Flash Flood Prediction Program

Time: 849 AM Fri July 2, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER CHANCE FOR HEAVY RAINFALL THIS AFTERNOON AND EARLY EVENING - Not much has changed in the overall pattern over Colorado resulting in another chance for heavy rainfall this afternoon and early evening. Elevated surface moisture remains in place as dew points remain in the mid to upper 50's, with low 60's just east of the District. Once the low-level clouds have lifted, partly to mostly sunny skies will bring high temperatures into the upper 70's to low 80's. - Since we had a little fog and low-level clouds this morning, temperatures will take a little longer to peak this afternoon resulting in a later start time for storms. The first storms will initiate in the high country by midday with the best chance for foothills rain shower/thunderstorms between 1-3pm with the best chances for the plains between 3-8pm. Relatively weak steering winds from west to east between 5-10mph will result in slow moving rain showers/thunderstorms, with outflow boundaries causing nearly stationary additional storm development. This will increase the threat for heavy rainfall once again with roadways/smaller creeks and streams being prone to excessive runoff/flooding this afternoon and evening. - After 8 or 9pm the rain shower/thunderstorm activity is expected to have pushed east of the District with lingering scattered light rain showers possible into the later evening. Overnight lows will drop into the mid 50's to low 60's for the plains with low to mid 50's along the foothills. Excess surface moisture may lead to foggy conditions into Saturday morning as well. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.5" of rain in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce heavy rainfall rates of 0.5-1.5" in 10-30 minutes WORST CASE SCENARIO: Training of thunderstorm cells or a large slow moving strong thunderstorm may result in very heavy rainfall of up to 3.0" in 60-90 minutes. Should rain continue for longer than 90 minutes in duration higher amounts are possible. A LOOK AHEAD: Drier mid to upper-level air is poised to move in from from the west later this evening bringing a decrease in the heavy rain threat heading into the weekend. however, there will still be a low chance at least Saturday afternoon and early evening for rain showers/thunderstorms with the potential for heavy rainfall. Sunday will warm back into the upper 80's to low 90's with a slight chance for afternoon rain showers/isolated thunderstorms with a minimal, if any chance for heavy rainfall at this time. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Arapahoe 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Boulder 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Broomfield 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Denver 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Douglas 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Jefferson 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (25%) HIGH Foothills above 6500ft       Boulder 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (20%) HIGH Douglas 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) to 1.5" (20%) HIGH Jefferson 200 PM TO 800 PM 0.2" (75%) to 0.5" (50%) 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]