Flash Flood Prediction Program

Time: 702 PM Thu July 29, 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 NW portions of the District as a surface wind convergence boundary is in place and weak storms are beginning to develop over Boulder and Broomfield Counties. - A warm layer of air aloft results in uncertainty if the current storms can maintain or strengthen but with ample surface moisture in place if a stronger storm is able to develop it will contain heavy rainfall. Best chances for storms are near the surface wind convergence over NW portions of the District but these storms may produce their own outflow boundaries and produce additional storms which may become strong may lead to Message 1's being issued for the remainder of the District as the evening wears on. - Thunderstorms will be slow moving due to weak steering winds aloft. Best chances for thunderstorms will be through 10pm this evening. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.3" of rain. Moderate to strong thunderstorms will have the potential to produce 0.4-1.2" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A stationary strong thunderstorm will have the potential to produce up to 2.5" in 45-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Adams County 1 Current TO 1000 PM Current TO 900 PM Broomfield County 1 Current TO 1000 PM Current TO 900 PM Jefferson County 1 Current TO 1000 PM Current TO 900 PM Boulder County 1 Current TO 1000 PM Current TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 PM THU 0.1" (60%) to 0.4" (25%) to 1.2" (10%) ISSUED Arapahoe Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) MOD Boulder Current TO 1000 PM THU 0.1" (80%) to 0.4" (50%) to 1.2" (25%) ISSUED Broomfield Current TO 1000 PM THU 0.1" (80%) to 0.4" (50%) to 1.2" (25%) ISSUED Denver Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) MOD Douglas Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) LOW Jefferson Current TO 1000 PM THU 0.1" (60%) to 0.4" (25%) to 1.2" (10%) ISSUED Foothills above 6500ft       Boulder Current TO 1000 PM THU 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Douglas Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) LOW Jefferson Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (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]