Flash Flood Prediction Program

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

Thunderstorms have developed over the foothills but are very slow moving and these initial storms will likely not be the storms that impact the I-25 corridor later this afternoon. Rain cooled air from these initial storms in the form of a gust front/outflow boundary pushing eastward and acting as a “trigger” will be the likely culprit for new storm development over the plains.

Storms will be slow moving from W to E or may remain nearly stationary and have the potential to produce heavy rainfall as surface moisture remains abundant with dew points in the 50’s. Best chances for thunderstorms over the plains will be from 3:30-8:30 PM. Due to all of the rainfall yesterday the ground is saturated in some areas and it may not take as much rain today to produce excessive runoff and possibly flash flooding.

STORM RAINFALL POTENTIAL AND DURATION: 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 slow moving strong thunderstorm or nearly stationary thunderstorm may result in up to 2.0” of rain in 60 minutes or less.

County	Message	Valid Times	Prime Time
the City of Aurora	1	225 PM TO 900 PM	330 PM TO 830 PM
Arapahoe County	1	225 PM TO 900 PM	330 PM TO 830 PM
DIA	1	225 PM TO 900 PM	330 PM TO 830 PM
Denver County	1	225 PM TO 900 PM	330 PM TO 830 PM
Adams County	1	225 PM TO 900 PM	330 PM TO 830 PM
Douglas County	1	225 PM TO 900 PM	330 PM TO 830 PM
Broomfield County	1	225 PM TO 900 PM	330 PM TO 830 PM
Jefferson County	1	225 PM TO 900 PM	330 PM TO 830 PM
Boulder County	1	225 PM TO 900 PM	330 PM TO 830 PM
Arvada	1	225 PM TO 900 PM	330 PM TO 830 PM
Wheat Ridge	1	225 PM TO 900 PM	330 PM TO 830 PM
Lakewood	1	225 PM TO 900 PM	330 PM TO 830 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Arapahoe	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Boulder	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Broomfield	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Denver	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Douglas	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Jefferson	300 PM TO 900 PM	0.1" (80%) to 0.4" (50%) to 1.2" (25%)	ISSUED
Foothills above 6500ft
Boulder	300 PM TO 900 PM	0.1" (90%) to 0.4" (60%) to 1.2" (25%)	ISSUED
Douglas	300 PM TO 900 PM	0.1" (90%) to 0.4" (60%) to 1.2" (25%)	ISSUED
Jefferson	300 PM TO 900 PM	0.1" (90%) to 0.4" (60%) to 1.2" (25%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.