Time: 1119 AM Thu July 20, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL CONTINUE VALID UNTIL 11:59 PM Message 1’s will continue to be valid as the threat for heavy rainfall remains. A potent round of storms has moved eastward this morning and out of the District. A few scattered clouds has helped keep temperatures cool this morning. This may help the severity of storms as we head into the afternoon, however, with good upper-level support in place, with elevated surface dew points in the mid to upper 50’s, a good chance for strong to severe storms will be possible this afternoon and evening. Strong to severe storms could produce large hail, up to 1.5”, frequent cloud to ground lightning and heavy rainfall leading to localized flooding. The next round of storms will be between noon and 2pm for western portions of the District with storms moving east between 15-25mph. These storm movements should help limit point rainfall amounts, with the biggest threat being an anchored storm formed along an outflow boundary, or training of thunderstorm cells. Multiple rounds of storms will be possible this afternoon and evening with a slight chance for lingering showers past midnight tonight. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce 0.10-0.50” in 10-30 minutes. A moderate to strong thunderstorm will produce 0.50-1.00” in 10-30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells has the potential to produce up to 2.00” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1159 PM Current TO 1100 PM Jefferson County 1 Current TO 1159 PM Current TO 1100 PM Broomfield County 1 Current TO 1159 PM Current TO 1100 PM Douglas County 1 Current TO 1159 PM Current TO 1100 PM Adams County 1 Current TO 1159 PM Current TO 1100 PM Denver County 1 Current TO 1159 PM Current TO 1100 PM DIA 1 Current TO 1159 PM Current TO 1100 PM Arapahoe County 1 Current TO 1159 PM Current TO 1100 PM the City of Aurora 1 Current TO 1159 PM Current TO 1100 PM Arvada 1 Current TO 1159 PM Current TO 1100 PM Wheat Ridge 1 Current TO 1159 PM Current TO 1100 PM Lakewood 1 Current TO 1159 PM Current TO 1100 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Arapahoe Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Boulder Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Broomfield Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Denver Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Douglas Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Foothills above 6500ft       Boulder Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Douglas Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (30%) ISSUED Jefferson Current TO 1159 PM THU 0.1" (90%) to 0.5" (60%) to 1" (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]