Flash Flood Prediction Program

Time: 841 AM Mon September 11, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOL, FALL LIKE WEATHER TODAY, WITH A CHANCE FOR OFF AND ON SHOWERS THROUGH THIS EVENING Upper-level winds will shift from westerly to northwesterly throughout the day today. This will provide a slight chance for a few showers and possibly an isolated thunderstorm or two this afternoon. Temperatures today will remain cooler with highs in the low to mid 60s across the District. These cooler temperatures will likely limit storm potential today, resulting in mostly off and on showers this morning and through the afternoon with rainfall chances tapering off this evening. Due to elevated moisture, both at the surface and aloft, some showers could be efficient rain producers today. Typical showers will produce 0.05-0.25” of rainfall in 10-30 minutes, however a stronger shower or isolated thunderstorm will have the potential to produce moderate to heavy rainfall with 0.25-0.75” in 10-30 minutes possible. The best chance for any isolated thunderstorms will be between noon-6pm favoring areas along the foothills at this time. This will keep a LOW chance for Message 1s to be issued this afternoon. This evening, skies will be partly cloudy with dry conditions expected through the overnight. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce 0.05 to 0.25” total in 10-30 minutes. Moderate to strong showers have the potential to 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: Tomorrow will likely have the least chance for rainfall/isolated thunderstorms in the District as temperatures start to increase to a more seasonable low to mid 70s. A better chance for rain showers and thunderstorms Wednesday afternoon and early evening as high temperatures reach the mid to upper 70s. A good chance for some isolated moderate to heavy rainfall Wednesday. Similar conditions remain in place Thursday with another good chance for showers/thunderstorms across the District with at least a slight chance for moderate to heavy rainfall. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 600 PM MON 0.05" (60%) to 0.25" (30%) to 0.75" (10%) LOW Arapahoe Current TO 600 PM MON 0.05" (60%) to 0.25" (30%) to 0.75" (10%) LOW Boulder Current TO 600 PM MON 0.05" (60%) to 0.25" (30%) to 0.75" (10%) LOW Broomfield Current TO 600 PM MON 0.05" (60%) to 0.25" (30%) to 0.75" (10%) LOW Denver Current TO 600 PM MON 0.05" (60%) to 0.25" (30%) to 0.75" (10%) LOW Douglas Current TO 600 PM MON 0.05" (70%) to 0.25" (40%) to 0.75" (10%) LOW Jefferson Current TO 600 PM MON 0.05" (70%) to 0.25" (40%) to 0.75" (10%) LOW Foothills above 6500ft       Boulder Current TO 600 PM MON 0.05" (70%) to 0.25" (35%) to 0.75" (15%) MOD Douglas Current TO 600 PM MON 0.05" (75%) to 0.25" (40%) to 0.75" (15%) MOD Jefferson Current TO 600 PM MON 0.05" (70%) to 0.25" (35%) to 0.75" (15%) 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]