Flash Flood Prediction Program

Time: 927 AM Sun June 11, 2023 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER TOUND OF SLOW-MOVING THUNDERSTORMS EXPECTED THIS AFTERNOON A blocking pattern is in place over the continental US, positioning southwesterly upper-level flow across Colorado while mid-level anti cyclonic flow continues to transport moisture into eastern Colorado. This morning will be mostly cloudy across the District followed by afternoon temperatures in the upper 60s to low 70s and dew points in the low 50s. Forecast soundings reveal bulk shear around 30 kt, and PWAT values between 0.75” to 0.85”. These conditions will support an unstable environment favoring persistent clustered thunderstorms by the mid to late afternoon. Storms are expected to exit the District by the late evening hours. STORM RAINFALL POTENTIAL AND DURATION: Typical thunderstorms have the potential to produce moderate to heavy rainfall of 0.4” to 0.75” in 10 to 30 minutes. Strong thunderstorms have the potential to produce moderate to heavy rainfall of 0.75” to 1.50” in 10 to 30 minutes. WORST CASE SCENARIO: Anchored or slow-moving thunderstorms have the potential to produce 1.50” to 2.25” in 30 to 60 minutes. A LOOK AHEAD: Tomorrow will be similar with temperatures in the upper 60s to low 70s and scattered to widespread clustered severe thunderstorms and heavy rain across the Front Range Urban Corridor. Looking ahead, the upper-level pattern will finally exit the region mid-week, followed by a more seasonal pattern of isolated afternoon showers and thunderstorms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Arapahoe 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Boulder 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Broomfield 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Denver 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Douglas 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Jefferson 300 PM TO 1000 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Foothills above 6500ft       Boulder 100 PM TO 800 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Douglas 100 PM TO 800 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH Jefferson 100 PM TO 800 PM 0.4" (90%) to 0.75" (50%) to 1.5" (25%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]