Flash Flood Prediction Program

Time: 1204 PM Mon July 5, 2021 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 from 1:00pm until 9:00pm this evening. - An approaching upper level disturbance is expected to result in a round or two of thunderstorms this afternoon and early evening. Storms that develop today will be very capable of producing heavy rainfall that may lead to excessive runoff and flash flooding. Storms will be slow moving as upper level steering winds are light from NW to SE at 5-10mph. Outflow boundaries and gust fronts may act to briefly anchor storms and may result in erratic storm motions at times. - After 9pm the threat for thunderstorm activity decreases but another round of showers is expected to move through and be in the area until around midnight. If the late evening round of showers also contains thunderstorm activity then Message 1's may need to be extended until midnight. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.4" of rainfall. Strong thunderstorms will have the potential to produce 0.4-1.2" in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.5" of heavy rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 100 PM TO 900 PM 200 PM TO 800 PM Jefferson County 1 100 PM TO 900 PM 200 PM TO 800 PM Broomfield County 1 100 PM TO 900 PM 300 PM TO 800 PM Douglas County 1 100 PM TO 900 PM 200 PM TO 800 PM Adams County 1 100 PM TO 900 PM 300 PM TO 800 PM Denver County 1 100 PM TO 900 PM 300 PM TO 800 PM DIA 1 100 PM TO 900 PM 300 PM TO 800 PM Arapahoe County 1 100 PM TO 900 PM 300 PM TO 800 PM the City of Aurora 1 100 PM TO 900 PM 300 PM TO 800 PM Arvada 1 100 PM TO 900 PM 300 PM TO 800 PM Wheat Ridge 1 100 PM TO 900 PM 300 PM TO 800 PM Lakewood 1 100 PM TO 900 PM 300 PM TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Arapahoe 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Broomfield 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Denver 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Boulder 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Douglas 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Jefferson 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Foothills above 6500ft       Boulder 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (30%) ISSUED Douglas 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (30%) ISSUED Jefferson 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (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]