Flash Flood Prediction Program

Time: 849 AM Thu June 24, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH A GOOD CHANCE FOR AFTERNOON/EVENING RAIN SHOWERS/ISOLATED THUNDERSTORMS - A weak disturbance moved through early this morning bringing very light rain showers for central and eastern portions of the District. Shower activity has moved eastward leaving mostly cloudy skies before afternoon temperatures reach the mid to upper 80's for the plains with upper 70's to around 80 along the foothills. A good chance this afternoon for rain/isolated thunderstorms with a slight chance for severe weather with gusty winds, hail up to 1", also including brief heavy rainfall favoring areas east of I-25 at this time. - Storms will initiate along the Palmer Divide by midday today with the best chance for rain showers/isolated thunderstorms in the District between 2-8pm. A couple rounds of storms are possible today, with the first round having the most potential for heavy rainfall. Storm motions will be fairly brisk between 10-15mph helping limit point rainfall amounts, although a slower moving storm, formed off an outflow boundary does have the potential for brief heavy rain. Storm intensities will start to decrease after 8pm, although rain showers or an isolated thunderstorm could be possible through midnight before chances finally taper off heading into the overnight. - Skies gradually clear after midnight as overnight lows drop into the upper 50's to low 60's along the plains with low to mid 50's in the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/thunderstorms will produce a TR-0.3" in 10-30 minutes. A moderate to strong thunderstorm will produce 0.3-0.5" in 10-30 minutes. WORST CASE SCENARIO: An anchored thunderstorm, or a stationary thunderstorm formed off an outflow boundary has the potential to produce 0.5-1.0" in 30-60 minutes. A LOOK AHEAD: An active weather pattern holds over the next several days as a slow-moving low pressure system moves from the SW makes its way through the region resulting in a good chance for rain/thunderstorms into the weekend. Friday will be slightly cooler as a cold front moves through overnight bringing highs into the low to mid 70's. A good chance Friday afternoon and evening for rain showers and thunderstorms with a good chance for some of those storms to become severe. Similar conditions Saturday as high temperatures remain in the low 70's with a continued chance for rain/thunderstorms off and on throughout the day. Sunday starts to dry out a bit, although with residual moisture in place and some upper-level support there will be another chance for rain showers/thunderstorms Sunday afternoon and evening. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 800 PM Trace (75%) to 0.3" (40%) to 0.5" (20%) LOW Arapahoe 100 PM TO 800 PM Trace (75%) to 0.3" (40%) to 0.5" (20%) LOW Boulder 100 PM TO 800 PM Trace (75%) to 0.3" (30%) to 0.5" (10%) LOW Broomfield 100 PM TO 800 PM Trace (75%) to 0.3" (30%) to 0.5" (10%) LOW Denver 100 PM TO 800 PM Trace (75%) to 0.3" (40%) to 0.5" (20%) LOW Douglas 100 PM TO 800 PM Trace (75%) to 0.3" (40%) to 0.5" (20%) LOW Jefferson 100 PM TO 800 PM Trace (75%) to 0.3" (30%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 1200 PM TO 800 PM Trace (75%) to 0.3" (30%) to 0.5" (10%) LOW Douglas 1200 PM TO 800 PM Trace (75%) to 0.3" (40%) to 0.5" (20%) LOW Jefferson 1200 PM TO 800 PM Trace (75%) to 0.3" (30%) to 0.5" (10%) 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]