Flash Flood Prediction Program

Time: 859 AM Sun May 28, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- NEAR NORMAL TEMPERATURES WITH A REDUCTION IN THUNDERSTORM ACTIVITY EXPECTED TODAY Temperatures will be at or slightly above normal over the District today with afternoon highs in the upper 70s to around 80 degrees. The normal high for Denver today is 77 degrees. A reduction in thunderstorm activity is expected today compared to previous days with isolated afternoon thunderstorms. Overall, there is a decrease in moisture at the surface and aloft which will result in typical storms only producing light to briefly moderate rain. There is a low chance of a stronger storm should a moisture boundary push back to the W during the afternoon. Should a stronger storm be able to develop brief heavy rain will be possible as well as more hail. Storms that develop today will move from WSW to ENE at around 20mph. The relatively fast storm motions will also help to reduce point rainfall amounts today. The best chances for thunderstorms will be between 1-8pm. Thunderstorms will initialize over the foothills first then move onto the plains after 2pm with some areas likely missing out on storm activity today. After 8 or 9pm conditions are expected to dry out for the remainder of the evening and overnight period. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.1” of rain. Moderate to briefly strong thunderstorms will have the potential to produce rainfall rates of 0.1-0.4” in 10-30 minutes. WORST CASE SCENARIO: A strong, slower moving thunderstorm may result in rainfall rates of 0.3-0.7” in 10-30 minutes and up to 1.0” in 45-60 minutes. A LOOK AHEAD: Similar setup on Monday with isolated afternoon and evening thunderstorms with typical storms producing light to briefly moderate rain. A stronger storm cannot be completely ruled out. Temperatures Monday will climb to above normal with highs in the lower 80’s over the plains. Thunderstorm activity will begin to increase Tuesday and increase further on Wednesday and Thursday with better chances for stronger storms capable of producing heavy rainfall and possibly severe weather. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 800 PM Trace (60%) to 0.2" (30%) to 0.4" (15%) LOW Arapahoe 200 PM TO 800 PM Trace (60%) to 0.2" (30%) to 0.4" (15%) LOW Broomfield 200 PM TO 800 PM Trace (60%) to 0.2" (30%) to 0.4" (15%) LOW Denver 200 PM TO 800 PM Trace (60%) to 0.2" (30%) to 0.4" (15%) LOW Boulder 130 PM TO 800 PM Trace (70%) to 0.2" (35%) to 0.4" (15%) LOW Douglas 130 PM TO 800 PM Trace (75%) to 0.2" (35%) to 0.4" (15%) LOW Jefferson 130 PM TO 800 PM Trace (70%) to 0.2" (35%) to 0.4" (15%) LOW Foothills above 6500ft       Boulder 100 PM TO 800 PM Trace (80%) to 0.2" (40%) to 0.4" (20%) LOW Douglas 100 PM TO 800 PM Trace (80%) to 0.2" (40%) to 0.4" (20%) LOW Jefferson 100 PM TO 800 PM Trace (80%) to 0.2" (40%) to 0.4" (20%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]