Flash Flood Prediction Program

Time: 603 PM Sun August 21, 2022 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONTINUE VALID FOR THE ENTIRE DISTRICT/HEAVY RAINFALL THREAT LOWERING - Message 1's will continue valid until 9:00 PM but the threat for heavy rainfall is diminishing now that temperatures are cooling. - A line of moderate to strong thunderstorms develop along a surface wind convergence line or Denver Convergence Vorticity Zone (DCVZ) that extended from Douglas County northeastward into Arapahoe and Adams County including the DIA portion of Denver County. These storms have peaked in intensity over the past hour and the boundary is washing out resulting in a lower threat for thunderstorms with the potential for heavy rainfall into the evening. - A weak gust front is progressing eastward from these original storms and when it reaches the foothills may generate new storms but with a cooling airmass the threat for new development is low. Should a new round of thunderstorms develop, stronger storms will have the potential to produce brief heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a 0.2-0.6" of rainfall in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.4-1.0" in 10-30 minutes. WORST CASE SCENARIO: A strong, stationary thunderstorm or training of thunderstorm may result in up to 2.0" of heavy rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 100 PM TO 900 PM 200 PM TO 830 PM Wheat Ridge 1 100 PM TO 900 PM 200 PM TO 830 PM Arvada 1 100 PM TO 900 PM 200 PM TO 830 PM the City of Aurora 1 100 PM TO 900 PM 200 PM TO 830 PM Arapahoe County 1 100 PM TO 900 PM 200 PM TO 830 PM DIA 1 100 PM TO 900 PM 200 PM TO 830 PM Denver County 1 100 PM TO 900 PM 200 PM TO 830 PM Adams County 1 100 PM TO 900 PM 200 PM TO 830 PM Douglas County 1 100 PM TO 900 PM 200 PM TO 830 PM Broomfield County 1 100 PM TO 900 PM 200 PM TO 830 PM Jefferson County 1 100 PM TO 900 PM 200 PM TO 830 PM Boulder County 1 100 PM TO 900 PM 200 PM TO 830 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 900 PM SUN Trace (95%) to 0.2" (60%) to 0.6" (30%) ISSUED Arapahoe Current TO 900 PM SUN Trace (90%) to 0.2" (60%) to 0.6" (20%) ISSUED Boulder Current TO 900 PM SUN Trace (75%) to 0.2" (50%) to 0.6" (10%) ISSUED Broomfield Current TO 900 PM SUN Trace (75%) to 0.2" (50%) to 0.6" (10%) ISSUED Denver Current TO 900 PM SUN Trace (80%) to 0.2" (40%) to 0.6" (15%) ISSUED Douglas Current TO 900 PM SUN Trace (80%) to 0.2" (40%) to 0.6" (15%) ISSUED Jefferson Current TO 900 PM SUN Trace (75%) to 0.2" (50%) to 0.6" (10%) ISSUED Foothills above 6500ft       Boulder Current TO 900 PM SUN Trace (95%) to 0.2" (60%) to 0.6" (30%) ISSUED Douglas Current TO 900 PM SUN Trace (95%) to 0.2" (60%) to 0.6" (30%) ISSUED Jefferson Current TO 900 PM SUN Trace (95%) to 0.2" (60%) to 0.6" (30%) 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]