Flash Flood Prediction Program

Time: 1249 PM Sat May 22, 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 1:00-8:00pm. Thunderstorms that develop today will be fast moving, but contain the risk of brief heavy rainfall that may lead to excessive runoff. - Very fast storm motions from S to N at 30-40mph will limit point rainfall amounts from a single storm. However, a surface wind convergence line currently located over central Douglas County extending E/NE could allow storms to anchor briefly or move more slowly. Training of multiple thunderstorm cells over a single location may also result in an extended period of heavy rainfall. - Thunderstorms that develop today will not only have the potential for heavy rainfall and may tend to become severe in nature with gusty winds in excess of 60mph, large hail of 1" or more in diameter and possibly a very isolated tornado. Best chances for strong/severe storms will be between 1:30-7:00pm. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers and thunderstorms will have the potential to produce 0.1-0.3" in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.3-0.7" in 10-30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells may result in up to 1.5" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 100 PM TO 800 PM 200 PM TO 700 PM Jefferson County 1 100 PM TO 800 PM 200 PM TO 700 PM Broomfield County 1 100 PM TO 800 PM 200 PM TO 700 PM Douglas County 1 100 PM TO 800 PM 130 PM TO 700 PM Adams County 1 100 PM TO 800 PM 200 PM TO 700 PM Denver County 1 100 PM TO 800 PM 200 PM TO 700 PM DIA 1 100 PM TO 800 PM 200 PM TO 700 PM Arapahoe County 1 100 PM TO 800 PM 130 PM TO 700 PM the City of Aurora 1 100 PM TO 800 PM 200 PM TO 700 PM Arvada 1 100 PM TO 800 PM 200 PM TO 700 PM Wheat Ridge 1 100 PM TO 800 PM 200 PM TO 700 PM Lakewood 1 100 PM TO 800 PM 200 PM TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.7" (30%) ISSUED Arapahoe 100 PM TO 800 PM 0.1" (95%) to 0.3" (75%) to 0.7" (35%) ISSUED Boulder 100 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.7" (30%) ISSUED Broomfield 100 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.7" (30%) ISSUED Denver 100 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.7" (30%) ISSUED Douglas 100 PM TO 800 PM 0.1" (95%) to 0.3" (75%) to 0.7" (35%) ISSUED Jefferson 100 PM TO 800 PM 0.1" (90%) to 0.3" (60%) to 0.7" (30%) ISSUED Foothills above 6500ft       Boulder Current TO 800 PM SAT 0.1" (95%) to 0.3" (60%) to 0.7" (30%) ISSUED Douglas Current TO 800 PM SAT 0.1" (95%) to 0.3" (75%) to 0.7" (35%) ISSUED Jefferson Current TO 800 PM SAT 0.1" (95%) to 0.3" (60%) to 0.7" (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]