Heavy rainfall continued across portions of central and northern Iowa through mid to late September. This allowed rivers across the area to go back into flood through the latter portion of the month.
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.
Heavy rainfall continued across portions of central and northern Iowa through mid to late September. This allowed rivers across the area to go back into flood through the latter portion of the month. The West Fork of the Des Moines River remained in flood at the end of September and will be included in the October StormData event as well. The basins impacted by flooding were the Des Moines, Cedar, Winnebago, Shell Rock, and Boone River basins as well as Black Hawk Creek at Hudson.
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 20, 5:45 AM CST, 2 hours 30 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 645 AM CDT Thu Sep 20 2018 .DISCUSSION.../Today through Wednesday/ Issued at 314 AM CDT Thu Sep 20 2018 Fairly quiet in the mid/long range with focus on today into tonight with severe weather chances and heavy rain chances still through the morning hours. Overall have a strengthening upper level trough moving through the intermountain west which is expected to lift east northeast through the region today into tonight. An associated surface low pressure is centered across SW NE/NW KS and ERN CO with a warm front stretching ENE through eastern NE and central/north central Iowa. Moisture transport ahead of this system has been oriented straight into NE Nebraska and northern IA through the overnight hours with ongoing shower and isolated thunderstorm activity in place across the northern third of the forecast area. Backbuilding continues on the south side of the rain area which is expected to continue through sunrise. However the entire area of rain is expected to slowly ooze northward through this morning as the warm front begins to lift north with the sfc low beginning to lift ENE into central NE by mid morning. WPC had a moderate risk of excessive rainfall across the north and that continues through 12z. Rain rates have settled down some in the past few hours, but continued fetch of moisture into the area and chances for heavy rain still possible as moisture transport to strengthen even further toward 12-15z. Therefore will continue the flash flood watch through this morning. Focus beyond early this morning, then shifts to the severe threat for thunderstorms toward mid/late afternoon into tonight. The sfc low off to the southwest to become situated near the Sioux City area by 18z and then lift into SW MN toward 21z before moving into NW WI by late evening. The associated warm front will continue to lift northward into southern MN by this afternoon, with a trailing cold front stretching from NW IA through central/eastern NE toward mid/late afternoon. Some question as to how far north the warm front will lift and expect development of storms along/south of the front toward mid/late afternoon. With the sfc low expected to be in NW IA/SW MN, could have a chance for some of the activity across far northern Iowa. These storms are expected to be more discrete and will bring the better chances for tornado development near the low pressure area and the aforementioned warm front. CAPE values around 2000 J/kg or higher expected in the warm sector with strong low level/deep layer shear in place. Some of the higher res models keep the sfc low a bit further south tracking closer to the IA/MN border which would increase the tornado threat across the far northern forecast area near the triple point. Storms also expected to develop along the sfc cold front extending S/SW from the sfc low through the late afternoon hours. As the front slides across the area this evening will see a continued chance for thunderstorms and severe wind gusts. If can get some bowing segments in the line and orientation of the 0-3 shear vector, could see some brief spinups along the line of storms as well in addition to the damaging wind threat. Enough instability and shear that could see some large hail with the storms later today/tonight as well, but best chances will be with the storms initially especially in any storms that remain discrete. The front should exit the area by late tonight with precip chances waning as well by Friday morning. Other issue besides the severe weather will be gusty winds ahead of the front across the forecast area today. Winds aloft to increase to around 30 to 40 kts with a tightening sfc pres gradient. Harder to get these winds to translate to the surface with mixing versus in a CAA pattern, but still should get breezy to windy conditions. Would not be surprised either if a few sites especially in the south/west today hit advisory criteria at times. However do not feel it will be widespread enough or consistent enough to issue a wind advisory for now. High pressure to then build into the area behind the system for Friday into Sunday with dry and cooler conditions. Another system to move through the region Monday into Tuesday bringing the next chances for rain and storms with another system toward late next week. More seasonable temperatures expected throughout the mid/long range with a stronger cooldown looking probable just beyond the forecast period. && .AVIATION.../For the 12Z TAFS through 12Z Friday morning/ Issued at 645 AM CDT Thu Sep 20 2018 Showers are expected to gradually diminish this morning across the northern Iowa as the area of rain is expected to lift into MN as a warm front lifts northward through the day. This should allow IFR to MVFR CIGS to lift into VFR range. Southerly to southeasterly winds will increase and become gusty through the day. Additional thunderstorms expected late this afternoon into tonight as a cold front moves through the area. Winds to shift to the west and become gusty behind the front with CIGS dropping into the MVFR and possibly IFR range overnight. && .DMX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 1 PM CDT this afternoon for IAZ004>007- 015>017-023>028. && DISCUSSION...Beerends AVIATION...Beerends
