Time: 845 AM Sun September 3, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM TODAY WITH A CHANCE OF WIDESPREAD AFTERNOON/EVE SHOWERS & THUNDERSTORMS An approaching disturbance from the west will start to make its way through Colorado today leading to a good chance for widespread showers and thunderstorms this afternoon and into this evening. High temperature today will reach the upper 80s to low 90s this afternoon. Storms likely initiate along the higher terrain by midday and will move out onto the plains between 1-3pm. There is a chance for multiple rounds of storms today with storm chances tapering off by 9pm. A low chance of storms become severe today, mainly for gusty winds and hail up to 1” in diameter, favoring areas east of I-25. Typical storm motions will be SW to NE around 10mph, with some erratic storm motions possible due to storms forming along outflow boundaries. These outflow storms will likely have the biggest threat for moderate to heavy rainfall as they remain stationary at times. A quick 0.5” in 10-15 minutes will likely be the main concern, however a stalled-out storm could produce isolated higher amounts. STORM RAINFALL POTENTIAL AND DURATION: Typical showers and weak thunderstorms will produce rainfall of a 0.05” to 0.25” total in 10-30 minutes. Moderate to strong showers and thunderstorms Will produce rainfall of 0.25” to 0.75” total in 10-30 minutes. WORST CASE SCENARIO: Strong stationary, or training of thunderstorms has the potential to produce 0.75” to 1.50” in under 60 minutes. A LOOK AHEAD: This disturbance starts to move into Wyoming overnight tonight. This will keep storm chances in place for the District tomorrow afternoon and evening, however the threat of heavy rainfall should be minimal at best. Best chance for storms tomorrow will be between 2-7pm with skies clearing out quickly in the evening hours. Conditions start to dry out Tuesday behind a cold front that will drop high temperatures back into the upper 70s to low 80s. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Arapahoe 200 PM TO 900 PM 0.05" (70%) to 0.25" (40%) to 0.75" (20%) MOD Boulder 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Broomfield 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Denver 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Douglas 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Jefferson 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Foothills above 6500ft       Boulder 200 PM TO 900 PM 0.05" (90%) to 0.25" (70%) to 0.75" (50%) MOD Douglas 200 PM TO 900 PM 0.05" (80%) to 0.25" (60%) to 0.75" (30%) MOD Jefferson 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) 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]