Old Market Flood Summary

River Graphs

The images below are graphs of several river locations in and around the Omaha metro. They depict how fast the rivers rose throughout this event. On Papillion Creek the water rose 10 feet or more in 15 minutes!  Also included below are river graphs along the Missouri River where a 1.5 to 2 foot rise was recorded.

Papillion Creek Watershed Hydrographs

Big Papillion at Fort Street	Big Papillion at Pacific Street	Big Papillion at Q Street
Little Papillion near Irvington	Cole Creek at Blondo Street	Little Papillion Creek at Ak-Sar-Ben
West Papio @ Millard Avenue	Papillion Creek at Fort Crook	Papillion Creek near La Platte

Missouri River Hydrographs

Missouri River at Omaha	Missouri River at Highway 92	Missouri River at Plattsmouth

Summary of NWS Services and Warnings during the event

In response to the heavy rain throughout the area, the NWS office in Omaha issued several flood warnings.

Initial Flash Flood Warning - issued at 9:05 pm. This warning was issued over a fairly large area due to the west-east orientation and slow movement of the storms.	Updated Flash Flood Warning - issued at 9:35 pm. This updated warning included information about the increasing severity of the flooding, specifically mentioning the life-threatening situation that was unfolding.	Updated Flash Flood Warning - issued at 10:32 pm. This update was issued to declare a flash flood emergency for downtown Omaha and Council Bluffs.

The National Weather Service Office in Omaha issued three flood advisories and four flash flood warnings. The first flood advisory for downtown Omaha was issued at 8:39 pm. The first flash flood warning for Omaha was issued at 9:05 pm. The heavy rain started around 10 pm. The first report of street flooding was around 9:10 pm with the first report of a vehicle being stranded around 9:20 pm.

Flooding Outlooks (Issued by the Weather Prediction Center)

The Excessive Rainfall Outlooks issued leading up to the event indicated a Marginal threat of excessive rainfall. A final outlook (bottom right) was issued at 0109 UTC on the 8th, about 40 minutes prior to the onset of heavy rain in Omaha.

Excessive Rainfall Outlook for August 7th Issued 8/5/2023	Excessive Rainfall Outlook for August 7th Issued 8/6/2023
Excessive Rainfall Outlook for August 7th Issued 8/7/2023	Excessive Rainfall Outlook for August 7th Issued 8/7/2023
The image above is the Mesoscale Precipitation issued at 9:06 pm on August 7th. The purpose of the discussion was to highlight the flash flood potential.  Click here for the full technical discussion.

Photos & Video

14th and Leavenworth (photo credit John Beck-Hoffman)	Jones Street (between 10th and 11th) (photo credit Jacob Buckingham)

Meteorological Data

Upper-air analysis - 7 pm August 7th

In both the 250 and 500-mb analyses, a shortwave trough was evident from the central Dakotas into eastern Colorado with the exit region of a 70 kt jet streak moving through the base of the trough over western Kansas. Those features were instrumental in providing sufficient lift in the atmosphere for the thunderstorms to develop. Even at 700 mb, the shortwave trough was evident with a downstream zone of very moist conditions (e.g., 700-mb dewpoints of 6 to 8 degrees Celsius) over central and eastern parts of Nebraska into northern Kansas. The 700-mb moisture axis was consistent with that observed at 925 mb where dewpoints of 18 to 22 degrees Celsius were being advected north into the mid-Missouri Valley along a southerly, 20 to 30 kt low-level jet. Furthermore, the low-level jet enhanced lift to the north of a differential-heating boundary situated across southeast Nebraska (discussed in the next section) to foster the thunderstorm development over eastern Nebraska.

250 mb Upper-Air Analysis	500 mb Upper-Air Analysis	700 mb Upper-Air Analysis	925 mb Upper-Air Analysis

Surface analysis

The moist conditions observed at 700 and 925 mb were also present at the surface with mid afternoon to early evening dewpoints commonly in the low to mid-70s over eastern Nebraska. Residual cloud-cover from early day showers and thunderstorms from south-central into east-central Nebraska held temperatures in the upper 70s to low 80s. In contrast, stronger diabatic heating occurred over northern Kansas into southeast Nebraska where temperatures warmed into the low to mid-90s. As a result, a differential-heating boundary became established by mid afternoon south of I-80 in southeast Nebraska. And as mentioned in the upper-air section, enhanced lift to the north of that boundary along the low-level jet was likely a contributor to the initial storm development near David City.

