Time: 756 AM Mon September 20, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH A SLIGHT CHANCE FOR RAIN SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON, WITH RAIN SHOWERS THIS EVENING - A cold front moved through the region overnight effectively dropping our high temperatures into a more seasonable mid 60's to low 70's on the plains with low to mid 60's along the foothills. - Mostly sunny skies to start the day with clouds gradually increasing throughout the day. A chance this afternoon for scattered rain showers with a slight chance for an isolated thunderstorm if temperatures are able to warm enough. Best chance for thunderstorm activity will be from 3-7pm with rain shower chances possible into the overnight hours. Any shower activity should remain minimal this afternoon and evening, however a stronger storm cannot be completely ruled out favoring areas east of I-25 at this time. - Skies will gradually clear into Tuesday morning with overnight lows dipping into the low to mid 40's for the plains with low to mid 30's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers will produce a trace to 0.10" in 10-30 minutes. A weak to moderate thunderstorm could produce 0.1-0.3" of rain in 10-30 minutes. WORST CASE SCENARIO: A stronger thunderstorm or training of rain showers/thunderstorms has the potential to produce 0.3-0.8" in 60-90 minutes. A LOOK AHEAD: Tuesday will remain cooler with high temperatures in the mid to upper 60's along with mild and dry conditions. High-pressure returns Wednesday bringing high temperatures back into the 70's with continued dry conditions. Similar conditions both Thursday and Friday as high temperatures reach the low 80's. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (10%) NONE Arapahoe 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (10%) NONE Boulder 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Broomfield 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Denver 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Douglas 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Jefferson 300 PM TO 1159 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Foothills above 6500ft       Boulder 300 PM TO 1159 PM Trace (40%) to 0.1" (20%) to 0.3" (10%) NONE Douglas 300 PM TO 1159 PM Trace (40%) to 0.1" (20%) to 0.3" (10%) NONE Jefferson 300 PM TO 1159 PM Trace (40%) to 0.1" (20%) to 0.3" (10%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]