Flash Flood Prediction Program

-	Message 1's have been issued for the southern areas of the District (Arapahoe, Douglas and Jefferson Counties) and will be valid until 9:00 pm. Additional Message 1's may be issued for the remainder of the District if the threat for heavy rain increases northward.
-	Thunderstorms are starting to develop over the higher terrain to the W of the District and will be moving onto the foothills and Palmer Divide over the next couple hours. As these storms progress NE'ward they are expected to encounter a cooler and more stable air mass over the plains likely weakening the storms as they move onto the lower elevations.
-	Strongest storms at this time look to favor the foothills and Palmer Divide favoring Jefferson and Douglas Counties but storms may be far enough N to impact Arapahoe County as well. Thunderstorms will be very capable of producing heavy rainfall that could lead to excessive runoff and possibly flash flooding. Storms will move from SW to NE at around 10-15mph which will allow for larger storms to potentially produce an extended period of heavy rainfall.

STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers and weak thunderstorms will produce a trace to 0.4" of rain in 10-30 minutes. Moderate thunderstorms will have the potential to produce 0.4-1.2" in 10-30 minutes. Supplemental QPF is available at https://qpf.udfcd.org

WORST CASE SCENARIO: A strong thunderstorm, if able to develop will have the potential to produce 0.5-1.5" of heavy rain in 10-30 minutes and up to 2.2" in 45-60 minutes.

County	Message	Valid Times	Prime Time
Wheat Ridge	1	1230 PM TO 900 PM	130 PM TO 800 PM
Lakewood	1	1230 PM TO 900 PM	130 PM TO 800 PM
Arvada	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
Douglas County	1	1230 PM TO 900 PM	130 PM TO 800 PM
Arapahoe 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

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	130 PM TO 900 PM	0.1" (60%) to 0.4" (40%) to 1.2" (10%)	LOW
Arapahoe	130 PM TO 900 PM	0.1" (80%) to 0.4" (60%) to 1.2" (20%)	ISSUED
Boulder	130 PM TO 900 PM	0.1" (60%) to 0.4" (40%) to 1.2" (10%)	LOW
Broomfield	130 PM TO 900 PM	0.1" (60%) to 0.4" (40%) to 1.2" (10%)	LOW
Denver	130 PM TO 900 PM	0.1" (70%) to 0.4" (50%) to 1.2" (15%)	MOD
Douglas	130 PM TO 900 PM	0.1" (95%) to 0.4" (65%) to 1.2" (25%)	ISSUED
Jefferson	130 PM TO 900 PM	0.1" (80%) to 0.4" (60%) to 1.2" (20%)	ISSUED
Foothills above 6500ft
Boulder	100 PM TO 900 PM	0.1" (80%) to 0.4" (40%) to 1.2" (10%)	LOW
Douglas	100 PM TO 900 PM	0.1" (100%) to 0.4" (70%) to 1.2" (30%)	ISSUED
Jefferson	100 PM TO 900 PM	0.1" (95%) to 0.4" (65%) to 1.2" (20%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.