An initially unimpressive thunderstorm complex over northeast Nebraska rapidly intensified during the morning of August 10, 2020. After a few sporadic early morning damage reports, the intensifying storms began to more readily produce damaging winds in excess of 50 kts around 1340Z.
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.
An initially unimpressive thunderstorm complex over northeast Nebraska rapidly intensified during the morning of August 10, 2020. After a few sporadic early morning damage reports, the intensifying storms began to more readily produce damaging winds in excess of 50 kts around 1340Z. Those damaging winds increased in coverage and intensity as the storms moved east into Iowa. The portion of the thunderstorm complex that moved through the NWS Omaha forecast area marked the approximate beginning of an intense derecho that tracked across portions of Iowa, Illinois, Wisconsin, Indiana, Michigan, and Ohio. Within the NWS Omaha forecast area, there were more than 20 local storm reports of wind damage and measured severe wind gusts, including more than 50,000 power outages.
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 Aug 10, 5:35 AM CST, 2 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Omaha/Valley NE 635 AM CDT Mon Aug 10 2020 ...Updated Aviation Forecast Discussion... .DISCUSSION... Issued at 210 AM CDT Mon Aug 10 2020 A surface cold front is currently draped across the area starting from northeast Colorado extending northeastward to to just east of Minneapolis, Minnesota. A nocturnal 850mb jet is oriented parallel to the cold front and becomes westerly as it reaches far eastern Nebraska/western Iowa. These two factors are combining to force some modest convection along NE/SD border, with more convection beginning to sprout up, extending westward into south-central South Dakota. The orientation of the low-level jet is providing some convergence along the front, but since it is oriented parallel to it, that convergence is not overly strong. Surface CIN values are lowest just ahead of the front at around 140 J/kg in far northeast Nebraska and increase along the front as you go southwestward. Surface based CAPE values associated with the CAPE minimum have slightly declined to around 3500 J/kg but still allow for strong convection to occur. The latest runs of the HRRR, ESRL HRRR, and RAP suggest that a cluster of storms may move eastward along with the zonal flow aloft, but if robust convection does get going a strong cold pool may allow for a more southeastward propagation to occur with the primary hazard being damaging wind gusts. As the today continues, the cold front is expected to march southeast and is expected to make its way to northwest Missouri by 00z Tuesday, and will bring cooler temperatures ranging from the upper 70's in the northwestern CWA to the mid to upper 80's in the far southeastern corner. Isolated to scattered showers and storms will be possible as the front passes through the area but with limited development in the model solutions, limited activity is expected. Looking beyond today's forecast, Tuesday is expected to be dry after any lingering precipitation from the frontal passage exits the area early in the morning. Highs in the mid to upper 80's are expected throughout eastern Nebraska as southeasterly surface flow returns. Global deterministic models are currently hinting at the possibility of a nocturnal MCS that could begin in western NE/SD and propagate ESE forming an MCV and bringing overnight and early morning rain chances to eastern Nebraska. This scenario is also depicted once again Wednesday evening/Thursday morning with the main difference being the propagation of the nocturnal MCS, with the GFS keeping it north of the area and the ECMWF passing it through southeastern Nebraska. Beginning Wednesday, mid-level ridging begins building over southern New Mexico and will slowly begin shifting the mid-level flow northwesterly. Beyond the Wednesday and Thursday nights' storm chances, the bulk of any activity is expected to stay more into Iowa as different shortwave impulses push through the mid- level flow. High temperatures are expected to stay in the upper 80's to around 90, with no real scorchers expected. Model solutions begin to diverge Sunday, with the ECMWF depicting a cold front to pass through the area, while the other global solutions depict a very limited response in surface temperatures and wind direction. If this front comes to fruition, we could enjoy another trip into the lower 80's for highs to start off next week. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 629 AM CDT Mon Aug 10 2020 Some lingering low stratus is beginning to be cleared out by convective outflow near the NE/SD border, and ceilings are expected to improve at KOFK within the next hour to VFR. This convection northwest of KOFK is associated with a cold front and should stay north of the TAF sites this morning but will likely kick out some strong wind gusts in KOFK's direction. Looking through the rest of the day, the cold front will continue marching southeastward with some gust conditions possible at KLNK and KOFK with gusts reaching around 21 kts or so. A few spotty showers and storms will be possible with the front, but they are expected to stay very sparse, keeping them out of the TAFs for all sites. Otherwise, VFR conditions are expected through the TAF period with a slightly gusty afternoon giving way to a rather calm night. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && DISCUSSION...Petersen AVIATION...Petersen
Hazardous Weather Outlook National Weather Service Omaha/Valley NE 434 AM CDT Mon Aug 10 2020 IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034- 042>045-050>053-065>068-078-088>093-102345- Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont- Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison- Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler- Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline- Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson- 434 AM CDT Mon Aug 10 2020 This Hazardous Weather Outlook is for portions of southwest Iowa...west central Iowa...east central Nebraska...northeast Nebraska and southeast Nebraska. .DAY ONE...Today and Tonight Isolated showers and storms are possible this morning and today as a cold front continues to move southeast through the area. The front is expected to reach far southeast Nebraska by 7pm and may stall out after the it crosses into northeast Kansas/northwest Missouri. While an isolated storm or two may become severe, widespread severe activity is not expected at this time. The best chance for any severe activity will be in far southeast Nebraska, extending into KS/MO. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Periodic showers and storms continue to be possible into this weekend. Severe storm potential is uncertain at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
651 AM CDT MON AUG 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0610 AM TSTM WND DMG NIOBRARA 42.76N 98.03W
08/10/2020 KNOX NE PUBLIC
PERSON REPORTED A LARGE TREE DOWN BY THE
MISSOURI RIVER NEAR NIOBRARA, NE. FROM
PICTURE, ~8 INCH DIAMETER TREE APPEARED TO
BE SNAPPED AT ITS BASE.
