Time: 943 AM Sun September 10, 2023 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SCATTERED TO WIDESPREAD SHOWERS AND THUNDERSTORMS TODAY AND TONIGHT An upper-level disturbance and its associated cold front swept across the area last night, supporting an unsettled weather pattern and much cooler temperatures this week. Today will be mostly cloudy with high temperatures in the upper 60s to low 70s, dew points in the low 50s, followed by scattered to widespread showers and thunderstorms. Storm activity will gradually increase through the early afternoon and into the evening hours. A strong upper-level jet will support the potential for clustered thunderstorms. However, quick storm motions around 25-30 mph will help limit point rainfall amounts. Cooler temperatures this evening will favor stratified rainfall which may persist overnight. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce moderate rainfall of up to 0.50” total in 10-30 minutes. A strong thunderstorm has the potential to produce heavy rainfall up to 0.75” total in 10-30 minutes. WORST CASE SCENARIO: A training thunderstorm has the potential to produce 0.75”-1.25” total rainfall 45-60 minutes. A LOOK AHEAD: A similar pattern is expected tomorrow. High temperatures will reach the mid to upper 60s with overcast showery conditions. Scattered to widespread showers will continue into the overnight hours with a slight chance for a few rumbles of thunder. There is still some uncertainty about details and timing for the remainder of the week, which will depend on the track of this system. We will continue to monitor this storm as it develops over the coming days. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Arapahoe 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Boulder 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Broomfield 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Denver 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Douglas 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Jefferson 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Foothills above 6500ft       Boulder 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Douglas 400 PM TO 1000 PM 0.25" (75%) to 0.5" (50%) to 0.75" (25%) MOD Jefferson 400 PM TO 1000 PM 0.25" (75%) to 0.5" (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]