Flash Flood Prediction Program

Time: 1028 AM Fri August 27, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SUNNY AND MILD TO START THE DAY WITH CHANCE FOR SCATTERED AFTERNOON RAIN SHOWERS/THUNDERSTORMS - A relatively mild start to the day as high temperatures reach the upper 80's to low 90's this afternoon. There is a chance for afternoon to evening rain showers and thunderstorms across the Front Range Urban Corridor ahead of tomorrow morning’s frontal passage. Storms are expected roll off the higher terrain by mid-afternoon, moving in an east-northeast direction. - Storms are expected to initiate along the higher terrain by mid-day, with storms rolling off the foothills by mid-afternoon. Prime time for storms today will be from 3pm to 9pm. Storm potential will decrease throughout the evening, becoming calm overnight. Storm motions will be from the W/SW to E/NE between 10-15mph which will help limit point rainfall amounts, however a slower moving storm formed off an outflow cannot be completely ruled out at this time. - Dew points across The District are currently in the mid to upper 40's. Dew points are expected to drop into the upper 30 low 40s throughout the day, however if dew points do not mix out, the potential for moderate to brief heavy rainfall will increase. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/thunderstorms will produce between a Trace-0.2" in 10-30 minutes. A moderate rain shower/thunderstorm will produce 0.2-0.4" in 10-30 minutes. WORST CASE SCENARIO: A moderate to strong thunderstorm formed off an outflow boundary has the potential to produce 1" of rainfall in 30-60 minutes. A LOOK AHEAD: The approaching cool front will sweep across the plains from the north early tomorrow morning, lowering weekend high temperatures into the mid to upper 80s Saturday, and low to mid 80s on Sunday. This front also brings a chance of isolated evening showers on Saturday and Sunday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.4" (5%) NONE Arapahoe 300 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.4" (5%) NONE Boulder 300 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.4" (5%) NONE Broomfield 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Denver 300 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.4" (5%) NONE Douglas 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Jefferson 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Foothills above 6500ft       Boulder 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Douglas 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Jefferson 300 PM TO 900 PM Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]