Flash Flood Prediction Program

Time: 945 AM Mon July 15, 2024 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Hot with a better chance for scattered showers and thunderstorms this afternoon and evening Very slight relief from the heatwave begins today as afternoon highs lose their chances of breaking triple digits. The ridge has weakened and migrated southeast, placing Colorado and the District at its top and setting up a direct moisture path between here and the Pacific. This path delivers its first moisture uptick today, and increased precipitable water values (0.7-0.8") and forecasted dewpoints in the low/mid 40s indicate that thunderstorms today are much more likely to produce measurable rainfall than the past few days. Convective initiation is expected over the high country just before noon, with storms moving off the foothills and onto the plains between 10-15mph from west to east in the following hour or two. Storms will be isolated/scattered through the afternoon and into the evening, with a slight chance for a few lingering showers into the late evening. Overnight will be mild and dry as temperatures drop into the mid to upper 60s. STORM RAINFALL POTENTIAL AND DURATION: Typical showers and isolated thunderstorms will produce a trace-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 slower moving thunderstorm may produce 0.80" total of rainfall in 30-60 minutes. A LOOK AHEAD: Flow aloft shifts from westerly to northwesterly slowly over the coming days, ushering in cooler air and stronger disturbances for storm initiation. Precipitable water values between 130-150% of normal will be present Tuesday and Wednesday, with forecast model guidance suggesting that Message issuance is likely both days associated with rounds of wetter afternoon thunderstorms in and around the District. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Arapahoe 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Boulder 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Broomfield 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Denver 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Douglas 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Jefferson 1230 PM TO 1100 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 1200 PM TO 1000 PM Trace (50%) to 0.25" (30%) to 0.5" (20%) LOW Douglas 1200 PM TO 1000 PM Trace (50%) to 0.25" (30%) to 0.5" (20%) LOW Jefferson 1200 PM TO 1000 PM Trace (50%) to 0.25" (30%) 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]