Flash Flood Prediction Program

-	Mid and upper level monsoon moisture will move overhead today and result in thunderstorm activity returning to the District. Thunderstorms that develop will be slow moving and have the potential to produce heavy rainfall that may lead to excessive runoff and possibly flash flooding.
-	Thunderstorms will develop over the mountains/foothills during the early afternoon. Thunderstorm chances increase over the plains between 2-3pm with prime time from 3-9pm. Additional showers and weaker thunderstorms will remain possible until midnight. 1-2 rounds of thunderstorms are expected with the initial round likely being the strongest.
-	Relatively slow storm motions from W to E at around 10mph will allow for extended periods of heavy rain under stronger storms. Storm motions may become erratic at times due to outflow boundaries/gust front interactions.

STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.2-0.6" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes.

WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 3.0" in 60 minutes or less.

A LOOK AHEAD: Ridge of high pressure shifts back to the west on Thursday decreasing the chances for thunderstorms over the plains as the activity moves back over the mountainous areas of the state. There will still be a chance for isolated afternoon thunderstorm activity favoring the W and S areas of the District. Heavy rainfall threat lowers considerably.

Location	Prime Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	300 PM TO 900 PM	0.2" (75%) to 0.6" (50%) to 1.8" (25%)	HIGH
Arapahoe	300 PM TO 900 PM	0.2" (75%) to 0.6" (50%) to 1.8" (25%)	HIGH
Broomfield	300 PM TO 900 PM	0.2" (75%) to 0.6" (50%) to 1.8" (25%)	HIGH
Denver	300 PM TO 900 PM	0.2" (75%) to 0.6" (50%) to 1.8" (25%)	HIGH
Boulder	200 PM TO 900 PM	0.2" (80%) to 0.6" (50%) to 1.8" (25%)	HIGH
Douglas	200 PM TO 900 PM	0.2" (80%) to 0.6" (50%) to 1.8" (25%)	HIGH
Jefferson	200 PM TO 900 PM	0.2" (80%) to 0.6" (50%) to 1.8" (25%)	HIGH
Foothills above 6500ft
Boulder	100 PM TO 900 PM	0.2" (90%) to 0.6" (60%) to 1.8" (30%)	HIGH
Douglas	100 PM TO 900 PM	0.2" (90%) to 0.6" (60%) to 1.8" (30%)	HIGH
Jefferson	100 PM TO 900 PM	0.2" (90%) to 0.6" (60%) to 1.8" (30%)	HIGH

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.