Flash Flood Prediction Program

Time: 937 AM Tue July 6, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH LESS THUNDERSTORM ACTIVITY EXPECTED OVER THE PLAINS - Behind a cold front that moved through before daybreak temperatures will be cooler over the District today. Temperatures will peak in the upper 70's to lower 80's over the plains which is about 10 degrees below normal. Normal high for Denver today is 89 degrees. - The cooler temperatures will push back the timing for thunderstorms by an hour or two and if temperatures remain too cool over the plains (mid/upper 70's) convection may be limited to the foothills and Palmer Divide only. With sunny skies currently the thinking is that temperatures warm enough for at least isolated afternoon thunderstorms over the plains with scattered coverage in the foothills. There is plenty of moisture available today with over 1" of precipitable water at the 6am sounding and stronger storms should they develop will have the potential to produce heavy rainfall. - Thunderstorms will develop over the mountains and foothills between 1-2pm with thunderstorm chances spreading out onto the plains between 2-4pm with NW to SE upper level steering winds. Best chances for thunderstorm activity will be through 8pm. Additional rain showers and possibly a weak thunderstorm remains possible into the evening with completely dry conditions by around midnight. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.30" of rain. Moderate to strong thunderstorms will have the potential to produce 0.3-0.8" of rain in 10-30 minutes. WORST CASE SCENARIO: A strong, slow moving thunderstorm may result in up to 1.6" of heavy rain in 45-60 minutes. A LOOK AHEAD: Drier air will be moving into the District on Wednesday with temperatures warming into the mid 80's to around 90 for highs over the plains. Dry conditions are expected over the lower elevations with possibly a very isolated thunderstorm in the foothills. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 800 PM 0.1" (40%) to 0.3" (20%) to 0.8" (10%) LOW Arapahoe 300 PM TO 800 PM 0.1" (40%) to 0.3" (20%) to 0.8" (10%) LOW Broomfield 300 PM TO 800 PM 0.1" (40%) to 0.3" (20%) to 0.8" (10%) LOW Denver 300 PM TO 800 PM 0.1" (40%) to 0.3" (20%) to 0.8" (10%) LOW Boulder 200 PM TO 800 PM 0.1" (70%) to 0.3" (40%) to 0.8" (15%) MOD Douglas 200 PM TO 800 PM 0.1" (75%) to 0.3" (40%) to 0.8" (15%) MOD Jefferson 200 PM TO 800 PM 0.1" (75%) to 0.3" (40%) to 0.8" (15%) MOD Foothills above 6500ft       Boulder 100 PM TO 800 PM 0.1" (85%) to 0.3" (60%) to 0.8" (25%) MOD Douglas 100 PM TO 800 PM 0.1" (85%) to 0.3" (60%) to 0.8" (25%) MOD Jefferson 100 PM TO 800 PM 0.1" (85%) to 0.3" (60%) to 0.8" (25%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]