Time: 126 PM Sun July 21, 2024 Forecaster: Laura Smith ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S HAVE BEEN ISSUED EFFECTIVE UNTIL 10:00 PM Storms have started to impact areas along the higher terrain foothills where a few moderate showers have already produced rainfall rates between 0.30”-0.80” in 20-30 minutes. Cooler temperatures this morning have helped limit storm development, however as we move into the afternoon the threat of moderate to heavy rainfall will be possible across the entire District. The best chance for storm activity today will begin in the next hour with a chance for storms into the evening hours. Storm motions will generally be NW to SE with some erratic storm motions likely from outflow boundaries into the evening. Some storms will have the potential to anchor in place supporting clustering thunderstorms with a threat for longer lasting moderate to heavy rainfall. A quick 0.50”-0.80” in 10-20 minutes is expected, along with the possibility for over 1.0” of rain per hour if a stronger storm stalls over the District. Storms today may also contain hail up to 1.0”, gusty winds up to 50mph and frequent cloud-to-ground lightning. A slight chance of showers lingers through midnight, although the threat of heavy rainfall will likely subside by 10pm this evening. A few off and on showers may persist overnight with skies gradually clearing by daybreak tomorrow. Overnight temperatures will drop into the low 60s for the plains with mid to upper 50s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.30”-0.60” in 10-30 minutes. A slow-moving thunderstorm or a large thunderstorm complex may result in up to 1.25” of rain in 45-60 minutes. WORST CASE SCENARIO: A strong/stationary thunderstorm or a training of heavy showers may produce 2.00" in 30 minutes or less, resulting in excessive runoff and possible flash flooding. COUNTY MESSAGE VALID TIMES PRIME TIME Wheat Ridge 1 Current TO 1000 PM 200 PM TO 1000 PM Arvada 1 Current TO 1000 PM 200 PM TO 1000 PM the City of Aurora 1 Current TO 1000 PM 200 PM TO 1000 PM DIA 1 Current TO 1000 PM 200 PM TO 1000 PM Arapahoe County 1 Current TO 1000 PM 200 PM TO 1000 PM Adams County 1 Current TO 1000 PM 200 PM TO 1000 PM Denver County 1 Current TO 1000 PM 200 PM TO 1000 PM Broomfield County 1 Current TO 1000 PM 200 PM TO 1000 PM Douglas County 1 Current TO 1000 PM 200 PM TO 1000 PM Jefferson County 1 Current TO 1000 PM 200 PM TO 1000 PM Boulder County 1 Current TO 1000 PM 200 PM TO 1000 PM Lakewood 1 Current TO 1000 PM 200 PM TO 1000 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Arapahoe Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Boulder Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Broomfield Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Denver Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Douglas Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Jefferson Current TO 1000 PM SUN 0.3" (75%) to 0.6" (50%) to 1.2" (25%) HIGH Foothills above 6500ft       Boulder Current TO 1000 PM SUN 0.3" (80%) to 0.6" (60%) to 1.2" (40%) HIGH Douglas Current TO 1000 PM SUN 0.3" (80%) to 0.6" (60%) to 1.2" (40%) HIGH Jefferson Current TO 1000 PM SUN 0.3" (80%) to 0.6" (60%) to 1.2" (40%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]