4 pm - August 7th	7 pm - August 7th

Mesoanalysis

4 pm - August 7th
Upwind propagation vectors depict an easterly expected track for any larger-scale convective system to flow across eastern Nebraska. The speed at which this system would propagate eastward slows down considerably between southeast Nebraska and areas just to the north, with slower movement closer to Omaha.	Strong moisture transport is focused through the eastern half of Kansas into southeast Nebraska before it runs into a west-to-east convergence zone located over east-central Nebraska. Focused moisture transport into a low-level frontal zone would signal increased chances for heavy rainfall.	Low-level moisture convergence is increasing across eastern Nebraska, just south of Omaha, as depicted by the red contours in the image above. Shaded values of precipitation potential placement are increasing in southeast Nebraska, indicating increased low-level moisture that could be realized in the form of heavy rain.

7 pm - August 7th
Storm-driving winds continue to be weak across far eastern Nebraska into Omaha, which coincides with increasing precipitable water. Any upscale growth in the convection would have the potential to not only move slowly but also train over areas for longer periods.	Moisture transport has increased in eastern Nebraska and continues to be pointed into a convergence zone located over eastern Nebraska and Omaha. Low-level moisture is actively being pooled and would increase instability, mid-level lapse rates and increase the potential for warm-rain processes to occur. The west-to-east orientation of the convergence would mean that storms that form in the convergence zone would travel along it for a prolonged period thanks to slow storm-driving winds.	Low-level moisture convergence has maximized over Omaha and points westward, allowing for easier storm development. At the same time, precipitation potential placement has increased in the Omaha area, indicating increasing low-level relative moisture and increasing precipitable water which makes warm-rain processes easier to occur. Once again, the west-to-east orientation of the convergence would mean that storms that form in the convergence zone would travel along it for a prolonged period thanks to slow storm-driving winds.

Weather Balloon Data from August 7th

Weather balloon data at 7 am revealed an environment already conducive for strong storms with steep midlevel lapse rates, abundant moisture (e.g., precipitable water values of 1.44"), and modest amounts of vertical wind shear. The one inhibiting factor was a capping inversion in the 900-700-mb layer. By 7 pm, additional atmospheric moistening (e.g., precipitable water increased to 1.61", the 90th percentile rank on a climatological basis) and daytime heating yielded a strongly unstable air mass, supportive strong updrafts, and downdrafts. Vertical shear was on the margins of that which support organized storm modes. However, the presence of the strong instability compensated, allowing for the development of a large, high-precipitation supercell that produced extreme rainfall rates in the Omaha metro.

7 am Sounding Analysis	7 pm Sounding Analysis

Radar and Satellite Data

Below are three satellite loops of the event: visible, infrared, and water vapor.

Visible August 7th - 4 pm to 8 pm	Infrared August 7th - 4 pm to 11 pm	Water Vapor August 7th - 4 pm to 11 pm

Multi-Radar/Multi-Sensor Data (MRMS) Data

The images below are radar-derived rainfall information. Additional information on the MRMS dataset can be found here.

This is an image of the 3-hour rainfall as depicted by the radar. The values shown here are underestimated when compared to actual reports.	This is an image of CREST Unit Streamflow. This parameter, blue and white pixels, shows the significant runoff that occurred due to the heavy rainfall.	This is an image of the radar-estimated rainfall compared to flash flood guidance (FFG). FFG is a computer-estimated value of how much rain it takes to cause flooding. Values above 1 indicate flooding could be happening.	This is an image of how often this type of rainfall occurs on average. Values exceeding 10 are high, especially for urban areas like the Omaha/Council Bluffs metro.

Flooding Reports

Rain Reports

Across the Omaha/Council Bluffs Metro, rainfall amounts of 3 to 5 inches were common, with several unofficial reports of 6 inches or more. Not only were the rainfall amounts substantial but even more interesting was the rainfall rate. The majority, and heaviest, rains fell over a short period of time, about one hour. As the two graphs below show, as much as four inches fell in one hour in some places, with higher amounts likely. Based on the NOAA Atlas 14 dataset, this translates to a rain event that happens, on average, once every 100 to 150 years!

Above is a rainfall map from the event. Note that Omaha was not the only area that received heavy rainfall. To the west, very heavy rain was also observed in Butler and Saunders counties, though the flooding was less severe.	Rainfall Report Summary
CoCoRaHS Reports (click to interact)	Precipitation Reports (zoomed)
As the two graphs below show, as much as four inches fell in one hour in some places, with higher amounts likely. Based on the NOAA Atlas 14 dataset, this translates to a rain event that happens, on average, once every 100 to 150 years. When looking at the rainfall amounts over half an hour it is possible some rainfall rates exceeded the 200-year event.
Rainfall graph at Ed Creighton Blvd	Rainfall graph at 20th and Pierce
Data Courtesy of the City of Omaha

Other Weather Reports

In addition to the flooding and heavy rain reports, there were numerous reports of hail and damaging winds.