Time: 914 AM Wed May 31, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- THUNDERSTORM CHANCES INCREASE TODAY AND THE WEATHER PATTERN WILL BECOME EVEN MORE ACTIVE INTO THE UPCOMING WEEKEND Temperatures will continue to run slightly above seasonal averages with highs this afternoon in the upper 70’s to lower 80’s over the plains. Normal high for Denver today is 78 degrees. Sunny skies this morning will become mostly cloudy to cloudy at times this afternoon as storms move off the foothills and onto the plains. Thunderstorms will first develop over the foothills between noon and 1pm. Upper level steering winds from SW to NE will push the storms onto the plains between 1-3pm. Widely scattered thunderstorms will then continue likely into the evening with best chances for thunderstorms through about 9pm. After 9pm additional rain showers and possibly a weak thunderstorm will remain possible beyond midnight into the early morning hours on Thursday. Typical weak to moderate thunderstorms today will produce light to moderate rain and gusty winds. Stronger thunderstorms will be capable of producing brief heavy rainfall and may become severe with large hail and winds in excess of 50mph. A nearly stationary thunderstorm that forms along a gust front or wind convergence boundary will produce the greatest threat for an extended period of heavy rain today. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.3” of rain in 10-30 minutes. Strong thunderstorms will have the potential to produce rainfall rates of 0.3-0.8” in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 1.5” of rain in 45-75 minutes. A LOOK AHEAD: Temperatures will decrease and thunderstorm chances will increase daily from Thursday and Friday into Saturday. Thunderstorms characteristics will modify with each passing day as the threat for severe weather from stronger thunderstorms lowers while the threat for heavy rainfall and flooding increases. Saturday and Sunday appear to be the peak in the rain shower and thunderstorm activity. Precipitation may favor a soaking rain at times Saturday and Sunday versus thunderstorms as temperatures will be cool in the 60s. Should thunderstorms develop they will be very capable of producing heavy rain. Not much change in the weather pattern into next week as the onslaught of unusually wet weather continues this spring season. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Arapahoe 200 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Broomfield 200 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Denver 200 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Boulder 100 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Douglas 100 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Jefferson 100 PM TO 900 PM 0.1" (70%) to 0.3" (50%) to 0.8" (20%) MOD Foothills above 6500ft       Boulder 1200 PM TO 900 PM 0.1" (80%) to 0.3" (50%) to 0.8" (20%) MOD Douglas 1200 PM TO 900 PM 0.1" (80%) to 0.3" (50%) to 0.8" (20%) MOD Jefferson 1200 PM TO 900 PM 0.1" (80%) to 0.3" (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]