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.