Flash Flood Prediction Program

Time: 626 PM Thu June 30, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- TOO COOL FOR STRONG THUNDERSTORMS TODAY/HEAVY RAINFALL THREAT HAS DIMINISHED - The cloud cover this morning and isolated light shower activity through early afternoon held temperatures down into the 70's and lower 80's over the plains which was insufficient for the development of strong thunderstorms today over the District. Now that temperatures are in the 60's and 70's over the plains the threat for heavy rainfall has diminished. - There will still be a modest chance for rain shower activity and possibly a very isolated weak thunderstorms into the evening, favoring areas S of I-70 through 9 or 10pm but the overall trend is for showers to diminish over the coming hours. Additional, isolated light rain showers will continue possible after 10pm into the early overnight with dry conditions expected by midnight or shortly after. - Upper level steering winds will keep the remaining showers and thunderstorms this evening moving along briskly from WSW to ENE at around 25mph. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.1" in 10-30 minutes. Weak thunderstorms will produce rainfall rates of 0.1-0.3" in 10-30 minutes. WORST CASE SCENARIO: A moderate to strong thunderstorm is able to develop with the potential to produce heavy rainfall of 0.3-0.8" in 10-30 minutes. A LOOK AHEAD: Temperatures will decrease further on Friday with highs in the 70's to around 80 over the plains. Much like today there will be ample moisture to work with but will the cooler temperatures hinder the strong storms like today? The current thinking is... Yes, cooler temperatures will likely limit the potential for heavy rain, but there will still be shower and thunderstorm coverage with a low to possibly moderate threat for brief heavy rain. Greatest coverage of storms on Friday is likely S of I-70 and in particular over the southern foothills and Palmer Divide. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1159 PM THU Trace (50%) to 0.1" (20%) to 0.3" (5%) NONE Arapahoe Current TO 1159 PM THU Trace (75%) to 0.1" (40%) to 0.3" (10%) NONE Boulder Current TO 1159 PM THU Trace (75%) to 0.1" (40%) to 0.3" (10%) NONE Broomfield Current TO 1159 PM THU Trace (50%) to 0.1" (20%) to 0.3" (5%) NONE Denver Current TO 1159 PM THU Trace (60%) to 0.1" (30%) to 0.3" (5%) NONE Douglas Current TO 1159 PM THU Trace (75%) to 0.1" (40%) to 0.3" (10%) NONE Jefferson Current TO 1159 PM THU Trace (75%) to 0.1" (40%) to 0.3" (10%) NONE Foothills above 6500ft       Boulder Current TO 1159 PM THU Trace (80%) to 0.1" (50%) to 0.3" (15%) NONE Douglas Current TO 1159 PM THU Trace (80%) to 0.1" (50%) to 0.3" (15%) NONE Jefferson Current TO 1159 PM THU Trace (80%) to 0.1" (50%) to 0.3" (15%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]