Flash Flood Prediction Program

Time: 332 PM Sat May 27, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGES ISSUED FOR PORTIONS OF THE DISTRICT Message 1’s have been issued for Adams, Arapahoe, Boulder, Broomfield and Denver Counties and will be valid until 8:00pm this evening. Moisture has scoured out over S and SW areas of the District over Douglas and Jefferson Counties with higher moisture values over northern areas of the District. Northern areas of the District will have better chances for a stronger storm this afternoon and early evening. 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. Best chances for thunderstorms will be over the next 3-4 hours then chances decrease after 7:00pm. 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 an outflow boundary from northern storms push back to the south and replenish surface moisture additional Message 1’s may be issued for Jefferson and Douglas Counties. 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 Broomfield County 1 Current TO 800 PM Current TO 700 PM Boulder County 1 Current TO 800 PM Current TO 700 PM DIA 1 Current TO 800 PM Current TO 700 PM Arapahoe County 1 Current TO 800 PM Current TO 700 PM the City of Aurora 1 Current TO 800 PM Current TO 700 PM Arvada 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 Denver County 1 Current TO 800 PM Current TO 700 PM Adams County 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" (70%) to 0.3" (30%) to 0.9" (10%) 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" (50%) to 0.3" (25%) to 0.9" (5%) LOW Jefferson Current TO 800 PM SAT 0.1" (50%) to 0.3" (25%) to 0.9" (5%) LOW 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%) LOW Jefferson Current TO 800 PM SAT 0.1" (60%) to 0.3" (30%) to 0.9" (10%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]