&&
DMPSpecial Weather Statement
National Weather Service Omaha/Valley Nebraska
803 AM CDT Mon Aug 10 2020
IAZ043-NEZ015-033-034-101330-
Monona IA-Thurston NE-Burt NE-Cuming NE-
803 AM CDT Mon Aug 10 2020
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN MONONA...NORTH
CENTRAL BURT...NORTHEASTERN CUMING AND THURSTON COUNTIES UNTIL 830 AM
CDT...
At 803 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Dakota City to near Pender. Movement was
east at 45 mph.
Wind gusts up to 55 mph will be possible with these storms.
Locations impacted include...
Walthill, Winnebago, Whiting, Decatur, Macy, Rosalie and Lewis And
Clark State Park.
This includes Interstate 29 between mile markers 115 and 125.
A Severe Thunderstorm Watch remains in effect until 1100 AM CDT for
west central Iowa...and northeastern and east central Nebraska.
LAT...LON 4227 9635 4226 9633 4223 9632 4222 9633
4221 9606 4193 9624 4208 9669 4228 9658
TIME...MOT...LOC 1303Z 287DEG 39KT 4243 9647 4208 9667
MEADSpecial Weather Statement
National Weather Service Omaha/Valley Nebraska
830 AM CDT Mon Aug 10 2020
IAZ043-055-NEZ015-034-101415-
Monona IA-Harrison IA-Thurston NE-Burt NE-
830 AM CDT Mon Aug 10 2020
...SIGNIFICANT WEATHER ADVISORY FOR MONONA...NORTHWESTERN HARRISON...
BURT AND SOUTHEASTERN THURSTON COUNTIES UNTIL 915 AM CDT...
At 828 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Hornick to near Craig. Movement was east
at 45 mph.
Wind gusts of 50 to 55 mph will be possible with these storms.
Locations impacted include...
Onawa, Tekamah, Lyons, Whiting, Decatur, Ute, Pisgah, Moorhead, Macy,
Woodbine, Oakland, Mapleton, Blencoe, Soldier, Little Sioux, Castana,
Turin, Rodney, Preparation Canyon State Park and Willow Lake
Recreation Area.
This includes Interstate 29 between mile markers 92 and 125.
A Severe Thunderstorm Watch remains in effect until 1100 AM CDT for
west central Iowa...and northeastern and east central Nebraska.
LAT...LON 4169 9572 4183 9656 4188 9656 4224 9633
4223 9633 4221 9567 4187 9567 4186 9563
TIME...MOT...LOC 1328Z 268DEG 46KT 4219 9615 4175 9642
MEADSpecial Weather Statement
National Weather Service Omaha/Valley Nebraska
842 AM CDT Mon Aug 10 2020
IAZ055-069-NEZ034-044-045-051>053-066-101415-
Pottawattamie IA-Harrison IA-Saunders NE-Sarpy NE-Burt NE-
Lancaster NE-Washington NE-Douglas NE-Dodge NE-
842 AM CDT Mon Aug 10 2020
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN POTTAWATTAMIE...
SOUTHWESTERN HARRISON...NORTHWESTERN SARPY...SOUTHEASTERN BURT...
WASHINGTON...NORTHEASTERN LANCASTER...SOUTHEASTERN DODGE...DOUGLAS
AND SAUNDERS COUNTIES UNTIL 915 AM CDT...
At 841 AM CDT, Doppler radar was tracking outflow from strong
thunderstorms along a line extending from 5 miles west of Mondamin
to 5 miles north of Valley to Weston. Movement was southeast at 50
mph.
Wind gusts up to 50 mph will be possible with the passage of the
gust front.
Locations impacted include...
Omaha, Blair, Wahoo, Gretna, Missouri Valley, Ashland, Valley, Logan,
Arlington, Yutan, Fort Calhoun, Waterloo, Mead, Mondamin, Kennard,
Weston, Modale, Elkhorn, Millard and Bennington.
This includes the following highways...
Interstate 29 between mile markers 71 and 89.
Interstate 80 in Nebraska near mile marker 446.
A Severe Thunderstorm Watch remains in effect until 1100 AM CDT for
east central Nebraska.
LAT...LON 4121 9607 4101 9644 4102 9646 4100 9646
4089 9667 4120 9689 4143 9639 4176 9616
4169 9574
TIME...MOT...LOC 1341Z 314DEG 54KT 4171 9612 4138 9633 4119 9674
MEADPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
856 AM CDT MON AUG 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0855 AM TSTM WND GST 1 WNW VALLEY 41.32N 96.37W
08/10/2020 M56 MPH DOUGLAS NE OFFICIAL NWS OBS
PEAK WIND GUST MEASURED AT OAX OFFICE.
&&
PFPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
857 AM CDT MON AUG 10 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0848 AM NON-TSTM WND GST 2 ESE TEKAMAH 41.77N 96.18W
08/10/2020 M61 MPH BURT NE ASOS
ASOS STATION KTQE TEKAMAH AIRPORT.
&&The Omaha radar (KOAX), 60 km away, was scanning. The volume nearest the first event began at 14:02 UTC.
5 thunderstorm wind. Local standard time, as filed.
Public reported a large tree snapped off which was approximately 3 feet in diameter.
Coop Observer estimated winds of 70 mph. Noted that several trees were down in his area.
Public personal weather station measured a wind gust of 50 kts.
Coop Observer called in with an estimated wind speed of 60 mph. Noted that several large trees were down in their area.
Harlan Airport AWOS measured a wind gust of 56 kts.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyWarnings in Iowa, August 2020
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: 915752, 915753, 915756, 915759, 915760.