Flash Flood Prediction Program

Time: 152 PM Sat June 18, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SHOWERS AND THUNDERSTORMS TO IMPACT THE DISTRICT INTO THE EVENING/HEAVY RAINFALL THREAT LOWERING - Temperatures have reached the upper 80's to lower 90's over the plains as of 1:45 PM with abundant moisture in the mid and upper levels being imported from the south. At the surface, moisture levels have backed off with dew points currently ranging from the upper 30's to mid 40's. Due to the decrease in surface moisture from this morning the threat for heavy rainfall is lower but not completely eliminated. Storms are just now beginning to develop over southern and western areas of the District over Douglas and Jefferson Counties. - Fast individual storm motions from SSW to NNE at around 25mph will keep the storms that develop today moving along at a rapid pace reducing point rainfall amounts from a single storm. Most storms will produce light to briefly moderate rain and gusty winds. A stronger thunderstorm cannot be ruled out but chances have decreased. Training of thunderstorm cells may create an opportunity for longer durations of moderate to briefly heavy rainfall. - 1-3 rounds of showers and thunderstorms are expected into the evening. Best chances for thunderstorms will be through 9 or 10pm. Beyond 10pm any shower activity will be light in nature with minimal accumulation. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" 10-30 minutes. Moderate to briefly strong thunderstorms will have the potential to produce rainfall rates of 0.2-0.5" in 10-30 minutes. WORST CASE SCENARIO: Training of thunderstorm cells may result in up to 1.0" of rainfall in 45-75 minutes. A LOOK AHEAD: Another active day on Sunday with monsoon moisture impacting the District leading to scattered afternoon and evening thunderstorms. Storm motions will be relatively fast leading to the potential for brief bouts of moderate/heavy rainfall. Temperatures will continue to retreat with highs in the 80's to around 90 over the plains. Conditions dry out on Monday but temperatures remain in the 80s to around 90 for afternoon highs. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1000 PM Trace (80%) to 0.2" (40%) to 0.5" (10%) LOW Arapahoe 200 PM TO 1000 PM Trace (80%) to 0.2" (40%) to 0.5" (10%) LOW Broomfield 200 PM TO 1000 PM Trace (80%) to 0.2" (40%) to 0.5" (10%) LOW Denver 200 PM TO 1000 PM Trace (80%) to 0.2" (40%) to 0.5" (10%) LOW Boulder Current TO 1000 PM SAT Trace (90%) to 0.2" (50%) to 0.5" (15%) LOW Douglas Current TO 1000 PM SAT Trace (90%) to 0.2" (50%) to 0.5" (15%) LOW Jefferson Current TO 1000 PM SAT Trace (90%) to 0.2" (50%) to 0.5" (15%) LOW Foothills above 6500ft       Boulder Current TO 1000 PM SAT Trace (95%) to 0.2" (75%) to 0.5" (20%) LOW Douglas Current TO 1000 PM SAT Trace (95%) to 0.2" (75%) to 0.5" (20%) LOW Jefferson Current TO 1000 PM SAT Trace (95%) to 0.2" (75%) 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]