More heavy rainfall was seen across the area, primarily situated over the northern third of the state, as a surface boundary sat across central Iowa and a shortwave moved through the upper level flow. 7 inches, moderate to strong low level moisture flow, modest MUCAPE around 500-1000+ J/kg, strong bulk effective shear of 40 to 60 kts, and continued lifting mechanisms from the aforementioned…
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.
More heavy rainfall was seen across the area, primarily situated over the northern third of the state, as a surface boundary sat across central Iowa and a shortwave moved through the upper level flow. Overall, conditions remained ripe and very much summer-like as opposed to mid-September including precipitable water values were around and in excess of 1.7 inches, moderate to strong low level moisture flow, modest MUCAPE around 500-1000+ J/kg, strong bulk effective shear of 40 to 60 kts, and continued lifting mechanisms from the aforementioned surface boundary and upper level short wave.
Over a roughly 24 hour period, a number of sites experienced havy rainfall in the 3 to 4 inch range, with a few reporting as much as 5+ inches. Fortunately, with widespread precipitation and limited instability, storms remained sub-severe during this portion of the heavy rainfall event. By late afternoon and evening, as the surface low progressed across the area, stronger, more organized convection moved across the area and produced severe winds. The severe wind event will be covered by another entry focused on September 20th.
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 Sep 18, 10:37 PM CST, 24 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1137 PM CDT Tue Sep 18 2018 .DISCUSSION.../Tonight through Tuesday/ Issued at 414 PM CDT Tue Sep 18 2018 At 20z Tue, a somewhat broad, stretched more northerly-southerly, area of anticyclonic flow was centered over eastern Oklahoma. Meanwhile height falls were noted across the western Plains as low pressure has begun to try to establish itself off the Rockies. With this synoptic setup, moisture was being transported from the Gulf of Mexico through West Texas and into Kansas. As this anticyclone propagates eastward the next couple of days, low- level moisture transport will make it into Iowa. Mesoscale has dominated as an outflow boundary went pushed southward all the way from northern Iowa into Missouri. Behind this boundary, clouds kept temperatures down... confining highs to the 60s... where southern Iowa made it into the low 90s before the boundary arrived there. The RAP has had the best handle on the progression of this boundary, so have leaned towards it much of the day. For this evening into tonight... PWAT values continue to push 2 inches across most of Iowa through the next couple of days. A Theta- e ridge has begun to build over eastern Nebraska, with the ribbon cutting right through western Iowa. A 30 KT 850mb LLJ pokes its way into NW Iowa after 06z Wed. In short, severe threat will diminish to nil overnight as MUCAPE values drop to around 500 J/KG. Main focus is on flooding potential. Northern/NW Iowa has had generally 1 to 2 inches of rain the past 48 hours, with some locations closer to Mason City approaching 3 to 4 inches this morning alone. The GFS is excited about orienting a band of E-W oriented 925mb frontogenetical forcing to serve as a focusing mechanism for where reinforcing precip could set up and dump itself. At this time, think NW Iowa is the most likely location for best phasing. Again, if this shifts eastward closer to I-35 and especially Mason City, would need to be quick on trigger for Flash Flooding headlines. Tomorrow... May be somewhat a repeat of today. Will be watching for an outflow boundary to kick off the overnight convection and sag southward. The difference in the setup tomorrow is that as the LLJ cuts into Iowa, this boundary will not drop all the way into Missouri. Rather, it will take a slightly more NW-SE orientation. There will be a remarkable temperature difference north/south of the boundary. Highs south of the boundary will be into the 90s, highs north of the boundary may struggle to make it into the 70s again. Heat index values south of the boundary will likely be in the low to upper 90s... opening the door for possible heat-related issues in southern Iowa. Instability south of the boundary very high as MUCAPE values approach 3000 J/KG. Low-level lapse rates also very steep, so hail would be a primary threat, along with damaging winds. Like today, thunderstorms may produce periods of heavy rain. Thursday into the weekend... All eyes shift to the cold fropa as a sfc low finally gets its act together and pushes through the upper midwest. The past several 12z/00z model