Time: 901 AM Thu July 6, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARMER WITH AFTERNOON/EVENING THUNDERSTORMS PRODUCING BRIEF HEAVY RAINFALL AND SEVERE WEATHER The low clouds and fog from earlier this morning is burning off quickly and with more sunshine today temperatures will warm into the 70’s over the District. Normal high for Denver today is 89 degrees. The additional heating and abundant surface moisture in place will result in stronger thunderstorms today in and around the District. Thunderstorms will first develop over the foothills between noon and 1pm, then move onto the plains between 1-3pm. Chances for thunderstorms are expected to continue well into the evening with multiple rounds of storms possible. Prime time for thunderstorms is from 2pm-midnight. Additional rain showers will continue possible beyond midnight with conditions drying out overnight. Stronger storms that develop today will have the potential to produce brief heavy rainfall and become severe with large hail and possibly a very isolated tornado. Typical storms will move from W to E or NNW to ESE at 20-30mph with stronger storms possibly moving more slowly/erratically. Fast storm motions will help to reduce point rainfall amounts but a large thunderstorm or training of thunderstorm cells could produce extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. Message 1’s will likely be issued by early afternoon and continue well into the evening. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.5” of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.5” in 10-30 minutes. WORST CASE SCENARIO: A slower moving large thunderstorm or training of thunderstorm cells may result in up to 2.2” of rain in 45-60 minutes. A LOOK AHEAD: A couple more active thunderstorm days are expected on Friday and Saturday then chances for thunderstorms decrease Sunday and Monday may end up being on the drier side. Storms that develop Friday and Saturday will continue to have the potential to become strong/severe with brief heavy rainfall and hail. Temperatures will be running either side of 80 degrees for afternoon highs over the plains. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1159 PM 0.1" (90%) to 0.5" (50%) to 1.5" (25%) HIGH Arapahoe 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Broomfield 200 PM TO 1159 PM 0.1" (90%) to 0.5" (50%) to 1.5" (25%) HIGH Denver 200 PM TO 1159 PM 0.1" (90%) to 0.5" (50%) to 1.5" (25%) HIGH Boulder 100 PM TO 1159 PM 0.1" (90%) to 0.5" (50%) to 1.5" (25%) HIGH Douglas 100 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Jefferson 100 PM TO 1159 PM 0.1" (90%) to 0.5" (50%) to 1.5" (25%) HIGH Foothills above 6500ft       Boulder 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Douglas 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) HIGH Jefferson 1200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) 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]