Time: 215 PM Fri July 23, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT - Message 1's have been issued for the entire District and will remain valid until 10pm this evening. - A gust front is on the approach from storms that developed over Weld County earlier today and will likely be a trigger for thunderstorms over the coming hours as it moves through the District from N to S. Slow to nearly stationary storm motions will allow for extended periods of heavy rain under stronger storms that are able to develop this afternoon/evening which may lead to excessive runoff and possibly flash flooding. - QPF estimates have increased from this morning as moisture levels are expected to rise into the later afternoon/evening over the District. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.2-0.6" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 3.2" in 60-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1000 PM 300 PM TO 900 PM Jefferson County 1 Current TO 1000 PM 330 PM TO 900 PM Broomfield County 1 Current TO 1000 PM 400 PM TO 900 PM Douglas County 1 Current TO 1000 PM 400 PM TO 900 PM Adams County 1 Current TO 1000 PM 400 PM TO 900 PM Denver County 1 Current TO 1000 PM 400 PM TO 900 PM DIA 1 Current TO 1000 PM 400 PM TO 900 PM Arapahoe County 1 Current TO 1000 PM 400 PM TO 900 PM the City of Aurora 1 Current TO 1000 PM 400 PM TO 900 PM Arvada 1 Current TO 1000 PM 400 PM TO 900 PM Wheat Ridge 1 Current TO 1000 PM 400 PM TO 900 PM Lakewood 1 Current TO 1000 PM 400 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1000 PM 0.2" (75%) to 0.6" (40%) to 1.8" (20%) ISSUED Arapahoe 300 PM TO 1000 PM 0.2" (75%) to 0.6" (40%) to 1.8" (20%) ISSUED Boulder 300 PM TO 1000 PM 0.2" (80%) to 0.6" (50%) to 1.8" (20%) ISSUED Broomfield 300 PM TO 1000 PM 0.2" (80%) to 0.6" (50%) to 1.8" (20%) ISSUED Denver 300 PM TO 1000 PM 0.2" (75%) to 0.6" (40%) to 1.8" (20%) ISSUED Douglas 300 PM TO 1000 PM 0.2" (80%) to 0.6" (50%) to 1.8" (20%) ISSUED Jefferson 300 PM TO 1000 PM 0.2" (80%) to 0.6" (50%) to 1.8" (20%) ISSUED Foothills above 6500ft       Boulder 300 PM TO 1000 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) ISSUED Douglas 300 PM TO 1000 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) ISSUED Jefferson 300 PM TO 1000 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]