SPM 07-20-2020: Rain, Wind, and Hail Sweep Through the Northeast Plains

Issue Date: Monday, July 20th, 2020
Issue Time: 10:40AM MDT

Summary:

A group of severe thunderstorms swept through northeast Colorado yesterday, bringing heavy rain, strong winds, hail, and even a weak tornado in Phillips County. An impressive 1.83 inches of rain was reported by a CoCoRaHS observer just north of Sterling in northeastern Colorado, and a nearby CoAgMET gage also picked up 1.68 inches of rain, so QPE in this area appears to be underestimated. This heavy rainfall was associated with a large severe thunderstorm that dropped 1-inch hail and produced a 71 mph wind gust over the area. Some crop and power pole damage was reported from this gust near the town of Iliff.

The Palmer Ridge also picked up some decent rainfall as storms fired over the southern Front Range and tracked east. Several CoCoRaHS rain reports and ALERT gages exceeded 0.40 inches (up to 0.44”) over the southern Urban Corridor and Palmer Ridge. The QPE map indicates that storms may have dropped a little over an inch of rain over portions of Lincoln, Cheyenne, and Kiowa counties. One of these storms prompted a Flood Advisory from NWS Boulder over Lincoln County from 4-7 PM MDT.

Storms back over the high country produced more wind than rainfall. A 58 mph gust was picked up at a Basalt mesonet site, and QPE was estimated around 0.25 inches for storms near the area. A storm tracked over the Decker burn scar, which prompted a Flash Flood Warning as radar indicated over 0.3” of rain had fallen. NWS ASOS stations near the area only picked up to 0.07” of rain, so this storm was very isolated over the higher terrain. Additionally, radar-derived QPE likely under-estimated sub-cloud evaporation. As of this morning, no flooding was reported.

For 24-hour to 72-hour rainfall estimates in your area, check out our State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The 24-hour, 48-hour and 72-hour total precipitation contain bias corrections that are not disaggregated into the hourly estimates, so there will likely be some differences. The accumulation ending time is 7AM of the date shown in the bottom right corner. Also shown optionally are vulnerable fire burn areas (post 2012), which are updated throughout the season to include new, vulnerable burn areas. The home button in the top left corner resets the map to the original zoom.