Flash Flood Prediction Program

-	Message 1's have been issued for all areas of the District except Douglas County at this time and will be valid until 6:00pm this evening. Douglas County may be added over the next hour.
-	Thunderstorm activity is beginning to initiate over the higher terrain associated with a potent upper level trough of low pressure and will begin to spread out onto the plains shortly. Fast storm motions from SSW to NNE at 30-40mph will limit point rainfall amounts from a singe storm, likely keeping any heavy rainfall under 5 minutes or less in duration for the most part. Training of thunderstorm cells will produce the greatest risk for extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding.
-	Stronger thunderstorm activity today is expected to favor I-70 northward. Strong thunderstorms may also become severe with gusty winds and large hail being the primary threats.

STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce a 0.1-0.3". Strong thunderstorms will have the potential to produce 0.2-0.6" in 10-20 minutes. Note* - Due to fast storm motions we are using 20-minute rain totals today in the table for the first time this season.

WORST CASE SCENARIO: Training of moderate to strong thunderstorm cells may result in up to 1.8" of heavy rainfall in 45-60 minutes.

County	Message	Valid Times	Prime Time
the City of Aurora	1	Current TO 600 PM	1200 PM TO 500 PM
Arapahoe County	1	Current TO 600 PM	1200 PM TO 500 PM
DIA	1	Current TO 600 PM	1200 PM TO 500 PM
Denver County	1	Current TO 600 PM	1200 PM TO 500 PM
Adams County	1	Current TO 600 PM	1200 PM TO 500 PM
Broomfield County	1	Current TO 600 PM	1200 PM TO 500 PM
Jefferson County	1	Current TO 600 PM	1200 PM TO 500 PM
Boulder County	1	Current TO 600 PM	1200 PM TO 500 PM
Arvada	1	Current TO 600 PM	1200 PM TO 500 PM
Wheat Ridge	1	Current TO 600 PM	1200 PM TO 500 PM
Lakewood	1	Current TO 600 PM	1200 PM TO 500 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	20-Minute Rainfall and % Probability	Message Potential
Plains
Adams	Current TO 600 PM THU	0.1" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Arapahoe	Current TO 600 PM THU	0.1" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Boulder	Current TO 600 PM THU	0.1" (95%) to 0.3" (65%) to 0.6" (35%)	ISSUED
Broomfield	Current TO 600 PM THU	0.1" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Denver	Current TO 600 PM THU	0.1" (80%) to 0.3" (50%) to 0.6" (25%)	ISSUED
Douglas	Current TO 600 PM THU	0.1" (60%) to 0.3" (40%) to 0.6" (20%)	MOD
Jefferson	Current TO 600 PM THU	0.1" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 600 PM THU	0.1" (100%) to 0.3" (75%) to 0.6" (35%)	ISSUED
Douglas	Current TO 600 PM THU	0.1" (65%) to 0.3" (40%) to 0.6" (20%)	MOD
Jefferson	Current TO 600 PM THU	0.1" (100%) to 0.3" (75%) to 0.6" (35%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.