Flash Flood Prediction Program

Time: 203 PM Fri July 9, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- MOISTURE NORTH OF THE DISTRICT MAY COME INTO PLAY LATER THIS AFTERNOON... - Easterly surface winds have increased surface moisture, in particular N of the District with dew points well into the 50's over Weld and Larimer Counties. As the afternoon progresses stronger storms are expected to develop over northern Colorado and may produce a rain cooled gust front that moves south into the District supplying a trigger for storms as well as importing additional moisture. - If all the ingredients come together just right a strong storms with brief heavy rainfall cannot be ruled out later this afternoon or evening resulting in a LOW Message potential. The most likely outcome is higher based weak to moderate thunderstorms producing light to briefly moderate rain with enhanced moisture remaining north. - Upper level steering winds are from NW to SE at 20-25mph keeping rainfall brief. An outflow boundary or gust front may allow for a storm to anchor briefly and produce prolonged periods of rainfall. Best chances for thunderstorm activity is through about sunset. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.2-0.6" in 10-30 minutes. WORST CASE SCENARIO: A slower moving strong thunderstorm may result in up to 1.3" in 45-60 minutes. A LOOK AHEAD: A reprieve from the heat this weekend as cooler temperatures ascend on us from the north. A very slight chance for rain showers/isolated thunderstorms Saturday afternoon with heavy rainfall not anticipated at this time. Saturday and Sunday will be cooler with temperatures in the low to mid 80's. Dry conditions are likely both Sunday and Monday with storm chances picking up into Tuesday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM Trace (60%) to 0.3" (30%) to 0.6" (10%) LOW Arapahoe 300 PM TO 900 PM Trace (60%) to 0.3" (30%) to 0.6" (10%) LOW Boulder 300 PM TO 900 PM Trace (75%) to 0.3" (30%) to 0.6" (10%) LOW Broomfield 300 PM TO 900 PM Trace (60%) to 0.3" (30%) to 0.6" (10%) LOW Denver 300 PM TO 900 PM Trace (60%) to 0.3" (30%) to 0.6" (10%) LOW Douglas 300 PM TO 900 PM Trace (75%) to 0.3" (30%) to 0.6" (10%) LOW Jefferson 300 PM TO 900 PM Trace (75%) to 0.3" (30%) to 0.6" (10%) LOW Foothills above 6500ft       Boulder Current TO 900 PM FRI Trace (85%) to 0.3" (30%) to 0.6" (10%) LOW Douglas Current TO 900 PM FRI Trace (85%) to 0.3" (30%) to 0.6" (10%) LOW Jefferson Current TO 900 PM FRI Trace (85%) to 0.3" (30%) to 0.6" (10%) 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]