Time: 847 AM Tue September 14, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SEASONAL TEMPERATURES WITH AFTERNOON THUNDERSTORMS FAVORING AREAS SOUTH - The tail end of a disturbance is moving through the District this morning and may produce an isolated rain shower or sprinkles over the next couple hours. No meaningful precipitation is expected from the isolated morning showers. This afternoon another disturbance will move into the District and result in a chance for thunderstorms, favoring areas S and E with lesser chances N and W. - Although not all areas of the District will experience a storm today the storms that do manage to develop have the potential to become moderate to briefly strong. Relatively fast storm motions from WNW to ESE at 20-30mph will keep any heavy rainfall brief. Stronger storms may also contain gusty winds and hail. Best chances for thunderstorms today will be S of I-70 and in particular over Douglas County between noon and 6pm. Beyond 6pm conditions are expected to be drying out from W to E. - Temperatures today will be seasonal in the upper 70's to lower 80's for highs over the plains with readings about 10 degrees cooler in the foothills around 8,000ft. Normal high for Denver today is 81 degrees. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.1" of rain. Weak to moderate thunderstorms will produce rainfall rates of 0.1-0.3" in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.3-0.8" in 10-30 minutes. WORST CASE SCENARIO: A slower moving strong thunderstorm or training of strong thunderstorm cells may result in up to 1.5" of heavy rain in 45-75 minutes. A LOOK AHEAD: A stretch of dry weather will develop over the District on Wednesday and continue through the end of the week. Temperatures will be running above seasonal averages in the upper 80's to lower 90's over the plains. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1200 PM TO 600 PM Trace (40%) to 0.2" (20%) to 0.6" (10%) LOW Arapahoe 1200 PM TO 600 PM Trace (65%) to 0.2" (30%) to 0.6" (20%) LOW Boulder 1200 PM TO 600 PM Trace (40%) to 0.2" (20%) to 0.6" (10%) LOW Broomfield 1200 PM TO 600 PM Trace (40%) to 0.2" (20%) to 0.6" (10%) LOW Denver 1200 PM TO 600 PM Trace (50%) to 0.2" (25%) to 0.6" (10%) LOW Douglas 1200 PM TO 600 PM Trace (95%) to 0.2" (60%) to 0.6" (30%) MOD Jefferson 1200 PM TO 600 PM Trace (75%) to 0.2" (50%) to 0.6" (15%) LOW Foothills above 6500ft       Boulder 1200 PM TO 600 PM Trace (60%) to 0.2" (30%) to 0.6" (10%) LOW Douglas 1200 PM TO 600 PM Trace (100%) to 0.2" (65%) to 0.6" (30%) MOD Jefferson 1200 PM TO 600 PM Trace (80%) to 0.2" (50%) to 0.6" (20%) 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]