Time: 1014 AM Sun August 15, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ISOLATED TO WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS - A few passing light showers/sprinkles moved through the District earlier this morning associated with a weak upper level disturbance. Conditions will trend dry through the remainder of the morning with thunderstorms initiating over the foothills as early as noon. - Isolated to widely scattered thunderstorms will spread out onto the plains between 1-3pm with prime time through about 8 or 9pm this evening. The storms that develop today will be relatively fast moving from NW to SE at around 20mph which will help to limit point rainfall amounts from a single storm. Typical storms today will produce brief light to moderate rain with training of thunderstorm cells producing the greatest risk for extended periods of rain. - Although the majority of the thunderstorm activity is expected to remain weak to moderate in nature a stronger storm cannot be ruled out and will have the potential to produce brief heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" of rain. Moderate to briefly strong thunderstorms will have the potential to produce 0.2-0.6" of rain in 10-30 minutes. WORST CASE SCENARIO: Training of moderate to strong thunderstorm cells may result in up to 1.2" of heavy rainfall in 45-60 minutes. A LOOK AHEAD: Tomorrow, smoke from wildfires burning to our west will increase haze and reduce visibilities. Thunderstorm activity Monday afternoon is expected to be isolated and generally limited to the higher terrain with the plains on the drier side. Another day with minimal thunderstorm activity on Tuesday then chances for heavy rainfall producing thunderstorms increases on Wednesday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM Trace (80%) to 0.2" (40%) to 0.6" (20%) LOW Arapahoe 200 PM TO 900 PM Trace (80%) to 0.2" (40%) to 0.6" (20%) LOW Broomfield 200 PM TO 900 PM Trace (80%) to 0.2" (40%) to 0.6" (20%) LOW Denver 200 PM TO 900 PM Trace (80%) to 0.2" (40%) to 0.6" (20%) LOW Boulder 100 PM TO 900 PM Trace (90%) to 0.2" (50%) to 0.6" (25%) LOW Douglas 100 PM TO 900 PM Trace (90%) to 0.2" (50%) to 0.6" (25%) LOW Jefferson 100 PM TO 900 PM Trace (90%) to 0.2" (50%) to 0.6" (25%) LOW Foothills above 6500ft       Boulder 1200 PM TO 900 PM Trace (95%) to 0.2" (60%) to 0.6" (30%) LOW Douglas 1200 PM TO 900 PM Trace (95%) to 0.2" (60%) to 0.6" (30%) LOW Jefferson 1200 PM TO 900 PM Trace (95%) to 0.2" (60%) to 0.6" (30%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]