Flash Flood Prediction Program

Time: 933 AM Mon July 1, 2024 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Cool and cloudy to start the day with another chance for isolated showers and thunderstorms this afternoon and evening. Southwesterly upper-level flow aloft continues to dominate the region today as a ridge of high-pressure churns of the southern US. This will keep similar conditions in place over the District with another chance for isolated afternoon and evening showers and thunderstorms. Once again, most activity will be hit or miss across the I-25 corridor with some areas likely ending up dry. Elevated dew points at the surface currently, in the mid 50s to around 60 degrees will keep chances for moderate to heavy rainfall out of any storms that do develop. A very slight chance of storms become severe with gusts up to 60mph and hail up to 1.0” in diameter. The best chance for showers and thunderstorms will be between 11am-9pm with a few lingering showers possible overnight. Storm motions will be from the W/SW to E/NE between 10-20mph which will likely help limit point rainfall amounts, although stronger storms could produce outflow boundaries. These outflow boundaries have the potential to produce erratic storm motions leading to a better chance of longer lasting moderate to heavy rainfall. The largest threat will be a quick 0.50” in 10-30 minutes, however, with these elevated dew points, stationary storms could produce 0.50-1.25” in under 30 minutes today. Storm intensities will decrease after sunset with typical off and on showers possible through the overnight. Overnight temperatures will dip back into the low 60s for the Metro area with upper 50s along the foothill regions. 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 strong, stationary thunderstorm, or training of thunderstorm cells will have the potential to produce up to 1.25” total in under 30 minutes. A LOOK AHEAD: Tomorrow will start to dry out at the surface with more typical dew points in the upper 30s to low 40s in the afternoon. A slight chance for afternoon showers and isolated thunderstorms will be possible, although with decreased dew points, high-based storms will be possible with minimal rainfall expected at this time. Wednesday will be similar with another chance for high-based afternoon and evening showers/isolated thunderstorms with minimal precipitation as most struggle to reach the surface during peak daytime heating. This will likely result in gusty sprinkles rather than any meaningful rainfall during the daytime hours with a slightly better chance for impactful rainfall during the late evening. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1100 AM TO 1159 PM Trace (65%) to 0.25" (35%) to 0.5" (20%) LOW Arapahoe 1100 AM TO 1159 PM Trace (65%) to 0.25" (35%) to 0.5" (20%) LOW Boulder 1100 AM TO 1159 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Broomfield 1100 AM TO 1159 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Denver 1100 AM TO 1159 PM Trace (65%) to 0.25" (35%) to 0.5" (20%) LOW Douglas 1100 AM TO 1159 PM Trace (70%) to 0.25" (40%) to 0.5" (25%) LOW Jefferson 1100 AM TO 1159 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Foothills above 6500ft       Boulder 1100 AM TO 1159 PM Trace (75%) to 0.25" (50%) to 0.5" (25%) LOW Douglas 1100 AM TO 1159 PM Trace (75%) to 0.25" (50%) to 0.5" (25%) LOW Jefferson 1100 AM TO 1159 PM Trace (75%) to 0.25" (50%) to 0.5" (25%) 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]