By Meteorologist Ashton Altieri

DENVER (CBS4) – For most of this week, summer monsoon moisture has been trapped on Colorado’s Western Slope. That changes through the weekend as the moisture surges east over the mountains and eventually onto the Front Range.

Anticipating a deluge of rain in some areas, the National Weather Service has already issued a Flash Flood Watch through Saturday evening for most of the mountains, all of the foothills, and the entire Denver metro area plus Boulder, Fort Collins, and Greeley. The watch may also be expanded into in Sunday as well.

READ MORE: Robert Killis, CSU Pueblo Student Arrested After Detectives Find Large Cache Of Weapons, Ammunition In Vehicle, Apartment

(source: CBS)

Thunderstorms will initially develop by early afternoon Friday and will slowly move east and northeast through the evening. The biggest threat for flash flooding is over the burn scars including the Cameron Peak, East Troublesome, WIlliams Fork, and Calwood burn areas. All of these scars have an “elevated” threat for flash flooding and mud slides.

(source: CBS)

Farther west, the Grizzly Creek burn scar near Glenwood Springs also has an elevated threat for additional flooding and mudslides. More closures along the  I-70 corridor through Glenwood Canyon are possible through the weekend and travelers should be prepared for major delays.

Computer weather models are suggesting some mountain areas will get up to 2 inches or more of rain through the weekend with rainfall rates reaching up to 1 inch per hour.

READ MORE: 5280 Trail Would Connect Neighborhoods In Denver's Downtown Core

(source: CBS)

The threat for heavy rain is somewhat less certain for the Denver, Boulder, and Fort Collins areas but the chance for rain is still relatively high from Friday night into Sunday.

It’s a different story on the Eastern Plains because of a sharp cut-off of moisture that will occur east of the urban corridor. Some areas in far northeast Colorado such as Julesburg, Wray, and Holyoke may not get any rain whatsoever.

Most of Colorado will also experience noticeably cooler temperatures on Saturday and Sunday. The Denver metro area will experience the coolest weather in weeks with high temperatures near 80 degrees over the weekend.

MORE NEWS: 'In Colorado, We Are Ready': Gov. Jared Polis Reacts To FDA Approval Of Pfizer COVID Vaccine Boosters

Meteorologist Ashton Altieri