Flash Flood Prediction Program

Message 1’s have been issued for the entire District and will be valid until 10:00 PM this evening.

Thunderstorms to the south of the District have developed over the crest of the Palmer Divide and have produced a rain cooled outflow boundary that is moving to the N and will enter the District over the next hour. This boundary will likely initiate new thunderstorm development as it progresses northward this afternoon with slow moving, strong storms possible into the evening. Best chances for thunderstorms will be through 9 or 10:00 PM with additional lighter rain showers continuing into the early overnight period.

Upper level steering winds are very light from S/SSE to N/NNW at 10mph or less. Strong thunderstorms may move very little or remain stationary. The slow motion of the storms may result in extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. The ground is also saturated over many areas within the District and it may not take as much rain as normal to produce runoff.

STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce rainfall rates of 0.1-0.5” in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.3” in 10-30 minutes.

WORST CASE SCENARIO: A slow moving or nearly stationary strong thunderstorm may result in up to 2.0” of rain in 45-60 minutes.

County	Message	Valid Times	Prime Time
Boulder County	1	Current TO 1000 PM	300 PM TO 900 PM
Jefferson County	1	Current TO 1000 PM	300 PM TO 900 PM
Broomfield County	1	Current TO 1000 PM	300 PM TO 900 PM
Douglas County	1	Current TO 1000 PM	300 PM TO 900 PM
Adams County	1	Current TO 1000 PM	300 PM TO 900 PM
Denver County	1	Current TO 1000 PM	300 PM TO 900 PM
DIA	1	Current TO 1000 PM	300 PM TO 900 PM
Arapahoe County	1	Current TO 1000 PM	300 PM TO 900 PM
the City of Aurora	1	Current TO 1000 PM	300 PM TO 900 PM
Arvada	1	Current TO 1000 PM	300 PM TO 900 PM
Wheat Ridge	1	Current TO 1000 PM	300 PM TO 900 PM
Lakewood	1	Current TO 1000 PM	300 PM TO 900 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	300 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Broomfield	300 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Arapahoe	230 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Boulder	230 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Denver	230 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Jefferson	230 PM TO 1000 PM	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Douglas	Current TO 1000 PM WED	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Foothills above 6500ft
Boulder	Current TO 1000 PM WED	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Douglas	Current TO 1000 PM WED	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH
Jefferson	Current TO 1000 PM WED	0.1" (80%) to 0.5" (50%) to 1.3" (25%)	HIGH

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.