Time: 927 AM Thu July 1, 2021 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2'S ISSUED AND VALID FROM 11AM TO MIDNIGHT - Message 2's will become valid at 11:00am as thunderstorms that develop today will be very capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. Multiple rounds of strong thunderstorms are expected through the afternoon and evening. - Thunderstorms will first develop over the foothills and Palmer Divide by 11am to noon. Thunderstorms will begin to move onto the plains between 1-2pm. Training of thunderstorm cells or large slower moving thunderstorms will be the main culprits for extended periods of heavy rainfall. Upper level steering winds are light from W/WSW to E/ENE at 10-15mph. Roadways/smaller creeks and streams will be most prone to excessive runoff/flooding today. - Prime time for strong thunderstorms over the plains is from 1-9pm. After 9 or 10pm the thunderstorm activity is expected to have pushed east of the District with lingering light rain showers possible into the evening. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" of rain in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce heavy rainfall rates of 0.6-1.8" in 10-30 minutes WORST CASE SCENARIO: Training of thunderstorm cells or a large slow moving strong thunderstorm may result in very heavy rainfall of up to 4.0" in 60-90 minutes. Should rain continue for longer than 90 minutes in duration higher amounts are possible. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Jefferson County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Broomfield County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Douglas County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Adams County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Denver County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM DIA 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Arapahoe County 2 1100 AM TO 1159 PM 1100 AM TO 900 PM the City of Aurora 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Arvada 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Wheat Ridge 2 1100 AM TO 1159 PM 1100 AM TO 900 PM Lakewood 2 1100 AM TO 1159 PM 1100 AM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Arapahoe 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Boulder 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Broomfield 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Denver 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Douglas 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Jefferson 1200 PM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Foothills above 6500ft       Boulder 1100 AM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Douglas 1100 AM TO 1159 PM 0.3" (95%) to 0.9" (60%) to 1.8" (30%) ISSUED Jefferson 1100 AM TO 1159 PM 0.3" (95%) to 0.9" (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]