Flash Flood Prediction Program

Time: 834 AM Thu June 17, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- RECORD BREAKING HEAT ONCE AGAIN WITH A CHANCE FOR HIGH-BASED AFTERNOON RAIN/ISOLATED THUNDERSTORMS - The heat wave continues for one more day as high temperatures reach the upper 90's to low triple digits again this afternoon. Overnight lows remained in the mid to upper 60s for most areas in the District with temperatures already closing in on 80 degrees this morning. - Similar conditions as yesterday with a very slight chance for a few high-based rain showers/isolated thunderstorms, however most rainfall will struggle to reach the surface today with the main threat likely being gusty winds and a few lightning strikes. Storm motions will be from the W to E between 5-15mph. If a stronger, slower moving storm is able to develop rainfall rates could reach the 0.1-0.3" range, although chances are unlikely that will occur. Storms will initiate along the higher terrain around midday with the best storm chances for the District between 2-8pm this afternoon. - After 8pm, skies will gradually clear this evening with overnight lows dropping into the 60's for the plains with upper 50's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical high-based rain showers/isolated thunderstorms will produce between a trace-0.1" of rainfall in 10-30 minutes. A moderate rain shower/thunderstorm is capable of producing 0.1-0.3" in 10-30 minutes. WORST CASE SCENARIO: Anchored thunderstorms along the foothills, or a thunderstorm that forms along an outflow boundary has the potential to produce 0.3-0.8" in 60-90 minutes. A LOOK AHEAD: A reprieve from triple digit high temperatures tomorrow as a cold front moves through the region overnight tonight. Temperatures tomorrow will reach the upper 80's to low 90's on the plains with a better chance for afternoon and evening rain/isolated thunderstorms as upper-level moisture increases over the region. This pattern will hold through the weekend with temperatures remaining in the upper 80's to low 90's Saturday and Sunday with rain/isolated thunderstorm chances for both days with Saturday having the most potential for heavy rainfall at this time. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Arapahoe 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Boulder 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Broomfield 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Denver 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Douglas 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Jefferson 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (5%) NONE Foothills above 6500ft       Boulder 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (10%) NONE Douglas 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (10%) NONE Jefferson 200 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.3" (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]