Flash Flood Prediction Program

Time: 745 PM Fri September 2, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- THUNDERSTORMS TO IMPACT PORTIONS OF THE DISTRICT THIS EVENING/MESSAGE 1'S MAY BE ISSUED SHORTLY - Thunderstorms have developed over Larimer and Weld Counties and are moving southeastward and will likely impact portions of the District into the evening. These storms are relatively fast moving and and high-based resulting in gusty winds and light to moderate rain from the typical storms. - A stronger slow moving thunderstorm will be able to moisten the air underneath and will be capable of producing brief heavy rainfall which may result in Message 1's being issued shortly. - Prime time for thunderstorm activity will be from 9pm until around midnight. Best chances for stronger storms will be along and E of I-25 with lesser chances for strong storms over the foothills. Thunderstorms may also contain hail and gusty winds in excess of 40mph. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.1-0.4" in 10-30 minutes. Strong thunderstorms will have the potential to produce brief heavy rainfall of 0.3-0.8" in 10-30 minutes. WORST CASE SCENARIO: Training of thunderstorm cells or a slower moving strong thunderstorm will have the potential to produce up to 1.4" of rain in 45-60 minutes. A LOOK AHEAD: Conditions over the District will be dry on Saturday with temperatures continuing to run above seasonal averages. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 800 PM TO 100 AM SAT 0.1" (75%) to 0.3" (50%) to 0.8" (15%) HIGH Arapahoe 800 PM TO 100 AM SAT 0.1" (75%) to 0.3" (50%) to 0.8" (15%) HIGH Boulder 800 PM TO 100 AM SAT 0.1" (60%) to 0.3" (30%) to 0.8" (5%) LOW Broomfield 800 PM TO 100 AM SAT 0.1" (60%) to 0.3" (30%) to 0.8" (5%) LOW Denver 800 PM TO 100 AM SAT 0.1" (75%) to 0.3" (50%) to 0.8" (15%) HIGH Douglas 800 PM TO 100 AM SAT 0.1" (75%) to 0.3" (50%) to 0.8" (15%) HIGH Jefferson 800 PM TO 100 AM SAT 0.1" (60%) to 0.3" (30%) to 0.8" (5%) LOW Foothills above 6500ft       Boulder 800 PM TO 100 AM SAT 0.1" (40%) to 0.3" (20%) to 0.8" (5%) LOW Douglas 800 PM TO 100 AM SAT 0.1" (40%) to 0.3" (20%) to 0.8" (5%) LOW Jefferson 800 PM TO 100 AM SAT 0.1" (40%) to 0.3" (20%) to 0.8" (5%) 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]