Flash Flood Prediction Program

Time: 1228 PM Thu July 6, 2023 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 10:00 PM this evening. Multiple ingredients are in place today for thunderstorms to become strong to severe in and around the District. The first storms are beginning to develop over the foothills and these initial storms may dissipate as the air mass is still a little cool to support surface based convection over the plains. As the afternoon progresses storms are expected to blossom and become scattered producing brief heavy rainfall, hail, gusty winds and possibly a very isolated tornado. Typical storms will move from W to E or NNW to ESE at 20-25mph with stronger storms possibly splitting and moving more slowly/erratically. Fast storm motions will help to reduce point rainfall amounts, but a large thunderstorm or training of thunderstorm cells could produce extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.5” of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.5” in 10-30 minutes. WORST CASE SCENARIO: A slower moving large thunderstorm or training of thunderstorm cells may result in up to 2.5” of rain in 45-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1000 PM 130 PM TO 900 PM Jefferson County 1 Current TO 1000 PM 130 PM TO 900 PM Broomfield County 1 Current TO 1000 PM 130 PM TO 900 PM Douglas County 1 Current TO 1000 PM 130 PM TO 900 PM Adams County 1 Current TO 1000 PM 130 PM TO 900 PM Denver County 1 Current TO 1000 PM 130 PM TO 900 PM DIA 1 Current TO 1000 PM 130 PM TO 900 PM Arapahoe County 1 Current TO 1000 PM 130 PM TO 900 PM the City of Aurora 1 Current TO 1000 PM 130 PM TO 900 PM Arvada 1 Current TO 1000 PM 130 PM TO 900 PM Wheat Ridge 1 Current TO 1000 PM 130 PM TO 900 PM Lakewood 1 Current TO 1000 PM 130 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 1000 PM 0.1" (95%) to 0.5" (60%) to 1.5" (30%) ISSUED Arapahoe 100 PM TO 1000 PM 0.1" (95%) to 0.5" (60%) to 1.5" (30%) ISSUED Boulder 100 PM TO 1000 PM 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Broomfield 100 PM TO 1000 PM 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Denver 100 PM TO 1000 PM 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Douglas Current TO 1000 PM THU 0.1" (95%) to 0.5" (60%) to 1.5" (30%) ISSUED Jefferson Current TO 1000 PM THU 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Foothills above 6500ft       Boulder Current TO 1000 PM THU 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Douglas Current TO 1000 PM THU 0.1" (95%) to 0.5" (60%) to 1.5" (25%) ISSUED Jefferson Current TO 1000 PM THU 0.1" (95%) to 0.5" (60%) 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]