The National Weather Service issued a flood watch Monday to go into effect between Tuesday morning and Tuesday evening, Aug. 26. 

The watch affects Pitkin, Eagle, and Garfield counties, as well as much of western and southwestern Colorado. Between Tuesday and Thursday morning, the mountains around Aspen could see as much as an inch of rain, according to National Weather Service Meteorologist David Byers.

Byers expects the Aspen area to see around a 3/4-inch of rain, and downvalley to see a 1/2-inch. There could be periods of heavy rain that would accumulate a 1/2-inch or inch of rain in as little as an hour, which would warrant the National Weather Service to change the alert from a flood watch to a flood warning, Byers said.

“It’s not necessarily going to be a continuous light rain that builds up,” Byers said.

Should the agency issue a flood warning, he advised the public to know their evacuation routes, as flash floods can occur in minutes.

“Know where to go and what to do,” he said. “Move to higher grounds.”

Wildfire burn scars increase the risk of flash floods during weather events, as burnt soil becomes hydrophobic. 

“If you just pour a bottle of water on the soil, it won’t soak in at all. It runs off,” Byers said. “It beads up like it’s falling on an oil surface and just runs off, which makes it very hazardous for heavy rains.”

As little as a 1/4-inch of rain in 15 minutes on a fire scar can cause a major flood, according to Byers. 

The Roaring Fork Valley already saw heavy rains Monday, Aug. 25, before the National Weather Service issued a flood watch alert. On Monday morning, an estimated 0.54 inches of rain in the area caused several rock slides in Snowmass Canyon and on Colorado Highway 133, according to a Pitkin Alert. The county asked drivers to consider alternate routes and to drive safely.

Statistics company FindEnergy also reported at 9:52 a.m. Monday that 1,113 Pitkin County homes and businesses lost power. They regained electricity by Monday afternoon.