Time: 932 AM Thu June 18, 2020 Forecaster: Brad Simmons

Heavy Precipitation Outlook
Flash Flood Prediction Program

UNSEASONABLY COOL TROUGH OF LOW PRESSURE TO IMPACT THE DISTRICT THROUGH FRIDAY
-A relatively cold late season trough of low pressure will be impacting the District later today through Friday producing much needed rainfall along with thunderstorm activity at times. Temperatures today will be much cooler with highs in the 70's over the plains with 60's in the Front Range foothills. Normal high for Denver today is 83 degrees.
-Showers and thunderstorms will develop over the mountains and foothills between noon and 2pm. After 2 or 3pm showers will begin to move onto the plains with possibly a thunderstorm or two. Shower and isolated thunderstorm activity will continue likely through about midnight. Best chances for thunderstorms will be over the foothills. After midnight additional light rain showers will continue possible into Friday morning.
-Due to limited surface moisture thunderstorms today are expected to be weak to moderate and precipitation overall may favor general rain showers versus thunderstorms with the cooler temperatures over the plains. Total precipitation amounts from this afternoon through Friday morning expected to range from 0.2-0.6" with isolated higher amounts if a thunderstorm is observed.
STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.20" in 30-60 minutes. Weak to moderate thunderstorms will have the potential to produce rainfall rates of 0.1-0.4" in 10-30 minutes.

WORST CASE SCENARIO: A strong thunderstorm is able to develop and anchor in or near the foothills resulting in the potential for moderate to heavy rainfall of 0.3-0.9" in 15-45 minutes.

A LOOK AHEAD: Continued cool on Friday with highs in the upper 60's to lower 70's over the plains. Intermittent rain showers are expected through the day with possibly a thunderstorm in the afternoon. An additional 0.5-1.0" of rain is expected most areas Friday morning through midnight Friday with isolated higher and lower amounts. After midnight Friday conditions are expected to dry out.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 300 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Arapahoe 300 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Broomfield 300 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Denver 300 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Boulder 200 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Douglas 200 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Jefferson 200 PM TO 1000 AM FRI
Trace (100%) to 0.2" (75%) to 0.4" (20%) NONE
Foothills above 6500ft      
Boulder 100 PM TO 1000 AM FRI
Trace (100%) to 0.2" (80%) to 0.4" (35%) LOW
Douglas 100 PM TO 1000 AM FRI
Trace (100%) to 0.2" (80%) to 0.4" (35%) LOW
Jefferson 100 PM TO 1000 AM FRI
Trace (100%) to 0.2" (80%) to 0.4" (35%) LOW
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.