Flash Flood Prediction Program

Time: 851 AM Fri July 30, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT AGAIN TODAY WITH A CHANCE FOR AFTERNOON/EVENING/OVERNIGHT RAIN SHOWERS/ISOLATED THUNDERSTORMS - The final day of 90 degree temperatures as the pattern shifts this afternoon and into this weekend resulting in good chances for off and on rain through Sunday. Highs today will reach the low to mid 90's on the plains with mid to upper 80's along the foothills. An uptick in mid to upper-level moisture is expected this afternoon as a disturbance moves into the region bringing a good chance for scattered rain showers/isolated thunderstorms this afternoon, evening with a continued chance for some overnight rain showers into Saturday morning. - Rain showers and thunderstorms will initiate along the higher terrain this afternoon with the best chance for storms in the District between 3-5pm. Rain showers/thunderstorms chances pick up into the early evening with a continued chance for rain/thunderstorms until 10pm with generally just rain showers after 10pm and through the overnight. Storm motions will be relatively slow from W to E between 3-8mph this afternoon with the potential for stationary storms that form along outflow boundaries which will increase the threat for heavy rainfall this afternoon and evening. - The heavy rainfall threat diminishes this evening and through the overnight, however an isolated brief heavy rain showers or thunderstorm cannot be completely ruled out at this time. Overnight lows will drop into the low to mid 60's with mostly cloudy skies along with the chance for lingering rain showers through daybreak. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers to moderate thunderstorms will produce 0.10-0.40" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.4-1.2" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.4" in 60 minutes or less. A LOOK AHEAD: An active weather pattern is expected through the weekend as temperatures remain in the upper 70's to low 80's both Saturday and Sunday. The largest increase in available moisture will be on Saturday along with the highest threat for heavy rainfall. However, with cloudy skies and cooler high temperatures, there will be a chance stronger storms are unable to develop resulting in a better chance for widespread light to moderate rain showers rather than moderate to strong thunderstorms. This pattern continues Sunday with off an on rain showers/isolated thunderstorm chances throughout the day. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Arapahoe 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Boulder 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Broomfield 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Denver 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Douglas 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Jefferson 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Foothills above 6500ft       Boulder 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) HIGH Douglas 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) HIGH Jefferson 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) 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]