Flash Flood Prediction Program

Time: 442 PM Sat May 27, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S NOW ISSUED FOR THE ENTIRE DISTRICT Message 1’s now includes all areas of the District and will be valid until 8:00pm this evening. Outflow boundaries from previous storms are pushing moisture back to the W and is increasing the surface moisture which will help fuel thunderstorms. Northern and eastern areas of the District still have better chances for a stronger storm this afternoon and early evening as the moisture is more abundant in this zone. Storms over the foothills are expected to be weaker than plains storms. Much like the past few days the stronger storms will be capable of producing hail as well as brief moderate to heavy rainfall that may lead to excessive runoff roadways. Most storms will be weak to moderate with just a slight chance for a stronger thunderstorm. Best chances for thunderstorms will be over the next few hours then chances decrease after 7:30pm. Typical storms will move from SW to NE at around 20mph and the relatively fast storm motions will help to reduce point rainfall amounts. A large thunderstorm or a slower moving thunderstorm will be the culprits for extended periods of heavy rain should they develop. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.1-0.3" of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.3-0.9” in 10-30 minutes. WORST CASE SCENARIO: A slow moving strong thunderstorm or large thunderstorm cell may result in up to 1.5” of rain in 45-60 minutes COUNTY MESSAGE VALID TIMES PRIME TIME Arvada 1 Current TO 800 PM Current TO 700 PM the City of Aurora 1 Current TO 800 PM Current TO 700 PM Arapahoe County 1 Current TO 800 PM Current TO 700 PM DIA 1 Current TO 800 PM Current TO 700 PM Denver County 1 Current TO 800 PM Current TO 700 PM Adams County 1 Current TO 800 PM Current TO 700 PM Douglas County 1 Current TO 800 PM Current TO 700 PM Broomfield County 1 Current TO 800 PM Current TO 700 PM Jefferson County 1 Current TO 800 PM Current TO 700 PM Boulder County 1 Current TO 800 PM Current TO 700 PM Wheat Ridge 1 Current TO 800 PM Current TO 700 PM Lakewood 1 Current TO 800 PM Current TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 800 PM SAT 0.1" (80%) to 0.3" (40%) to 0.9" (20%) ISSUED Arapahoe Current TO 800 PM SAT 0.1" (75%) to 0.3" (35%) to 0.9" (15%) ISSUED Boulder Current TO 800 PM SAT 0.1" (85%) to 0.3" (50%) to 0.9" (25%) ISSUED Broomfield Current TO 800 PM SAT 0.1" (85%) to 0.3" (50%) to 0.9" (25%) ISSUED Denver Current TO 800 PM SAT 0.1" (80%) to 0.3" (40%) to 0.9" (20%) ISSUED Douglas Current TO 800 PM SAT 0.1" (75%) to 0.3" (30%) to 0.9" (15%) ISSUED Jefferson Current TO 800 PM SAT 0.1" (75%) to 0.3" (30%) to 0.9" (15%) ISSUED Foothills above 6500ft       Boulder Current TO 800 PM SAT 0.1" (60%) to 0.3" (30%) to 0.9" (10%) ISSUED Douglas Current TO 800 PM SAT 0.1" (60%) to 0.3" (30%) to 0.9" (10%) ISSUED Jefferson Current TO 800 PM SAT 0.1" (60%) to 0.3" (30%) to 0.9" (10%) 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]