Flash Flood Prediction Program

Time: 1050 AM Mon August 12, 2024 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2’S & MESSAGE 1’S ISSUED FOR THE DISTRICT EFFECTIVE FROM 2:00 PM UNTIL 9:00 PM TODAY Message 2’s, Flood Watch, have been issued for central/eastern/southern portions of the District and areas along the foothills effective from 2pm until 9pm this evening. Message 1’s have been issued for the Boulder suburbs, western Broomfield and the Jefferson suburbs effective from 2pm until 9pm this evening. The monsoonal moisture transport setup has strengthened over Colorado and the District today. This has brought the potential for some of the heaviest thunderstorm-driven rainfall of the year this afternoon and into the evening. Dewpoints across the District have dropped only a few degrees this morning, still well into the upper 50s, and will only mix down to the low/mid 50s by the time daytime heating initiates convection over the high country west of the District. As storms make their way east into the foothills and plains by midafternoon, the District will have 1.00"- 1.15" of precipitable water (PWAT) available. Combined with slower storm motions than the past few days, with some stationary storms likely, will lead to an increased chance for localized flooding today. Hail and gusty outflow winds that reach severe thresholds will also be possible with stronger storms, with some potential for severe weather, mainly areas east of I-25. Outflow boundary-driven storm initiation will be possible after the first round of storms today, with potential for lingering thunderstorms around the District remaining through the evening and into the night. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.3-0.8” total in 10- 30 minutes. Strong to severe thunderstorms will have the potential to produce rainfall rates of 0.8- 1.5” total of rain in 10-30 minutes. WORST CASE SCENARIO: A slow-moving strong thunderstorm or a large thunderstorm complex may result in up to 3.0” of rain in 60-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 200 PM TO 900 PM 200 PM TO 900 PM Wheat Ridge 1 200 PM TO 900 PM 200 PM TO 900 PM Arvada 1 200 PM TO 900 PM 200 PM TO 900 PM the City of Aurora 2 200 PM TO 900 PM 200 PM TO 900 PM Arapahoe County 2 200 PM TO 900 PM 200 PM TO 900 PM DIA 2 200 PM TO 900 PM 200 PM TO 900 PM Denver County 2 200 PM TO 900 PM 200 PM TO 900 PM Adams County 2 200 PM TO 900 PM 200 PM TO 900 PM Douglas County 2 200 PM TO 900 PM 200 PM TO 900 PM Broomfield County 2 200 PM TO 900 PM 200 PM TO 900 PM Jefferson County 2 200 PM TO 900 PM 200 PM TO 900 PM Boulder County 2 200 PM TO 900 PM 200 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Arapahoe 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Boulder 200 PM TO 900 PM 0.03" (60%) to 0.8" (30%) to 1.5" (15%) ISSUED Broomfield 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Denver 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Douglas 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Jefferson 200 PM TO 900 PM 0.03" (60%) to 0.8" (30%) to 1.5" (15%) ISSUED Foothills above 6500ft       Boulder 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Douglas 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (30%) ISSUED Jefferson 200 PM TO 900 PM 0.03" (80%) to 0.8" (50%) to 1.5" (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]