Time: 928 AM Thu July 23, 2020 Forecaster: Brad Simmons

Heavy Precipitation Outlook
Flash Flood Prediction Program

ISOLATED TO WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS
-Temperatures will remain rather warm today with highs reaching the lower 90's over the plains with upper 70's and 80's in the Front Range foothills. SSW flow aloft is transporting moisture into the area in the upper levels of the atmosphere and will help to produce widely scattered thunderstorms over the District this afternoon and early evening.
-Surface moisture is only modest resulting the storms that develop today producing mainly light to brief moderate rain, but an isolated brief heavy rain shower cannot be ruled out. Best chances for storms today will be from 3-9pm over the plains. Storms will move from SW to NE at 15-20mph.
-After 9pm this evening the majority of the shower and thunderstorm activity is expected to be coming to an end with a slight chance to experience an isolated rain shower overnight as moisture will be on the increase at the surface and aloft.
STORM RAINFALL POTENTIAL AND DURATION: Typical weak to moderate thunderstorms will produce a trace to 0.3". Stronger thunderstorms will have the potential to produce 0.3-0.6" in 10-30 minutes.

WORST CASE SCENARIO: A slow moving gust front induced thunderstorm may be able to tap into higher moisture with the potential to produce up to 1.0" of rain in 45-60 minutes.

A LOOK AHEAD: A monsoon moisture plume is expected to pass directly overhead on Friday resulting in widespread to numerous showers and thunderstorms in the afternoon and evening. Thunderstorms will be very capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 300 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Arapahoe 300 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Boulder 300 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Broomfield 300 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Denver 300 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Douglas 200 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Jefferson 200 PM TO 900 PM
Trace (80%) to 0.2" (30%) to 0.5" (10%) LOW
Foothills above 6500ft      
Boulder 100 PM TO 900 PM
Trace (90%) to 0.2" (40%) to 0.5" (10%) LOW
Douglas 100 PM TO 900 PM
Trace (90%) to 0.2" (40%) to 0.5" (10%) LOW
Jefferson 100 PM TO 900 PM
Trace (90%) to 0.2" (40%) to 0.5" (10%) LOW
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.