Flash Flood Prediction Program

Time: 1159 AM Sat June 19, 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 this evening. - Modest surface moisture in tandem with a passing upper level disturbance will result in a round of thunderstorms this afternoon. Relatively fast storm motions from W to E at around 20mph will keep the potential for heavy rainfall short lived most areas. Training of thunderstorm cells or a large, slower moving strong thunderstorm will have the potential to produce an extended period of heavy rain that may lead to excessive runoff. - Strong thunderstorms that develop today may also become severe with gusty winds in excess of 50mph, large hail of 1" or more in diameter being the primary threats. Generally one round of thunderstorms is expected but some areas could see a couple rounds of thunderstorm activity. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will have the potential to produce 0.3-0.9" in 10-30 minutes. WORST CASE SCENARIO: A large, slower moving thunderstorm or training of thunderstorm cells will have the potential to produce up to 1.6" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 1200 PM TO 800 PM 130 PM TO 700 PM Jefferson County 1 1200 PM TO 800 PM 130 PM TO 700 PM Broomfield County 1 1200 PM TO 800 PM 130 PM TO 700 PM Douglas County 1 1200 PM TO 800 PM 130 PM TO 700 PM Adams County 1 1200 PM TO 800 PM 130 PM TO 700 PM Denver County 1 1200 PM TO 800 PM 130 PM TO 700 PM DIA 1 1200 PM TO 800 PM 130 PM TO 700 PM Arapahoe County 1 1200 PM TO 800 PM 130 PM TO 700 PM the City of Aurora 1 1200 PM TO 800 PM 130 PM TO 700 PM Arvada 1 1200 PM TO 800 PM 130 PM TO 700 PM Wheat Ridge 1 1200 PM TO 800 PM 130 PM TO 700 PM Lakewood 1 1200 PM TO 800 PM 130 PM TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1230 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.9" (30%) ISSUED Arapahoe 1230 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.9" (30%) ISSUED Boulder 1230 PM TO 800 PM 0.1" (90%) to 0.3" (50%) to 0.9" (25%) ISSUED Broomfield 1230 PM TO 800 PM 0.1" (90%) to 0.3" (50%) to 0.9" (25%) ISSUED Denver 1230 PM TO 800 PM 0.1" (90%) to 0.3" (50%) to 0.9" (30%) ISSUED Douglas 1230 PM TO 800 PM 0.1" (90%) to 0.3" (50%) to 0.9" (25%) ISSUED Jefferson 1230 PM TO 800 PM 0.1" (90%) to 0.3" (50%) to 0.9" (25%) ISSUED Foothills above 6500ft       Boulder Current TO 800 PM SAT 0.1" (95%) to 0.3" (50%) to 0.9" (20%) ISSUED Douglas Current TO 800 PM SAT 0.1" (95%) to 0.3" (50%) to 0.9" (20%) ISSUED Jefferson Current TO 800 PM SAT 0.1" (95%) to 0.3" (50%) to 0.9" (20%) 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]