Time: 924 AM Thu June 30, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- RAIN SHOWERS AND THUNDERSTORMS EXPECTED/THE STRENGTH OF THE STORMS REMAIN IN QUESTION - Much cooler today over the District with high temperatures in the 80's for highs over the plains with 70's in the Front Range foothills. Surface moisture has increased and with the aid of an upper level disturbance showers and thunderstorms will be more numerous today. Stronger thunderstorms will be capable of producing heavy rainfall but with cloud cover this morning temperatures may not warm sufficiently to generate strong storms and the majority of the activity may trend more weak to moderate. More sun this morning would lead to a better chance of stronger storms this afternoon. - Isolated to widely scattered light rain showers will fill in this morning with chances for thunderstorms increasing after the noon hour. Multiple rounds of showers and weak to moderate thunderstorms are expected through the afternoon and into the early evening. Prime time for thunderstorm activity will be from 1-9pm. Additional rain showers and possibly a weak thunderstorm will continue possible until midnight then generally dry conditions are expected after midnight into Friday morning. - Upper level steering winds will be from WSW to ENE at around 20mph which will keep individual storms moving along and any heavy rainfall relatively brief. Surface wind convergence may allow for a thunderstorm to anchor briefly or move more slowly allowing for a longer period of moderate to heavy rainfall which may lead to excessive runoff. Multiple ingredients are in place for heavy rainfall today resulting in a moderate risk for Message issuance but fast storm motions and cloud cover limiting the daytime heating may keep the heavy rainfall at bay? STORM RAINFALL POTENTIAL AND DURATION: Moderate non-thunderstorm rain showers and weak thunderstorms will produce 0.1-0.3" of rain in 30-60 minutes. Moderate to briefly strong thunderstorms will have the potential to produce rainfall rates of 0.3-0.8" in 10-30 minutes. WORST CASE SCENARIO: Strong, slower moving thunderstorms if able to develop will have the potential to produce heavy rainfall rates of 0.5-1.2" in 10-30 minutes and up to 2.0" in 45-75 minutes. A LOOK AHEAD: Temperatures will decrease further on Friday with highs in the 70's and lower 80's over the plains. Much like today there will be ample moisture to work with but will the cool temperatures hinder the strong storms? Regardless, scattered showers and thunderstorms are expected as early as noon Friday continuing likely into the evening with the threat for heavy rainfall that may lead to excessive runoff from stronger storms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 900 PM 0.1" (80%) to 0.4" (40%) to 0.8" (15%) MOD Arapahoe 100 PM TO 900 PM 0.1" (80%) to 0.4" (40%) to 0.8" (15%) MOD Broomfield 100 PM TO 900 PM 0.1" (80%) to 0.4" (40%) to 0.8" (15%) MOD Denver 100 PM TO 900 PM 0.1" (80%) to 0.4" (40%) to 0.8" (15%) MOD Boulder 1200 PM TO 900 PM 0.1" (80%) to 0.4" (40%) to 0.8" (15%) MOD Douglas 1200 PM TO 900 PM 0.1" (90%) to 0.4" (45%) to 0.8" (15%) MOD Jefferson 1200 PM TO 900 PM 0.1" (90%) to 0.4" (45%) to 0.8" (15%) MOD Foothills above 6500ft       Boulder 1100 AM TO 900 PM 0.1" (95%) to 0.4" (50%) to 0.8" (20%) MOD Douglas 1100 AM TO 900 PM 0.1" (95%) to 0.4" (50%) to 0.8" (20%) MOD Jefferson 1100 AM TO 900 PM 0.1" (95%) to 0.4" (50%) to 0.8" (20%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]