runs have trended to slow the progression of the cold front. This is notable as the timing of the fropa may now not be until 03z Fri-09z Fri at the earliest... which would put us out of a lot of the daytime heating convection. Thunderstorms are very likely with this fropa, including severe weather. With the focus on the near-term... the Thursday fropa will be detailed in higher resolution over time. Seasonable temperatures return to Iowa this weekend as conditions should dry out through Saturday. && .AVIATION.../For the 06Z TAFS through 06Z Wednesday night/ Issued at 1136 PM CDT Tue Sep 18 2018 Similar concerns to previous package. Convection near KOMA slowly increasing. H850 flow likely to increase over NE/NW Iowa from 08-12z resulting in another larger storm complex moving across north sites KFOD/KMCW/KALO from 09-16z with lesser chances for KDSM/KOTM. From 06z through 08z sct activity at these two sites may cause temp impacts. 2-5SM br also expected with locally lower vsby west of KDSM through 13z. Expecting a break aft 16z with convection lessening in coverage north aft 18z...but may still be impacting KFOD/KMCW/KALO through 00z. Confidence lower aft 18z. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && DISCUSSION...Kotenberg AVIATION...REV
Hazardous Weather Outlook National Weather Service Des Moines IA 426 PM CDT Tue Sep 18 2018 IAZ004>007-015>017-023>028-033>039-192130- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk- 426 PM CDT Tue Sep 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Tonight Thunderstorms are forecast tonight. A few storms may be strong, with the potential for locally heavy rainfall and associated water issues including flooding possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are possible Wednesday and Thursday. A few storms may be strong on Wednesday. A few storms may be strong to severe on Thursday, with damaging winds and large hail the primary threats. Heavy rainfall that may lead to flash flooding is possible, especially in locations that receive heavy rainfall tonight. .SPOTTER INFORMATION STATEMENT... Any rainfall and/or severe weather reports are welcome. Spotter activation is not anticipated at this time. IAZ044>050-057>062-070>075-081>086-092>097-192130- 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- 426 PM CDT Tue Sep 18 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Tonight Non-severe thunderstorms are possible tonight, especially towards central to northern Iowa. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are possible Wednesday and Thursday. A few storms may be strong on Wednesday. A few storms may be strong to severe on Thursday, especially in western Iowa, with damaging winds and large hail the primary threats. .SPOTTER INFORMATION STATEMENT... Any rainfall and/or severe weather reports are welcome. Spotter activation is not anticipated at this time. Kotenberg
Special Weather Statement
National Weather Service Des Moines IA
609 PM CDT TUE SEP 18 2018
IAZ081-082-092-093-190030-
Adams IA-Ringgold IA-Union IA-Taylor IA-
609 PM CDT TUE SEP 18 2018
...Area of Strong Thunderstorms Moving into Southwest Iowa...
At 608 PM CDT, Doppler radar was tracking an area of strong
thunderstorms 7 miles northwest of Clarinda, or 22 miles southwest
of Corning, moving east southeast at 35 mph.
Half inch hail and wind gusts up to 50 mph will be possible with
these storms. Rainfall amounts up to one inch will be possible with
these storms.
Locations impacted include...
Mount Ayr, Corning, Bedford, Lenox, Sun Valley Lake, Lake Icaria, New
Market, Clearfield, Diagonal, Kellerton, Prescott, Blockton, Gravity,
Tingley, Nodaway, Cromwell, Arispe, Sharpsburg, Redding and Shannon
City.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 4058 9492 4073 9491 4073 9493 4112 9493
4096 9403 4057 9403 4057 9456
TIME...MOT...LOC 2308Z 290DEG 32KT 4083 9511
REVPRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DES MOINES IA
937 PM CDT TUE SEP 18 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0430 PM HEAVY RAIN GARNER 43.10N 93.61W
09/18/2018 M3.25 INCH HANCOCK IA PUBLIC
RAINFALL TOTAL ENDING THIS MORNING
9/18/2018.
0300 PM TSTM WND GST 2 SSE ADAIR 41.47N 94.62W
09/18/2018 E60 MPH ADAIR IA DEPT OF HIGHWAYS
WINDS ESTIMATED AT OR ABOVE 60 MPH. HAIL A
BIT LARGER THAN PEAS.
0250 PM TSTM WND GST 4 NNE ANITA 41.50N 94.73W
09/18/2018 M60 MPH CASS IA MESONET
IDOT RWIS SITE ALONG I-80 WEST OF ADAIR.
0100 PM TSTM WND DMG OTTUMWA 41.02N 92.42W
09/18/2018 WAPELLO IA PUBLIC
DELAYED REPORT, TIME ESTIMATED BY RADAR -
TREE DOWN ON CAMPER, ROOF BUCKLED - VIA
SOCIAL MEDIA.
1120 AM TSTM WND DMG 1 SSW DES MOINES 41.56N 93.63W
09/18/2018 POLK IA PUBLIC
DELAYED REPORT, TIME ESTIMATED BY RADAR -
TREE DOWN AT LINCOLN HIGH SCHOOL - VIA
SOCIAL MEDIA.
