Flash Flood Prediction Program

Time: 616 PM Thu July 20, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL CONTINUE VALID UNTIL 11:59 PM Message 1’s will continue to be valid as the threat for heavy rainfall continues as yet another round or two of showers and thunderstorms are expected this evening. A new batch of showers and thunderstorms are developing to the W and will be moving through the District over the next 1-4 hours. These evening thunderstorms are expected to be weaker than previous storms today but with surface dew points in the upper 50's to mid 60's the storms that do develop will be efficient rainfall producing storms and even a moderate thunderstorm will be capable of producing brief heavy rainfall. Some areas of the District have also experienced wetting rains and the ground may be becoming saturated and it may not take as much rain to produce excessive runoff in areas that have already been impacted by strong thunderstorms. Thunderstorms will continue to be fast moving from W to E at 20-25mph for typical storms with stronger storms possibly moving more NW to SE. After 9 or 10pm the threat for thunderstorms will to diminish and Message 4's (All Clear) may be issued prior to midnight should generally dry conditions develop. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce 0.1-0.5” in 10-30 minutes. A moderate to strong thunderstorm will produce 0.5-1.2” in 10-30 minutes. WORST CASE SCENARIO: A slower moving strong thunderstorm or training of thunderstorm cells has the potential to produce up to 2.0” in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1159 PM Current TO 1000 PM Jefferson County 1 Current TO 1159 PM Current TO 1000 PM Broomfield County 1 Current TO 1159 PM Current TO 1000 PM Douglas County 1 Current TO 1159 PM Current TO 1000 PM Adams County 1 Current TO 1159 PM Current TO 1000 PM Denver County 1 Current TO 1159 PM Current TO 1000 PM DIA 1 Current TO 1159 PM Current TO 1000 PM Arapahoe County 1 Current TO 1159 PM Current TO 1000 PM the City of Aurora 1 Current TO 1159 PM Current TO 1000 PM Arvada 1 Current TO 1159 PM Current TO 1000 PM Wheat Ridge 1 Current TO 1159 PM Current TO 1000 PM Lakewood 1 Current TO 1159 PM Current TO 1000 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Arapahoe Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Boulder Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Broomfield Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Denver Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Douglas Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Foothills above 6500ft       Boulder Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Douglas Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (70%) to 0.5" (40%) to 1" (15%) 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]