Hazardous Weather Outlook National Weather Service Des Moines IA 434 AM CDT Thu Sep 20 2018 IAZ004>007-015>017-211000- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- 434 AM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Severe thunderstorms are possible late this afternoon into this evening. The main severe threats are damaging winds and possibly a few tornadoes, large hail is a secondary threat. locally heavy rainfall is also possible. Gusty non-thunderstorm winds of 20 to 30 mph with gusts to 40 mph or more are expected today. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Intermittent thunderstorm chances return to the forecast Monday through much of next week. At this time the threat of severe weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is expected late this afternoon into this evening. IAZ023>028-033>039-211000- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk- 434 AM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Severe thunderstorms are possible late this afternoon into tonight. The main severe threats are damaging winds and possibly a few tornadoes, large hail is a secondary threat. locally heavy rainfall is also possible. Gusty non-thunderstorm winds of 20 to 30 mph with gusts to 40 mph or more are expected today. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Intermittent thunderstorm chances return to the forecast Monday through much of next week. At this time the threat of severe weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is expected late this afternoon into this evening. IAZ044>050-211000- Crawford-Carroll-Greene-Boone-Story-Marshall-Tama- 434 AM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong to severe thunderstorms are possible this evening into tonight. The main severe threats are damaging winds and possibly a tornado, large hail is a secondary threat. locally heavy rainfall is also possible. Gusty non-thunderstorm winds of 20 to 30 mph with gusts to 40 mph or more are expected today. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Intermittent thunderstorm chances return to the forecast Monday through much of next week. At this time the threat of severe weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed this evening into tonight. IAZ057>062-070>075-081>086-092>097-211000- Audubon-Guthrie-Dallas-Polk-Jasper-Poweshiek-Cass-Adair-Madison- Warren-Marion-Mahaska-Adams-Union-Clarke-Lucas-Monroe-Wapello- Taylor-Ringgold-Decatur-Wayne-Appanoose-Davis- 434 AM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight A strong to possibly severe thunderstorm will be possible this evening into tonight. The main severe threat will be damaging winds. An isolated tornado or large hail cannot be ruled out. Locally heavy rainfall is also possible. Gusty non-thunderstorm winds of 20 to 30 mph with gusts to 40 mph or more are expected today. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Intermittent thunderstorm chances return to the forecast Monday through much of next week. At this time the threat of severe weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed this evening into tonight. MJB
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
438 AM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0415 AM FLASH FLOOD HAMPTON 42.74N 93.20W
09/20/2018 FRANKLIN IA LAW ENFORCEMENT
FRANKLIN COUNTY SHERIFFS OFFICE REPORTED A
NUMBER OF ROADS ACROSS THE COUNTY WITH WATER
RUNNING OVER THEM, INCLUDING A FEW
IMPASSABLE AT THE TIME OF THE CALL.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
744 AM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0712 AM HEAVY RAIN HAMPTON 42.75N 93.20W
09/20/2018 E5.50 INCH FRANKLIN IA PUBLIC
5.5 INCHES OF RAIN IN THE PAST 12 HOURS. 9.3
INCHES OF RAIN IN THE PAST 48 HOURS.
BASEMENT FLOODING IN THE HOUSE. REPORT VIA
SOCIAL MEDIA.
&&
MJBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
840 AM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0839 AM HEAVY RAIN NEW HARTFORD 42.57N 92.62W
09/20/2018 E2.69 INCH BUTLER IA TRAINED SPOTTER
&&The national radar mosaic for the moment the first event began.
13 flood. Local standard time, as filed.
The Winnebago River at Mason City crested at 12.17 feet on 21 September 2018 at 0545 UTC.
The West Fork of the Des Moines River at Estherville crested twice through the period and remained in flood into October. The first crest was at 10.62 feet on 21 September 2018 at 2145 UTC, the second crest was at 9.81 feet on 29 September 2018 at 1915 UTC.
The Cedar River at Cedar Falls crested at 96.36 feet on 23 September 2018 at 1400 UTC.
The Shell Rock River at Shell Rock crested at 15.44 feet on 22 September 2018 at 1715 UTC.
The Des Moines River at Fort Dodge crested at 14.14 feet on 23 September 2018 at 1645 UTC.
The West Fork of the Des Moines River at Humboldt crested at 12.83 feet on 23 September 2018 at 0400 UTC.
The East Fork of the Des Moines River at Algona crested at 19.16 feet on 22 September 2018 at 1915 UTC.
Black Hawk Creek at Hudson crested at 14.28 feet on 22 September 2018 at 1100 UTC.
The Cedar River at Waterloo crested at 18.96 feet on 23 September 2018 at 1930 UTC.
The Iowa River at Rowan crested at 14.41 feet on 23 September 2018 at 0445 UTC.
The West Fork of the Des Moines River at Emmetsburg crested at 11.29 feet on 23 September 2018 at 0530 UTC.
The Des Moines River at Stratford crested at 23.08 feet on 24 September 2018 at 1245 UTC.
The Boone River at Webster City crested at 14.40 feet on 23 September 2018 at 1800 UTC.
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: 785689, 785683, 785681, 785695, 785686, 785687, 785679, 785688, 785680, 785694, 785682, 785696, 785697.