Flash Flood Prediction Program

Time: 1212 PM Tue April 27, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR PORTIONS OF THE DISTRICT - Message 1's have been issued for Adams, Arapahoe/Aurora, Denver/DIA, and Douglas Counties and are valid until 8pm this evening. - Thunderstorms have developed E of I-25 over the District as an upper level low pressure system emerges onto the plains. Thunderstorm activity will continue possible through the afternoon becoming less likely after 5 or 6pm as temperatures cool and precipitation becomes more stratiform in nature versus convective currently. - The stronger thunderstorm activity is expected to remain confined to areas generally along and E of I-25 as there is better surface convergence with weaker storms westward towards the foothills. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will have the potential to produce 0.1-0.5" of rain in 10-30 minutes. Weak/moderate and briefly strong thunderstorms will have the potential to produce 0.3-0.9" of rain in 10-30 minutes. Strong thunderstorms are expected to produce more hail than rainfall. Steady moderate to heavy rain may produce 0.4-1.2" in 45-75 minutes. WORST CASE SCENARIO: Training of thunderstorm cells may produce up to 1.4" in 45-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Douglas County 1 Current TO 800 PM Current TO 600 PM Adams County 1 Current TO 800 PM Current TO 600 PM Denver County 1 Current TO 800 PM Current TO 600 PM DIA 1 Current TO 800 PM Current TO 600 PM Arapahoe County 1 Current TO 800 PM Current TO 600 PM the City of Aurora 1 Current TO 800 PM Current TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 60-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 800 PM TUE 0.1" (100%) to 0.5" (80%) to 1.2" (25%) ISSUED Arapahoe Current TO 800 PM TUE 0.1" (100%) to 0.5" (80%) to 1.2" (25%) ISSUED Boulder Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.2" (10%) LOW Broomfield Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.2" (10%) LOW Denver Current TO 800 PM TUE 0.1" (100%) to 0.5" (80%) to 1.2" (25%) ISSUED Douglas Current TO 800 PM TUE 0.1" (100%) to 0.5" (80%) to 1.2" (25%) ISSUED Jefferson Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.2" (10%) LOW Foothills above 6500ft       Boulder Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.0" (10%) LOW Douglas Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.0" (10%) LOW Jefferson Current TO 800 PM TUE 0.1" (100%) to 0.5" (60%) to 1.0" (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]