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Heavy rain possible Wednesday, Thursday in western Colorado and Glenwood Canyon

CDOT says rain could "exceed thresholds over the burn scar"
glenwood canyon blue gulch lights i-70
Posted at 6:27 AM, Aug 18, 2021

DENVER – The National Weather Service and Colorado Department of Transportation are already warning of heavy rainfall in western Colorado this week that could again lead to flash flooding in Glenwood Canyon and other areas nearby.

For Tuesday, there is only a slight chance of a flash flood watch being issued, CDOT said in a daily release discussing the Glenwood Canyon project. But forecasts show the chance of heavy rain moving into the Western Slope Wednesday through Thursday.

“Any thunderstorms will be capable of moderate to heavy rainfall, and likely exceed thresholds over the burn scar,” CDOT said. “With a little luck, cloud cover and cooler temperatures could limit thunderstorm coverage, leading to more showery precipitation and lighter rates. However, current model trends this morning indicate a high risk for excessive rainfall across the area.”

After CDOT opened I-70 through Glenwood Canyon on Saturday morning, it was briefly shut down Sunday evening as a shower moved through the area, though no flash flooding occurred.

A flash flood watch was in effect for a little more than 2 hours Monday evening, but only light rain fell in the area. CDOT closed down one lane of traffic on eastbound I-70 as a precaution in case a full closure was necessary, but it was not, said department spokesperson Stacia Sellers.

The National Weather Service’s Grand Junction office wrote in its forecast discussion Tuesday morning that current models show the possibility of heavy rainfall and large hail with Wednesday’s storms in the forecast area. Flash flooding risk, particularly at burn scars like the one in Glenwood Canyon, will depend on how quickly the storms move and how much water they contain.

“Wednesday is shaping up to be an interesting day,” NWS forecasters wrote. “…Wednesday night into Thursday morning is shaping up to potentially be the wettest period of the forecast in the vicinity of the CO/UT border.”

Thursday is also expected to bring heavy rain and storms to western Colorado, though temperatures are expected to be much cooler – reaching highs in the 70s. Models are currently showing a widespread half-inch to inch of rain, according to the NWS.

CDOT said crews were able to haul 205 loads of debris out of the canyon on Monday on both ends. They hope to have the debris cleared from the Ty Gulch drainage by the end of Tuesday.

Crews will also Tuesday put in sensors near Blue Gulch and Devil’s Hole that can record any movement of the highway structure and are working on the request for proposal set to open to contractors on Thursday.

CDOT said if they have to close the highway through the canyon during the storms the next two days, they will put up the alternate routes on digital billboards and send out messaging through social media if they think it will be a long closure.

Aside from the threat to the Grizzly Creek burn scar and Glenwood Canyon, and other burn scars in western Colorado, the precipitation will continue to help the persistent drought that has been ongoing for months in the western half of the state.

Twenty percent of Colorado – all on the Western Slope – remains in extreme drought conditions, and most of the western half of the state is still experiencing some drought. But that is also a 10% drop in extreme or worse drought conditions since early May.