Time: 452 PM Fri July 30, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT/MESSAGE 2'S BECOME VALID AT 6PM - Message 1's have been issued for the entire District and will be valid until 6:00pm then the Message 1's will be upgraded to Message 2's to coincide with the NWS Flash Flood Watch. - A cold front is on the approach and is already producing strong thunderstorms over northern Colorado. As the front moves southward thunderstorms are expected to develop behind it becoming strong to severe with the potential to produce extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. - Moisture levels are expected to be higher than at any point this season later today and tomorrow and will result in efficient rainfall producing storms. The greatest threat for heavy rain from thunderstorms will be through about midnight then rain showers may be capable of producing up to 1"/hr or higher rainfall rates overnight. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm will have the potential to produce up to 3.5" in 45-60 minutes. Storms that persist beyond 60 minutes may produce locally higher amounts. COUNTY MESSAGE VALID TIMES PRIME TIME Broomfield County 1 Current TO 600 PM 500 PM TO 600 PM Jefferson County 1 Current TO 600 PM 500 PM TO 600 PM Boulder County 1 Current TO 600 PM 500 PM TO 600 PM Wheat Ridge 1 Current TO 600 PM 500 PM TO 600 PM Arvada 1 Current TO 600 PM 500 PM TO 600 PM the City of Aurora 1 Current TO 600 PM 500 PM TO 600 PM Arapahoe County 1 Current TO 600 PM 500 PM TO 600 PM DIA 1 Current TO 600 PM 500 PM TO 600 PM Denver County 1 Current TO 600 PM 500 PM TO 600 PM Adams County 1 Current TO 600 PM 500 PM TO 600 PM Douglas County 1 Current TO 600 PM 500 PM TO 600 PM Lakewood 1 Current TO 600 PM 500 PM TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Arapahoe 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Boulder 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Broomfield 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Denver 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Douglas 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Jefferson 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Foothills above 6500ft       Boulder 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Douglas 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Jefferson 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]