Time: 1144 AM Fri September 3, 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 until 8:00pm. An upper level disturbance is on the approach and is expected to produce 1-2 rounds of thunderstorms this afternoon. Stronger thunderstorms will be capable of producing brief heavy rainfall, gusty winds and hail. - Steering winds from SW to NE at 15-20mph will keep storms moving along at a brisk pace but stronger storms will be capable of producing heavy rainfall that may lead to excessive runoff. Favored areas for stronger storms looks to be along and E of I-25 where moisture is deeper. Storms are currently starting to fill in over NW portions of the District and will spread to the SE as the afternoon progresses. - After 7 or 8pm the main round or two of storms is expected to have pushed eastward with lingering more isolated light rain showers remaining possible until around 10pm. Beyond 10pm dry conditions are expected for the remainder of the evening/overnight period. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.1-0.4" of rainfall in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce heavy rainfall of 0.4-1.2" in 10-30 minutes. WORST CASE SCENARIO: Training of strong thunderstorm cells or a slower moving large thunderstorm may result in up to 2.4" of rainfall in 60-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 1200 PM TO 800 PM 100 PM TO 700 PM Jefferson County 1 1200 PM TO 800 PM 100 PM TO 700 PM Broomfield County 1 1200 PM TO 800 PM 100 PM TO 700 PM Douglas County 1 1200 PM TO 800 PM 100 PM TO 700 PM Adams County 1 1200 PM TO 800 PM 100 PM TO 700 PM Denver County 1 1200 PM TO 800 PM 100 PM TO 700 PM DIA 1 1200 PM TO 800 PM 100 PM TO 700 PM Arapahoe County 1 1200 PM TO 800 PM 100 PM TO 700 PM the City of Aurora 1 1200 PM TO 800 PM 100 PM TO 700 PM Arvada 1 1200 PM TO 800 PM 100 PM TO 700 PM Wheat Ridge 1 1200 PM TO 800 PM 100 PM TO 700 PM Lakewood 1 1200 PM TO 800 PM 100 PM TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (25%) ISSUED Arapahoe Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (25%) ISSUED Boulder Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (20%) ISSUED Broomfield Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (20%) ISSUED Denver Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (25%) ISSUED Douglas Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (25%) ISSUED Jefferson Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (20%) ISSUED Foothills above 6500ft       Boulder Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (15%) ISSUED Douglas Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (15%) ISSUED Jefferson Current TO 800 PM FRI 0.1" (90%) to 0.4" (60%) to 1.2" (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]