Time: 1244 PM Sun September 3, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S HAVE BEEN ISSUED EFFECTIVE UNTIL 9:00 PM Message 1’s have been issued effective until 9pm as there is a threat of heavy rainfall this afternoon and into this evening. A few moderate to strong storms have formed along the foothills and should begin moving into the District over the next hour or so. Multiple rounds of showers/thunderstorms will be possible with the last round likely tapering off by 9pm. The largest threat for storms today will be a quick 0.50-0.60” in 10-15 minutes, with a low threat for any rainfall over an inch as most storms move between 10-15mph. These SW to NE storm motions should help limit point rainfall amounts, however, a stronger storm has the potential to produce longer lasting moderate to heavy rainfall. A gust front from a strong storm could result in additional storm development with erratic or slower moving storm motions throughout the District. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce rainfall of a 0.05” to 0.25” total in 10-30 minutes. Moderate to strong showers/thunderstorms have the will produce rainfall of 0.25 to 0.75” total in 10-30 minutes. WORST CASE SCENARIO: Strong stationery, or training of thunderstorms has the potential to produce 0.75” to 1.50” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 900 PM 100 PM TO 830 PM Jefferson County 1 Current TO 900 PM 100 PM TO 830 PM Broomfield County 1 Current TO 900 PM 100 PM TO 830 PM Douglas County 1 Current TO 900 PM 100 PM TO 830 PM Adams County 1 Current TO 900 PM 100 PM TO 830 PM Denver County 1 Current TO 900 PM 100 PM TO 830 PM DIA 1 Current TO 900 PM 100 PM TO 830 PM Arapahoe County 1 Current TO 900 PM 100 PM TO 830 PM the City of Aurora 1 Current TO 900 PM 100 PM TO 830 PM Arvada 1 Current TO 900 PM 100 PM TO 830 PM Wheat Ridge 1 Current TO 900 PM 100 PM TO 830 PM Lakewood 1 Current TO 900 PM 100 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 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Arapahoe Current TO 900 PM SUN 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Boulder Current TO 900 PM SUN 0.05" (90%) to 0.25" (50%) to 0.75" (30%) ISSUED Broomfield Current TO 900 PM SUN 0.05" (85%) to 0.25" (45%) to 0.75" (25%) ISSUED Denver Current TO 900 PM SUN 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Douglas Current TO 900 PM SUN 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Jefferson Current TO 900 PM SUN 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Foothills above 6500ft       Boulder Current TO 900 PM SUN 0.05" (100%) to 0.25" (75%) to 0.75" (50%) ISSUED Douglas Current TO 900 PM SUN 0.05" (80%) to 0.25" (40%) to 0.75" (20%) ISSUED Jefferson Current TO 900 PM SUN 0.05" (90%) to 0.25" (60%) to 0.75" (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]