Flash Flood Prediction Program

Time: 857 AM Fri July 7, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- BELOW NORMAL TEMPERATURES WITH WIDELY SCATTERED AFTERNOON/EVENING THUNDERSTORMS A weak cold front moved through this morning and will keep temperatures below normal once again with highs in the mid 70’s to around 80 over the plains with 60’s and 70’s in the Front Range foothills. Normal high for Denver today is 89 degrees. Slightly drier air has intruded behind the cold front this morning with surface dew points lowering into the upper 40’s to lower 50’s. The decrease in surface moisture will reduce the severity of storms today and lower the heavy rainfall threat but not eliminate it. Thunderstorms will develop over the foothills by around noon and then push eastward onto the I-25 corridor between 1-3pm. Best chances for widely scattered thunderstorms will be between 2-9pm. Strong thunderstorms will have the potential to produce brief heavy rainfall, hail and gusty winds. After 9pm conditions expected to dry out for the remainder of the evening and overnight period. Thunderstorms that develop today will be fast moving from W to E or WNW to ESE at 20-30mph which will help to lower point rainfall amounts and keep heavy rainfall brief for the most part. Thunderstorms that form along surface wind convergence/outflow boundaries may move more slowly/erratically and training of thunderstorm cells could result in extended periods of moderate to heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4” of rain. Moderate to strong thunderstorms will have the potential to produce 0.4-1.0” in 10-30 minutes. WORST CASE SCENARIO: Slower moving thunderstorms or training of thunderstorm cells may result in up to 1.8” of rain in 45-60 minutes. A LOOK AHEAD: Saturday will continue to feature a good chance for afternoon/evening thunderstorms with the potential for heavy rainfall. Temperatures will remain on the cool side with highs in the 70’s to around 80 over the plains. A warmer and drier weather pattern will begin to unfold on Sunday and continue through next week with conditions feeling more like summer. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Arapahoe 200 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Broomfield 200 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Denver 200 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Boulder 100 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Douglas 100 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Jefferson 100 PM TO 900 PM 0.1" (75%) to 0.4" (50%) to 1" (15%) MOD Foothills above 6500ft       Boulder 1200 PM TO 900 PM 0.1" (85%) to 0.4" (50%) to 1" (15%) MOD Douglas 1200 PM TO 900 PM 0.1" (85%) to 0.4" (50%) to 1" (15%) MOD Jefferson 1200 PM TO 900 PM 0.1" (85%) to 0.4" (50%) to 1" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]