SPM 05-15-2018: Impressive Hail Accompanies Thunderstorms on Monday

Issue Date: Tuesday, May 15, 2018
Issue Time: 10:15AM MDT


Quite an exciting start to the week for the Urban Corridor on Monday. Early morning clearing helped initiate thunderstorms along the Front Range just before 11am. The first storm moved into Denver by 11am and brought with it quite the show! Due to the low freezing levels, hail almost immediately started falling out of the core of the storm. Penny sized hail covered the ground in what looked like a layer of snow over most of the metro area and downtown Denver. This caused some minor flooding along ungagged streams, but no flooding was reported. Below is the gage from Cherry Creek, which spiked after the rainfall just under the Action stage. The UDFCD gage network max 1-hour rainfall recorded was 0.94 inches (Watkins) with up to 0.8 inches in the urban areas. Further south in Parker, a storm dropped 3 inches of penny-sized hail that completely covered the roadways near the Pinery. It was enough accumulation that they brought in plows to clear the roads! Hope those folks didn’t change out their snow tires just yet.

The storms continued to move to the east over the Palmer Ridge and Northeast Plains into better storm dynamics. As expected, they quickly became severe and formed a bow. A bow echo is associated with strong winds and, sure enough, a gust of 75mph was recorded in Cheyenne County. Two storm chasers reported 2.75 inch hail (baseball) in Kit Carson County, which unfortunately blew out one of their windshield. Thankfully no one was hurt. 1-hour max rainfall was estimated at 1.5 inches. A CoCoRaHS gage north of Cheyenne Wells recorded 1.35 inches. Upslope flow continued to trigger less severe thunderstorms overnight giving the Southeast Plains some much needed rainfall. Radar estimates in this area were just over 0.5 inches.

Even with large amount of hail and heavy rainfall, no flooding was reported yesterday. To see rainfall estimates in your neighborhood, scroll down to the 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 accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.