Flash Flood Prediction Program

Time: 551 PM Thu August 17, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- STORMS HAVE STRENGTHENED ALONG THE FOOTHILLS AND COULD MOVE INTO THE DISTRICT THIS EVENING Dew points in the District have remained in the upper 40s to low 50s which has increased the chance for some brief heavy rainfall into this evening. Storms this afternoon have not lasted off the foothills, however as we move into the evening, and we cool slightly, a better chance these storms will continue to last into the District. Generally storms will have the best chance of heavy rainfall for areas west of I-25, although a gust front from a stronger storm could have the potential to initiate additional storm storms throughout the District into the evening. The biggest threat will be a quick 0.5” in 10-15 minutes, with storms likely pulsing up and down as they slowly progress eastward. These slow storm motions, combined with dew points in the around 50 degrees has resulted in a LOW chance of Message 1s to be issued this evening. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a trace to 0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.50” total in 10-30 minutes. WORST CASE SCENARIO: A strong, stationary thunderstorm will have the potential to produce 0.50-1.00” total in under 60 minutes. A LOOK AHEAD: An overall increase in moisture in the area tomorrow will likely bring a better chance for more widespread showers and thunderstorms across the District as high temperatures remain in the 90s. Upper-level flow will shift southwesterly bringing a slight chance for stronger storm development tomorrow, especially for areas east of the I-25 corridor, which will likely result in a LOW chance for Message 1s to be issued. Conditions dry out Saturday, however a slight chance for a few high-based showers/isolated thunderstorms will remain with minimal precipitation expected at this time. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 PM THU Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Arapahoe Current TO 1000 PM THU Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Boulder Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW Broomfield Current TO 1000 PM THU Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Denver Current TO 1000 PM THU Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Douglas Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW Jefferson Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW Foothills above 6500ft       Boulder Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW Douglas Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW Jefferson Current TO 1000 PM THU Trace (60%) to 0.25" (40%) to 0.5" (20%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]