Flash Flood Prediction Program

Time: 1105 PM Thu July 20, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL BE ALLOWED TO EXPIRE AT MIDNIGHT Message 1’s will be allowed to expire at midnight as the threat for heavy rainfall has ended. A few additional widely scattered rain showers and possibly a very isolated weak thunderstorm will remain possible into the early morning hours on Friday. Best chances for additional precipitation will be through 3 or 4am then completely dry conditions are expected to develop in and around the District. Areas of patchy fog may develop overnight over the plains but should burn off quickly early tomorrow morning. A significant decrease in storm activity will occur on Friday as the upper level disturbance that produced the multiple waves of storms today will push eastward. Temperatures will continue to be below seasonal averages with highs in the 80’s over the plains with 70's in the Front Range foothills. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and possibly a very isolated weak thunderstorm will produce a trace to 0.2” of rain. WORST CASE SCENARIO: Although unlikely, if a moderate thunderstorm is able to develop it will be capable of producing rainfall rates of 0.1-0.4” in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Jefferson County 1 Current TO 1159 PM Current TO 1130 PM Boulder County 1 Current TO 1159 PM Current TO 1130 PM the City of Aurora 1 Current TO 1159 PM Current TO 1130 PM Arapahoe County 1 Current TO 1159 PM Current TO 1130 PM DIA 1 Current TO 1159 PM Current TO 1130 PM Denver County 1 Current TO 1159 PM Current TO 1130 PM Adams County 1 Current TO 1159 PM Current TO 1130 PM Douglas County 1 Current TO 1159 PM Current TO 1130 PM Broomfield County 1 Current TO 1159 PM Current TO 1130 PM Lakewood 1 Current TO 1159 PM Current TO 1130 PM Arvada 1 Current TO 1159 PM Current TO 1130 PM Wheat Ridge 1 Current TO 1159 PM Current TO 1130 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Arapahoe Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Boulder Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Broomfield Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Denver Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Douglas Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Jefferson Current TO 400 AM FRI Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Foothills above 6500ft       Boulder Current TO 400 AM FRI Trace (70%) to 0.1" (40%) to 0.2" (10%) NONE Douglas Current TO 400 AM FRI Trace (70%) to 0.1" (40%) to 0.2" (10%) NONE Jefferson Current TO 400 AM FRI Trace (70%) to 0.1" (40%) to 0.2" (10%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]