Time: 723 PM Fri July 21, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSGE 1'S ISSUED FOR THE ENTIRE DISTRICT Message 1's have been issued for the entire District and will be valid until 10:30 PM. An upper level disturbance is moving in from the N/NW and will result in a round of thunderstorms for at least northern and central areas of the District this evening. This line of storms may not sustain themselves long enough to impact southern areas of the District and there is a lower risk for heavy rainfall over Arapahoe and Douglas Counties. Storm motions will be from the NW to SE between 20-25mph which will help limit point rainfall amounts. However, training of thunderstorms are possible and may result in an extended period of moderate to heavy rain. Stronger storms may also contain hail and gusty winds. STORM RAINFALL POTENTIAL AND DURATION: Typical showers or a weak thunderstorm will produce a TR-0.3” total in 10-30 minutes. A moderate to strong thunderstorm will have the potential to produce rainfall rates of 0.3-0.8" in 10-30 minutes. WORST CASE SCENARIO: Training of thunderstorm cells may produce up to 1.2" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 1030 PM Current TO 1000 PM Douglas County 1 Current TO 1030 PM Current TO 1000 PM Adams County 1 Current TO 1030 PM Current TO 1000 PM Denver County 1 Current TO 1030 PM Current TO 1000 PM DIA 1 Current TO 1030 PM Current TO 1000 PM Arapahoe County 1 Current TO 1030 PM Current TO 1000 PM the City of Aurora 1 Current TO 1030 PM Current TO 1000 PM Arvada 1 Current TO 1030 PM Current TO 1000 PM Wheat Ridge 1 Current TO 1030 PM Current TO 1000 PM Broomfield County 1 Current TO 1030 PM Current TO 1000 PM Jefferson County 1 Current TO 1030 PM Current TO 1000 PM Boulder County 1 Current TO 1030 PM Current TO 1000 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1030 PM FRI 0.1" (90%) to 0.4" (50%) to 0.8" (25%) ISSUED Arapahoe Current TO 1030 PM FRI 0.1" (75%) to 0.4" (30%) to 0.8" (10%) ISSUED Boulder Current TO 1030 PM FRI 0.1" (100%) to 0.4" (60%) to 0.8" (30%) ISSUED Broomfield Current TO 1030 PM FRI 0.1" (90%) to 0.4" (50%) to 0.8" (25%) ISSUED Denver Current TO 1030 PM FRI 0.1" (85%) to 0.4" (45%) to 0.8" (20%) ISSUED Douglas Current TO 1030 PM FRI 0.1" (60%) to 0.4" (30%) to 0.8" (10%) ISSUED Jefferson Current TO 1030 PM FRI 0.1" (85%) to 0.4" (45%) to 0.8" (20%) ISSUED Foothills above 6500ft       Boulder Current TO 1030 PM FRI 0.1" (100%) to 0.4" (60%) to 0.8" (30%) ISSUED Douglas Current TO 1030 PM FRI 0.1" (60%) to 0.4" (30%) to 0.8" (10%) ISSUED Jefferson Current TO 1030 PM FRI 0.1" (85%) to 0.4" (45%) to 0.8" (20%) 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]