Time: 408 PM Tue April 27, 2021 Forecaster: Brad Simmons

Internal Message Status
Flash Flood Prediction Program

MESSAGE 1'S CONTINUE VALID FOR PORTIONS OF THE DISTRICT
-Message 1's issued earlier for Adams, Arapahoe/Aurora, Denver/DIA, and Douglas Counties will remain valid until 8pm this evening.
-The strongest thunderstorm activity has exited the District and remained well E of I-25 with weaker rain showers and isolated thunderstorms currently in/around the District. A stronger storm cannot be ruled out over the next few hours before the convective nature of the showers becomes more stratiform and a widespread rain develops this evening.
-Rain will be changing over to snow in the foothills above 8,000' by sunset and the snow line will slowly lower to around 6,000' by tomorrow morning, possibly as low as 5,000' briefly. As temperatures cool this evening and a more "upslope" flow develops the rain will be widespread but light to moderate resulting in minor runoff but no flash flood threat exists.
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. Briefly strong thunderstorms will have the potential to produce 0.3-0.9" of rain in 10-30 minutes. Steady moderate to heavy non-thunderstorm rain may produce 0.4-1.2" in 45-75 minutes early this evening.

WORST CASE SCENARIO: Training of thunderstorm cells may produce up to 1.4" in 45-75 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 0.4" (60%) to 1.0" (15%) ISSUED
Arapahoe Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) ISSUED
Boulder Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) LOW
Broomfield Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) LOW
Denver Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) ISSUED
Douglas Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) ISSUED
Jefferson Current TO 800 PM TUE
0.1" (100%) to 0.4" (60%) to 1.0" (15%) LOW
Foothills above 6500ft      
Boulder Current TO 800 PM TUE
0.1" (100%) to 0.4" (50%) to 1.0" (5%) NONE
Douglas Current TO 800 PM TUE
0.1" (100%) to 0.4" (50%) to 1.0" (5%) NONE
Jefferson Current TO 800 PM TUE
0.1" (100%) to 0.4" (50%) to 1.0" (5%) NONE
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.