Red Rocks Hail Event 6/21

Summary: Quarter to golfball sized hail hit Red Rocks Amphitheatre around 9:30pm on 6/21. Authorities are reporting about 100 injuries. The atmosphere was primed. All major atmospheric ingredients were in place for severe thunderstorms with large hail, flash flooding, and tornadoes. The forecast timeline was 4pm to 10pm. A Severe Thunderstorm Watch was in effect. The Storm Predication Center (SPC) issued an “Enhanced Severe Weather Outlook” for Denver, Front Range, and Eastern Plains. This is a serious issuance. Dewpoints were in the low 60s (measure of moisture in the atmosphere), which is high for Denver especially in June. Outflow boundaries were widespread all night.

Source of image is unknown.

Image from Ylan Milton.

Meteorology

Below is the radar summary between 9pm and 9:50pm.

Here’s a static image at about 9:30pm. This is a severe thunderstorm with a significant hail column.

Below is the hail core that rolled right across Red Rocks Amphitheatre. It originated with a severe thunderstorm in the Foothills then dropped down in elevation across Lakewood and moved east into Denver. The orange represents the core of largest hailstones ranging from quarter to golfball sized.

Risk

Outdoor venues always have risk from severe weather. We see it during golf tournaments, and organized running/biking events especially in mountainous terrain (like Pikes Peak Ascent/Marathon, Leadville 100 events, Devil on the Divide, etc). You might recall the ‘DC 50mile Ultra” in Utah back in October 2021 when a foot of snow hit racers. A reported 87 racers were helped off the course.

I regularly work for Race Directors of these events providing a forecast and observe day-of weather. Most of the time nothing happens – the radar is clean and clear. But, occasionally, especially with afternoon/evening events, the weather can increase risk.

The key question is this: Do you have a plan?

4 thoughts on “Red Rocks Hail Event 6/21”

  1. Kristin Z

    A most excellent summary. Not only do the venues and organizers need a plan, but so do the individuals. Science, reasoning, and common sense aren’t always the popular and sexy choice, but they sure do mitigate a lot of suboptimal experiences. 🙂 thanks for all you do! I sure do love a good post mortem analysis so keep them coming and dive even deeper. 🙂

  2. Paul A Gallaher

    I would not consider going to do a lengthy outside activity without checking a comprehensive hourly forecast and the radar. Yesterday during our 37 mile bike ride in Summit County, I stopped and checked the weather radar to make a decision to plan the rest of our afternoon. My background as a pilot and a sailor has made me skeptical of forecasts and weather radar plots more than 2 hours old.
    😛

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