Flash Flood Prediction Program

-	Message 1's have been issued and will be valid for the entire District until 9:30 PM.
-	Thunderstorm development outside the District to the N and S/SE has produced multiple outflow boundaries which will move through the District and may act as triggers for new thunderstorms over the coming hours. Slow moving or stationary thunderstorm that develop along these surface wind convergence boundaries may move very slowly or remain stationary producing the potential for heavy rainfall. Strong thunderstorms may also contain gusty winds, hail and frequent cloud-to-ground lightning.
-	Thunderstorms are currently erupting over NW Jefferson County and portions of Arapahoe County with new storms expected to fill in over other areas of the District shortly. Prime time for thunderstorm activity is through 8:30 PM. Upper level winds will carry individual storms from NW to SE at around 15mph. Slow moving or briefly anchored storms will produce the greatest threat for extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding.

STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.4-1.2" in 10-30 minutes.

WORST CASE SCENARIO: A 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 930 PM	530 PM TO 830 PM
Jefferson County	1	Current TO 930 PM	500 PM TO 830 PM
Broomfield County	1	Current TO 930 PM	530 PM TO 830 PM
Douglas County	1	Current TO 930 PM	530 PM TO 830 PM
Adams County	1	Current TO 930 PM	530 PM TO 830 PM
Denver County	1	Current TO 930 PM	530 PM TO 830 PM
DIA	1	Current TO 930 PM	530 PM TO 830 PM
Arapahoe County	1	Current TO 930 PM	500 PM TO 830 PM
the City of Aurora	1	Current TO 930 PM	530 PM TO 830 PM
Arvada	1	Current TO 930 PM	530 PM TO 830 PM
Wheat Ridge	1	Current TO 930 PM	530 PM TO 830 PM
Lakewood	1	Current TO 930 PM	530 PM TO 830 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	Current TO 900 PM FRI	0.1" (75%) to 0.4" (50%) to 1.0" (15%)	ISSUED
Arapahoe	Current TO 900 PM FRI	0.1" (90%) to 0.4" (60%) to 1.0" (30%)	ISSUED
Boulder	Current TO 900 PM FRI	0.1" (80%) to 0.4" (50%) to 1.0" (20%)	ISSUED
Broomfield	Current TO 900 PM FRI	0.1" (75%) to 0.4" (50%) to 1.0" (15%)	ISSUED
Denver	Current TO 900 PM FRI	0.1" (75%) to 0.4" (50%) to 1.0" (15%)	ISSUED
Douglas	Current TO 900 PM FRI	0.1" (75%) to 0.4" (50%) to 1.0" (15%)	ISSUED
Jefferson	Current TO 900 PM FRI	0.1" (90%) to 0.4" (60%) to 1.0" (30%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 900 PM FRI	0.1" (85%) to 0.4" (50%) to 1.0" (20%)	ISSUED
Douglas	Current TO 900 PM FRI	0.1" (85%) to 0.4" (50%) to 1.0" (20%)	ISSUED
Jefferson	Current TO 900 PM FRI	0.1" (85%) to 0.4" (50%) to 1.0" (20%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.