Flash Flood Prediction Program

Time: 1041 PM Thu August 12, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR PORTIONS OF THE DISTRICT - Message 1's have been issued for all areas of the District EXCEPT Boulder and Broomfield Counties at this time. Boulder and Broomfield Counties may be included over the next hour. - An outflow boundary has moved into the District and is beginning to initiate thunderstorm development along the I-25 corridor S of I-70 currently. These storms are expected to become stronger and will have the potential to produce heavy rainfall this evening and overnight. - Best chances for thunderstorm activity will be along and E of the I-25 corridor where moisture is deeper with a lesser chance for strong storms further W, but conditions may evolve. Best chances for thunderstorms will be until about 2am Friday morning. Should thunderstorm activity linger through 3am, Message 1's may need to be extended. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.2-0.5" in 10-30 minutes. Strong thunderstorms will have the potential to produce heavy rainfall of 0.5-1.5" 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 Jefferson County 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Douglas County 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Adams County 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Denver County 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY DIA 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Arapahoe County 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY the City of Aurora 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Arvada 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Wheat Ridge 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY Lakewood 1 Current TO 300 AM FRIDAY 1100 PM TO 200 AM FRIDAY County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 300 AM FRI 0.2" (90%) to 0.5" (60%) to 1.5" (30%) ISSUED Arapahoe Current TO 300 AM FRI 0.2" (100%) to 0.5" (80%) to 1.5" (40%) ISSUED Boulder Current TO 300 AM FRI 0.2" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Broomfield Current TO 300 AM FRI 0.2" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Denver Current TO 300 AM FRI 0.2" (100%) to 0.5" (80%) to 1.5" (40%) ISSUED Douglas Current TO 300 AM FRI 0.2" (100%) to 0.5" (80%) to 1.5" (40%) ISSUED Jefferson Current TO 300 AM FRI 0.2" (90%) to 0.5" (60%) to 1.5" (30%) ISSUED Foothills above 6500ft       Boulder Current TO 300 AM FRI 0.2" (60%) to 0.5" (40%) to 1.5" (20%) HIGH Douglas Current TO 300 AM FRI 0.2" (100%) to 0.5" (80%) to 1.5" (40%) ISSUED Jefferson Current TO 300 AM FRI 0.2" (80%) to 0.5" (50%) to 1.5" (25%) 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]