Flash Flood Prediction Program

Message 1’s have been issued for the entire District and will be valid until 9:00pm this evening.

Daytime heating is already starting to generate thunderstorm activity over the foothills and storms will begin to move over the plains over the next few hours. Surface moisture is abundant with dew points currently in the lower 50’s which will be fuel for thunderstorms this afternoon. Stronger thunderstorms will be capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. Strong thunderstorms will also contain large hail, frequent cloud-to-ground lightning and gusty winds.

1-2 rounds of thunderstorms are expected through the course of the afternoon. Typical thunderstorms will move from SW to NE at around 15mph but stronger storms may move more slowly or erratically. After 8 or 9pm the thunderstorm activity is expected to have pushed to the east of the District with possibly a few lingering lighter rain showers persisting into the late evening.

STORM RAINFALL POTENTIAL AND DURATION: Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.4-1.0” in 10-30 minutes.

WORST CASE SCENARIO: A slower moving strong thunderstorm or a large thunderstorm complex may result in up to 1.8” of rain in 45-60 minutes.

County	Message	Valid Times	Prime Time
Lakewood	1	1230 PM TO 900 PM	130 PM TO 800 PM
Wheat Ridge	1	1230 PM TO 900 PM	130 PM TO 800 PM
the City of Aurora	1	1230 PM TO 900 PM	130 PM TO 800 PM
DIA	1	1230 PM TO 900 PM	130 PM TO 800 PM
Arapahoe County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Denver County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Adams County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Douglas County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Broomfield County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Jefferson County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Boulder County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Arvada	1	1230 PM TO 900 PM	130 PM TO 800 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	100 PM TO 900 PM	0.1" (90%) to 0.5" (60%) to 1" (30%)	ISSUED
Arapahoe	100 PM TO 900 PM	0.1" (90%) to 0.5" (60%) to 1" (30%)	ISSUED
Boulder	100 PM TO 900 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Broomfield	100 PM TO 900 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Denver	100 PM TO 900 PM	0.1" (90%) to 0.5" (55%) to 1" (20%)	ISSUED
Douglas	100 PM TO 900 PM	0.1" (90%) to 0.5" (60%) to 1" (30%)	ISSUED
Jefferson	100 PM TO 900 PM	0.1" (90%) to 0.5" (50%) to 1" (20%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 900 PM FRI	0.1" (95%) to 0.5" (65%) to 1" (30%)	ISSUED
Douglas	Current TO 900 PM FRI	0.1" (95%) to 0.5" (65%) to 1" (30%)	ISSUED
Jefferson	Current TO 900 PM FRI	0.1" (95%) to 0.5" (65%) to 1" (30%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.