Severe storms developed on September 20th.
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 OAX wrote it up.
Severe storms developed 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 Omaha, NE wrote its last area forecast discussion before the first event at Sep 20, 1:51 PM CST, 3 hours 17 minutes earlier.
Area Forecast Discussion National Weather Service Omaha/Valley NE 251 PM CDT Thu Sep 20 2018 .SHORT TERM...(Tonight through Sunday) Issued at 251 PM CDT Thu Sep 20 2018 At 2 PM, mesoanalysis placed a deepening surface low north of Sioux City with a cold front trailing southwest into central NE, between Ord and Albion. Thus far, the majority of thunderstorm activity has been post-frontal in nature. However, visible satellite data indicate a deepening cumulus field from near Wayne southwestward to west and southwest of Columbus, and a broken band of thunderstorms expected to materialize along that corridor in the next hour. The 18z Omaha sounding revealed the presence of a hot and moist boundary layer surmounted by steep mid-level lapse rates. However, a warm nose located around 350 mb was limiting MLCAPE values to less than 1000 J/kg. Weak cooling aloft associated with the arrival of a vigorous short-wave trough into the northern Plains will support further air mass destabilization this afternoon. When coupled with relatively strong, deep-layer southwesterly winds, the setup will favor organized squall line development with embedded bows and lewps capable of damaging winds. The the squall line is expected to move through far southeast NE and southwest IA by midnight with winds shifting to northwest with the frontal passage. High pressure will build into the mid MO Valley Friday and Friday night with highs in the 60s and lows dipping into the upper 30s to mid 40s. This weekend, a lee cyclone is forecast to develop over the northern High Plains before shifting east into SD. Winds will again strengthen from the south, drawing a warmer air mass back into the central Plains. .LONG TERM...(Sunday night through Thursday) Issued at 251 PM CDT Thu Sep 20 2018 The next strong short-wave trough is forecast to traverse the north-central U.S. on Monday into Monday night while an associated surface cold front surges southeast through the mid MO Valley. That front will be accompanied by showers and thunderstorms, similar to today. Highs in the 70s on Monday will fall back into the 60s and lower 70s by Tuesday as a cooler, continental air mass overspreads the region from the north. Temperatures may rebound slightly on Wednesday ahead of a strong cold front which is forecast to push through the mid MO Valley on Thursday. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 136 PM CDT Thu Sep 20 2018 Strong south winds ahead of a cold front today 16 to 26kts gusting 30 to 38kts. Thunderstorms will develop at KOFK around 20Z...spreading southeast toward KOMA/KLNK 23-03Z. MVFR cigs/vsbys with the storms along with gusty winds. Southwest winds becoming northwest. Gusty northwest winds Friday 15-30kts. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && SHORT TERM...Mead LONG TERM...Mead AVIATION...Zapotocny
Hazardous Weather Outlook National Weather Service Omaha/Valley NE 333 PM CDT Thu Sep 20 2018 IAZ043-055-056-069-079-080-090-091-NEZ015-018-032>034-042>045- 050>053-065>068-078-088>093-211045- Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont- Page-Thurston-Wayne-Stanton-Cuming-Burt-Platte-Colfax-Dodge- Washington-Butler-Saunders-Douglas-Sarpy-Seward-Lancaster-Cass- Otoe-Saline-Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson- 333 PM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of southwest Iowa...west central Iowa...east central Nebraska...northeast Nebraska and southeast Nebraska. .DAY ONE...Tonight and Friday A band of strong to severe thunderstorms is expected to spread east across the area this afternoon through this evening, along and ahead of a cold front. The primary hazard with these storms is damaging winds, though some hail is also possible. Minor flooding will continue along the Missouri River upstream of Lewis and Clark Lake in Knox County and in the vicinity of Brownville. .DAYS TWO THROUGH SEVEN...Friday night through Thursday Minor flooding will continue along the Missouri River upstream of Lewis and Clark Lake in Knox County. Minor flooding along the Missouri River in the vicinity of Brownville should subside by Friday. .SPOTTER INFORMATION STATEMENT... Storm spotter activation may be needed on a localized basis late this afternoon and this evening. NEZ011-012-016-017-030-031-211045- Knox-Cedar-Antelope-Pierce-Boone-Madison- 333 PM CDT Thu Sep 20 2018 This Hazardous Weather Outlook is for portions of northeast Nebraska. .DAY ONE...Tonight and Friday Isolated strong storms are possible this afternoon into early evening. Gusty winds and some small hail are possible. Minor flooding will continue along the Missouri River upstream of Lewis and Clark Lake in Knox County and in the vicinity of Brownville. .DAYS TWO THROUGH SEVEN...Friday night through Thursday Minor flooding will continue along the Missouri River upstream of Lewis and Clark Lake in Knox County. .SPOTTER INFORMATION STATEMENT... Storm spotter activation will not be required through Friday.
