Flash Flood Prediction Program

Message 1’s have been issued for the entire District and will be valid until 8:00pm this evening.

Abundant surface moisture with dew points in the low to mid 50’s and a passing upper level disturbance will result in thunderstorms developing initiating over the next 1-2 hours over the higher terrain to the W and S of the District. One round of moderate to strong thunderstorms is expected through the course of the afternoon with a weaker round possible in the evening. Typical thunderstorms will be relatively slow moving from SW to NE at around 15mph, but stronger thunderstorm cells may move slower and against the grain from NW to SE.

Strong thunderstorms will be capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. After 8:00pm the thunderstorm activity is expected to have pushed east of the District with conditions drying out into the later evening.

STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce rainfall rates of 0.2-0.5” of rain 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 strong thunderstorm or training of thunderstorm cells may result in up to 2.0” of rain in 45-60 minutes.

County	Message	Valid Times	Prime Time
the City of Aurora	1	1200 PM TO 800 PM	100 PM TO 700 PM
Arapahoe County	1	1200 PM TO 800 PM	100 PM TO 700 PM
DIA	1	1200 PM TO 800 PM	100 PM TO 700 PM
Denver County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Adams County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Douglas County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Broomfield County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Jefferson County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Boulder County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Lakewood	1	1200 PM TO 800 PM	100 PM TO 700 PM
Arvada	1	1200 PM TO 800 PM	100 PM TO 700 PM
Wheat Ridge	1	1200 PM TO 800 PM	100 PM TO 700 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (25%)	ISSUED
Arapahoe	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (25%)	ISSUED
Boulder	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Broomfield	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Denver	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (25%)	ISSUED
Douglas	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (25%)	ISSUED
Jefferson	100 PM TO 800 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 800 PM WED	0.1" (95%) to 0.5" (50%) to 1" (20%)	ISSUED
Douglas	Current TO 800 PM WED	0.1" (95%) to 0.5" (50%) to 1" (20%)	ISSUED
Jefferson	Current TO 800 PM WED	0.1" (95%) to 0.5" (50%) to 1" (20%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.