ascent to focus convective development along a low-level boundary, and on the northern edge of the cap, during the late afternoon from NE Iowa into north-central Kansas. This scattered convection may then propagate to the ESE into the DVN CWA. The overall severe weather threat appears low, but a few strong storms are possible, especially in the counties along and south of highway 34. Friday Increasing humidity as dewpoints rise back into the 60s. For temps, the model blend has highs in the mid to upper 80s. Another vort. max progged to quickly translate through the Central Plains into the Upper Mississippi Valley. Latest model guidance indicates the greatest chance for thunderstorms is Friday evening or night when the nocturnal low-level jet ramps up. However, 20-30% PoPs are going through the day, increasing to 30-50% at night. Environmental kinematics (0-6 km bulk shear +35 kts) and thermodynamics are favorable for some strong or severe thunderstorms. Since this is several days away, the details on timing and coverage are unclear. Saturday We repeat the process again on Saturday with yet another chance for showers and thunderstorms - best chances are during the evening and overnight. We'll have to monitor for severe potential because a hot and humid air mass will be present when a stronger trough drops in from the NW. The trough will increase deep layer shear significantly by the mid to late evening. Sunday through Wednesday Models in agreement on a pattern change to NW 850-500mb flow and near normal temps/lower humidity. Aside from occasional low chances for light showers, much of this 4 day stretch looks dry. The overall threat for heavy rain is very low. Uttech && .AVIATION...(For the 06Z TAFS through 06Z Wednesday Night) ISSUED AT 1147 PM CDT Tue Jun 13 2017 Convective allowing models continue to have a wide variety of solutions in regards to convective coverage and timing overnight through Wednesday. Have opted for a 4-hr tempo group overnight at each site to handle initial batch of storms moving into central Iowa at this time. Additional rounds could develop later Wednesday morning and again Wednesday afternoon. Did not want to depict such a lengthy period of storm chances with such low confidence, and have emphasized the afternoon period with VCTS groups. Ceilings will be mainly low VFR with some lower visibilities in more intense storms. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...Sheets SHORT TERM...Sheets LONG TERM...Uttech AVIATION...RP Kinney
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 505 AM CDT Wed Jun 14 2017 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-151015- 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- 505 AM CDT Wed Jun 14 2017 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 Severe thunderstorms are possible today and tonight. The Storm Prediction Center has a slight risk over the entire outlook area. Scattered thunderstorms early this morning may produce small hail, heavy downpours and wind gusts up to 40 mph, especially over eastern Iowa. Severe thunderstorms with damaging wind, large hail and isolated tornadoes will be more likely in the afternoon and early evening hours over the entire outlook area. Hot and humid conditions are expected again today with heat index readings as high as the mid 90s this afternoon. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY There are periodic chances for thunderstorms Thursday night through Saturday night. For the first round Thursday night into early Friday morning, a few strong storms are possible in the counties along and south of highway 34. The main threats are strong wind gusts and lightning. There is a marginal risk for severe thunderstorms on Friday across the entire outlook area. The best chance for storms is Friday evening or Friday night. Damaging winds and large hail are possible with the strongest storms. Thunderstorm coverage will likely remain scattered. Strong or severe thunderstorms are possible Saturday afternoon into Saturday night. However, confidence is low with respect to timing and areal coverage. Please stay tuned to forecast updates through this week. .SPOTTER INFORMATION STATEMENT... Storm spotter activation may be needed this afternoon and evening. Sheets/Uttech
The Quad Cities radar (KDVN), 125 km away, was scanning. The volume nearest the first event began at 10:18 UTC.
11 hail, 8 thunderstorm wind. Local standard time, as filed.
Wind gusts were estimated to be 60 to 65 mph on the gust front of the storm, and this downed multiple trees in town. One tree fell onto power lines causing the pole to snap. Time estimated from radar data.
Small limbs were reported blown down.
A semi was blown over on Highway 13 from thunderstorm outflow winds. The time was estimated from radar data.
The public reported several trees snapped in half between 19th street and Blairs Ferry road. The time was estimated from radar data.
A 8 to 10 inch diameter tree snapped at base. The time was estimated from radar data.
Tree limbs were reported down in southeast corner of Mt Vernon and power was knocked out to the city of Mt Vernon.
A residential swing set was damaged.
A spotter estimated winds of 60 mph.
Trained spotters reported numerous hail reports of 1 to 1.75 inch diameter hail across central and eastern Dubuque County, including the city of Dubuque.
The hail lasted for 5 minutes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2017Every state in 2017This day in weather historyWarnings in Iowa, June 2017
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: 693411, 693409, 693407, 693410, 693408, 744391, 700642, 693412, 693404, 693405, 700634, 693406, 700635, 700636, 700637, 700638, 700639, 700640, 700641.