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
513 PM CDT THU SEP 20 2018
IAZ043-055-NEZ034-202300-
Monona IA-Harrison IA-Burt NE-
513 PM CDT THU SEP 20 2018
...SIGNIFICANT WEATHER ADVISORY FOR MONONA...NORTHWESTERN HARRISON
AND EASTERN BURT COUNTIES UNTIL 600 PM CDT...
At 512 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Onawa to 3 miles southeast of Craig.
Movement was northeast at 45 mph.
Half inch hail and wind gusts up to 50 mph will be possible with
these storms.
Locations impacted include...
Onawa, Tekamah, Mondamin, Ute, Pisgah, Moorhead, Mapleton, Blencoe,
Magnolia, Soldier, Little Sioux, Castana, Turin, Rodney, Pelican
Point State Recreation Area, Preparation Canyon State Park, Little
Sioux Scout Ranch, Summit Lake State Recreation Area and Kennebec.
A Severe Thunderstorm Watch remains in effect until 1100 PM CDT for
southwestern and west central Iowa...and east central Nebraska.
LAT...LON 4169 9584 4170 9639 4219 9604 4221 9595
4221 9567 4197 9567
TIME...MOT...LOC 2212Z 240DEG 38KT 4200 9609 4174 9631
ZAPOTOCNYPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
518 PM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0510 PM TSTM WND GST 2 ESE TEKAMAH 41.76N 96.18W
09/20/2018 M67 MPH BURT NE ASOS
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
556 PM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0521 PM TSTM WND GST BLAIR 41.54N 96.14W
09/20/2018 E65 MPH WASHINGTON NE TRAINED SPOTTER
ESTIMATED 60-65MPH WIND.
&&Special Weather Statement
National Weather Service Omaha/Valley Nebraska
558 PM CDT THU SEP 20 2018
NEZ065-202330-
Seward NE-
558 PM CDT THU SEP 20 2018
...SIGNIFICANT WEATHER ADVISORY FOR SEWARD COUNTY UNTIL 630 PM CDT...
At 558 PM CDT, Doppler radar was tracking a strong thunderstorm near
Beaver Crossing, or 15 miles southeast of York, moving northeast at
40 mph.
Nickel size hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Seward, Milford, Beaver Crossing, Goehner, Cordova and Tamora.
A Severe Thunderstorm Watch remains in effect until 1100 PM CDT for
southeastern Nebraska.
LAT...LON 4086 9737 4100 9711 4077 9692 4070 9726
4070 9737
TIME...MOT...LOC 2258Z 236DEG 36KT 4076 9734
MEADPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
607 PM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0605 PM HAIL 4 W BEAVER CROSSING 40.79N 97.35W
09/20/2018 M1.25 INCH SEWARD NE TRAINED SPOTTER
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
608 PM CDT THU SEP 20 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0605 PM TSTM WND GST 4 W BEAVER CROSSING 40.79N 97.35W
09/20/2018 E65 MPH SEWARD NE TRAINED SPOTTER
SMALL TREE LIMBS DOWN AND 65 MPH WIND
ESTIMATED.
&&The Omaha radar (KOAX), 60 km away, was scanning. The volume nearest the first event began at 23:06 UTC.
1 thunderstorm wind. Local standard time, as filed.
Sustained winds of 50 mph were reported with a gust up to 65 mph. Small tree limbs were blown down.
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: 781151.