Flash Flood Prediction Program

Time: 846 AM Thu July 29, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER HOT DAY WITH A SLIGHT CHANCE FOR SCATTERED HIGH-BASED AFTERNOON RAIN SHOWERS/ISOLATED THUNDERSTORMS - After record breaking heat yesterday, very little change in the forecast today with highs expected in the low to mid 90s this afternoon. Although minimal, a slightly better chance today for scattered high-based afternoon/early evening rain showers/isolated thunderstorms. However, Most areas will likely remain dry today, with any storm development favoring areas along the Palmer Divide and eastward out on the plains. - Best chance for storm development will begin between 2-4pm with a chance for rain showers/isolated thunderstorms through 7-9pm with a slight chance for continued rain showers favoring northern portions of the District at this time. Most rain showers/isolated thunderstorms will be high-based if they do develop, resulting in a better chance for gusty winds and the occasional lightning strike, however, current dewpoints are in the low to mid 50's for eastern portions of the District. If these dewpoints struggle to mix out during the day, a threat will remain for isolated moderate to heavy rainfall if a stronger storm is able to develop, especially off an outflow boundary resulting in erratic or stationary storm movement. - Any threat for stronger rain showers/isolated thunderstorms diminishes quickly after sunset with generally mild conditions overnight and into Friday as lows are expected to reach the upper 60's to low 70's for the plains with low to mid 60's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical high-based rain showers/isolated thunderstorms will produce a TR-0.10" in 10-30 minutes. A moderate rain shower/isolated thunderstorm will produce 0.1-0.3" in 10-30 minutes. WORST CASE SCENARIO: A stronger thunderstorm that forms along an outflow boundary will have the potential to produce 1.2" in less than 60 minutes. A LOOK AHEAD: Monsoonal moisture returns Friday afternoon with a good chance for rain showers/thunderstorms over the District during the afternoon/evening and through the overnight into Saturday. As this disturbance slowly churns, rain and thunderstorm chances will continue over the region through the entire weekend before this disturbance starts to move eastward. With adequate moisture in place at the surface and in the mid to upper-level, the threat for heavy rainfall will likely persist through the weekend before the region starts to dry out on Monday of next week. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) LOW Arapahoe 200 PM TO 900 PM Trace (35%) to 0.2" (20%) to 0.3" (15%) LOW Boulder 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Broomfield 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Denver 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) LOW Douglas 200 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.3" (15%) LOW Jefferson 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Foothills above 6500ft       Boulder 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) NONE Douglas 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) NONE Jefferson 200 PM TO 900 PM Trace (30%) to 0.2" (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]