Flash Flood Prediction Program

Time: 916 AM Wed July 5, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- THUNDERSTORM STRENGTH/COVERAGE WILL HINGE UPON DAYTIME HEATING Temperatures will be well below normal today with afternoon highs reaching the mid 60’s to around 70 over the plains. Normal high for Denver today is 89 degrees. The temperatures will be held down due to cloud cover with the foothills and Palmer Divide breaking out of the clouds quicker than the majority of the plains. The day will start off relatively quiet with thunderstorm chances this afternoon hinging upon how much sunshine is able to develop. Should conditions stay on the cloudy/cooler side the chances for thunderstorms will be low and the storms relatively weak. If clouds break up and there is more daytime heating, then thunderstorms will be more numerous/stronger. With more sunshine expected over the foothills and Palmer Divide today these areas will be more prone for thunderstorm activity, some of which may become strong with the potential for heavy rainfall and hail. Rain showers and isolated to widely scattered thunderstorms will first develop over the higher terrain to the S and W of the District between noon and 2pm. Chances for thunderstorms then spread out onto the plains after 2pm and continue possible until around midnight. Storms that develop in the evening have the potential to be the stronger storms of the day. Showers and thunderstorms that develop today will be relatively fast moving from W to E at 20-25mph which will help to reduce point rainfall amounts over a single location. A large thunderstorm or training of thunderstorm cells will pose the greatest risk for extended periods of heavy rainfall that may lead to excessive runoff. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.5” of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.5” in 10-30 minutes. WORST CASE SCENARIO: A large thunderstorm or training of thunderstorm cells may result in up to 2.3” of rain in 45-75 minutes. A LOOK AHEAD: Temperatures will warm back into the 80’s over the plains on Thursday with widely scattered afternoon thunderstorms, some of which will contain brief heavy rainfall. Daily chances for afternoon/evening thunderstorms will continue Friday and Saturday with temperatures around 80 for highs over the plains. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1159 PM 0.1" (80%) to 0.5" (40%) to 1.5" (10%) MOD Arapahoe 200 PM TO 1159 PM 0.1" (80%) to 0.5" (40%) to 1.5" (10%) MOD Broomfield 200 PM TO 1159 PM 0.1" (80%) to 0.5" (40%) to 1.5" (10%) MOD Denver 200 PM TO 1159 PM 0.1" (80%) to 0.5" (40%) to 1.5" (10%) MOD Boulder 100 PM TO 1159 PM 0.1" (80%) to 0.5" (50%) to 1.5" (15%) MOD Douglas 100 PM TO 1159 PM 0.1" (80%) to 0.5" (50%) to 1.5" (15%) MOD Jefferson 100 PM TO 1159 PM 0.1" (80%) to 0.5" (50%) to 1.5" (15%) MOD Foothills above 6500ft       Boulder 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH Douglas 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH Jefferson 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]