Time: 1021 AM Thu June 22, 2023 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER ROUND OF SLOW-MOVING THUNDERSTORMS EXPECTED ACROSS THE DISTRICT TODAY Another active weather day is expected as multiple ingredients for heavy rainfall come together across the district. Strong southwesterly upper-level flow across Colorado will support an environment for another active day of showers and thunderstorms in the district. Daytime heating will create an unstable environment favoring widespread clustered thunderstorms by the mid to late afternoon. High temperatures will reach the mid to upper 70s with dew points in the low to mid 50s. Low level moisture remains elevated from widespread heavy rain yesterday. Precipitable water (PWAT) values have decreased some, though look to be in the 0.70-0.80” range today. This combination will result in storms with the potential for locally heavy rainfall. Message 2 will be issued by noon as a flash flood watch has been issued by the NWS for the entire District from noon through midnight. Storms are expected to exit the Front Range Urban Corridor by the late evening hours. STORM RAINFALL POTENTIAL AND DURATION: Typical thunderstorms have the potential to produce moderate to heavy rainfall of 0.50” to 1.00” in 10-30 minutes. Strong thunderstorms have the potential to produce very heavy rainfall of 1.00” to 1.50” in 10-30 minutes. WORST CASE SCENARIO: Anchored or slow-moving thunderstorms have the potential to produce 1.50” to 2.20” in 45 to 60 minutes. A LOOK AHEAD: Looking ahead, the upper-level pattern will exit the region overnight, followed by a period of high-pressure ridging, sunny skies, and dry conditions. Tomorrow will be mostly sunny with afternoon highs in the mid to upper 80s. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Arapahoe 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Boulder 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Broomfield 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Denver 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Douglas 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Jefferson 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Foothills above 6500ft       Boulder 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Douglas 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) HIGH Jefferson 200 PM TO 1000 PM 0.5" (90%) to 1" (60%) to 1.5" (30%) 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]