Flash Flood Prediction Program

Time: 419 PM Fri August 18, 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 for the entire District effective until 9:00pm as the threat of heavy rainfall has increased into the late afternoon and evening. A few weak showers and thunderstorms moved across the District this afternoon. A stronger line of showers and thunderstorms is currently moving in from the SW and will progress through the District over the next few hours. This line of storms will have the potential to produce localized heavy rainfall leading to isolated LOW IMPACT FLOODING for portions of the District. The main threat will likely be a quick 0.4-0.6” in 10-15 minutes, rather than long lasting heavy rainfall. Storms will generally move from the SW to NE between 10-15mph, which should help limit point rainfall amounts, although a gust front from a stronger storm will have the potential to produce erratic storm movements from storms initiating off these outflow boundaries. Storm chances will decrease after sunset with a few lingering showers possible through 10pm. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.30” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.30-0.60” total in 10-30 minutes. WORST CASE SCENARIO: A strong, stationary thunderstorm, or training of thunderstorm cells will have the potential to produce 0.60-1.20” total in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 900 PM Current TO 800 PM Wheat Ridge 1 Current TO 900 PM Current TO 800 PM Arvada 1 Current TO 900 PM Current TO 800 PM the City of Aurora 1 Current TO 900 PM Current TO 800 PM Arapahoe County 1 Current TO 900 PM Current TO 800 PM DIA 1 Current TO 900 PM Current TO 800 PM Denver County 1 Current TO 900 PM Current TO 800 PM Adams County 1 Current TO 900 PM Current TO 800 PM Douglas County 1 Current TO 900 PM Current TO 800 PM Broomfield County 1 Current TO 900 PM Current TO 800 PM Jefferson County 1 Current TO 900 PM Current TO 800 PM Boulder County 1 Current TO 900 PM Current TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Arapahoe Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Boulder Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Broomfield Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Denver Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Douglas Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Jefferson Current TO 900 PM FRI 0.05" (75%) to 0.3" (50%) to 0.6" (25%) ISSUED Foothills above 6500ft       Boulder Current TO 900 PM FRI 0.05" (80%) to 0.3" (40%) to 0.6" (30%) ISSUED Douglas Current TO 900 PM FRI 0.05" (80%) to 0.3" (40%) to 0.6" (30%) ISSUED Jefferson Current TO 900 PM FRI 0.05" (80%) to 0.3" (40%) 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]