Flash Flood Prediction Program

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

Multiple ingredients are in place today for thunderstorms to become strong to severe in and around the District. The first storms are beginning to develop over the foothills and these initial storms may dissipate as the air mass is still a little cool to support surface based convection over the plains. As the afternoon progresses storms are expected to blossom and become scattered producing brief heavy rainfall, hail, gusty winds and possibly a very isolated tornado.

Typical storms will move from W to E or NNW to ESE at 20-25mph with stronger storms possibly splitting and moving more slowly/erratically. Fast storm motions will help to reduce point rainfall amounts, but a large thunderstorm or training of thunderstorm cells could produce 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 0.1-0.5” of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.5” in 10-30 minutes.

WORST CASE SCENARIO: A slower moving large thunderstorm or training of thunderstorm cells may result in up to 2.5” of rain in 45-75 minutes.

County	Message	Valid Times	Prime Time
Boulder County	1	Current TO 1000 PM	130 PM TO 900 PM
Jefferson County	1	Current TO 1000 PM	130 PM TO 900 PM
Broomfield County	1	Current TO 1000 PM	130 PM TO 900 PM
Douglas County	1	Current TO 1000 PM	130 PM TO 900 PM
Adams County	1	Current TO 1000 PM	130 PM TO 900 PM
Denver County	1	Current TO 1000 PM	130 PM TO 900 PM
DIA	1	Current TO 1000 PM	130 PM TO 900 PM
Arapahoe County	1	Current TO 1000 PM	130 PM TO 900 PM
the City of Aurora	1	Current TO 1000 PM	130 PM TO 900 PM
Arvada	1	Current TO 1000 PM	130 PM TO 900 PM
Wheat Ridge	1	Current TO 1000 PM	130 PM TO 900 PM
Lakewood	1	Current TO 1000 PM	130 PM TO 900 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	100 PM TO 1000 PM	0.1" (95%) to 0.5" (60%) to 1.5" (30%)	ISSUED
Arapahoe	100 PM TO 1000 PM	0.1" (95%) to 0.5" (60%) to 1.5" (30%)	ISSUED
Boulder	100 PM TO 1000 PM	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Broomfield	100 PM TO 1000 PM	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Denver	100 PM TO 1000 PM	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Douglas	Current TO 1000 PM THU	0.1" (95%) to 0.5" (60%) to 1.5" (30%)	ISSUED
Jefferson	Current TO 1000 PM THU	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 1000 PM THU	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Douglas	Current TO 1000 PM THU	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED
Jefferson	Current TO 1000 PM THU	0.1" (95%) to 0.5" (60%) to 1.5" (25%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.