Flash Flood Prediction Program

Time: 115 PM Wed May 31, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT Message 1’s have been issued for the entire District and will be valid until 10:00pm this evening. Thunderstorms have initiated over the foothills and will begin to spread out onto the plains over the next couple hours. Thunderstorm coverage will be widely scattered with typical weak to moderate thunderstorms producing light to moderate rain and gusty winds. Stronger thunderstorms will be capable of producing brief heavy rainfall and may become severe with large hail and winds in excess of 50mph. A nearly stationary thunderstorm that forms along a gust front or wind convergence boundary will produce the greatest threat for an extended period of heavy rain today that may lead to excessive runoff and possibly flash flooding. 1-3 rounds of showers and thunderstorms are expected to move through the District into the evening. Best chances for moderate to strong thunderstorms will be through 9 or 10pm then additional showers and weaker thunderstorms will be possible into the early overnight period. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.3” of rain in 10-30 minutes. Strong thunderstorms will have the potential to produce rainfall rates of 0.3-0.8” in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 1.5” of rain in 45-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 100 PM TO 1000 PM 200 PM TO 900 PM Jefferson County 1 100 PM TO 1000 PM 200 PM TO 900 PM Broomfield County 1 100 PM TO 1000 PM 200 PM TO 900 PM Douglas County 1 100 PM TO 1000 PM 200 PM TO 900 PM Adams County 1 100 PM TO 1000 PM 200 PM TO 900 PM Denver County 1 100 PM TO 1000 PM 200 PM TO 900 PM DIA 1 100 PM TO 1000 PM 200 PM TO 900 PM Arapahoe County 1 100 PM TO 1000 PM 200 PM TO 900 PM the City of Aurora 1 100 PM TO 1000 PM 200 PM TO 900 PM Arvada 1 100 PM TO 1000 PM 200 PM TO 900 PM Wheat Ridge 1 100 PM TO 1000 PM 200 PM TO 900 PM Lakewood 1 100 PM TO 1000 PM 200 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Arapahoe Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Boulder Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Broomfield Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Denver Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Douglas Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Jefferson Current TO 1000 PM WED 0.1" (85%) to 0.3" (55%) to 0.8" (25%) ISSUED Foothills above 6500ft       Boulder Current TO 1000 PM WED 0.1" (95%) to 0.3" (65%) to 0.8" (35%) ISSUED Douglas Current TO 1000 PM WED 0.1" (95%) to 0.3" (65%) to 0.8" (35%) ISSUED Jefferson Current TO 1000 PM WED 0.1" (95%) to 0.3" (65%) to 0.8" (35%) 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]