1055 AM HAIL KELLOGG 41.72N 92.91W
09/18/2018 E1.00 INCH JASPER IA TRAINED SPOTTER
1044 AM HAIL 5 WNW VALERIA 41.75N 93.41W
09/18/2018 E0.75 INCH POLK IA PUBLIC
BRIEF PENNY SIZED HAIL 3 NE OF BONDURANT.
VIA SOCIAL MEDIA.
1030 AM HEAVY RAIN 3 NE KLEMME 43.03N 93.56W
09/18/2018 M3.19 INCH HANCOCK IA PUBLIC
MEASURED AT HOME WEATHER STATION.
1009 AM HEAVY RAIN 5 SSW VENTURA 43.06N 93.49W
09/18/2018 M4.00 INCH CERRO GORDO IA TRAINED SPOTTER
SPOTTER REPORTED 4 INCHES OF RAIN IN 2
HOURS.
&&The Des Moines radar (KDMX), 114 km away, was scanning. The volume nearest the first event began at 04:59 UTC.
39 heavy rain, 4 flood, 1 flash flood. Local standard time, as filed.
Local media relayed public report of heavy rainfall of 3.28 inches over the last 24 hours and still raining.
CoCoRaHS observer recorded heavy rainfall of 4.28 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.40 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 4.21 inches over the last 24 hours.
Estherville Municipal Airport ASOS recorded heavy rainfall of 3.93 inches over the last 24 hours.
Mason City Municipal Airport recorded heavy rainfall of 3.47 inches over the last 24 hours.
Public reported heavy rainfall of 3.25 inches and still raining as of time of the report.
Coop observer recorded heavy rainfall of 3.32 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.10 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.45 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.17 inches over the last 24 hours.
Mason City Municipal Airport ASOS recorded heavy rainfall of 3.47 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 4.52 inches over the last 24 hours.
Estherville Municipal Airport ASOS recorded heavy rainfall of 3.93 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 3.77 inches over the last 24 hours.
Hampton Municipal Airport AWOS recorded heavy rainfall of 3.64 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 3.17 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 4.21 inches over the last 24 hours.
Forest City Municipal Airport AWOS recorded heavy rainfall of 3.86 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.63 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.25 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 3.25 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.25 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 3.25 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 4.28 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.65 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 4.32 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.73 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.65 inches over the last 24 hours.
Emergency manager reported heavy rainfall of 4.90 inches over the last 24 hours. Impacts included several county roads closed due to overland flooding and water in the basements of homes and businesses in Kossuth County.
Coop observer recorded heavy rainfall of 3.68 inches over the last 24 hours.
Public reported heavy rainfall of 5.30 inches over the last 24 hours.
Trained spotter reported heavy rainfall of 2.69 inches.
Mesonet station recorded heavy rainfall of 3.26 inches over the last 24 hours.
Mesonet station recorded heavy rainfall of 3.15 inches over the last 24 hours.
Mesonet station recorded heavy rainfall of 3.89 inches over the last 24 hours.
Mesonet station recorded heavy rainfall of 3.88 inches over the last 24 hours.
Mesonet station recorded heavy rainfall of 3.54 inches over the last 24 hours.
Public reported heavy rainfall of 5.5 inches over the past 12 hours and 9.3 inches over the last 48 hours. They also reported basement flooding within their house.
Franklin County Sheriff's Office reported a number of roads across the county with water running over them, including a few impassable at the time of the call.
Law enforcement reported flooding in portions of the county with some roads impassible. Many roads have standing water and larger creeks and streams are rising out of their banks.
Law enforcement reported flooding in portions of the county with some roads impassible. Many roads have standing water and larger creeks and streams are rising out of their banks.
Law enforcement reported some roads closed in rural areas due to water over the road from several rounds of heavy rainfall. Rises also noted local creeks and streams and some overland flooding.
Law enforcement reported some roads closed in rural areas due to water over the road from several rounds of heavy rainfall. Rises also noted local creeks and streams and some overland flooding.
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, September 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: 781196, 781199, 781201, 781202, 781203, 781204, 781195, 781208, 781209, 781294, 781295, 781296, 781297, 781298, 781299, 781300, 781301, 781302, 781303, 781304, 781305, 781306, 781308, 781309, 781310, 781311, 781312, 781313, 781314, 781317, 781318, 781320, 781323, 781325, 781326, 781340, 781342, 781371, 781315, 781198, and more.