Flash Flood Prediction Program

The active pattern has mostly passed for the time being, and chances of measurable rainfall decrease today and for the most of the work week. The southwestern US ridge has begun its slow return to Colorado, and northerly flow has delivered a drier airmass from the Great Basin to the District today. Morning dewpoints in the low 50s are forecasted to mix down to the low 40s by the time isolated seasonal convection starts over the high country west of the District. Storms that reach the foothills and plains in and around the District will have 0.7”-0.8” inches of precipitable water (PWAT) to work with, and will be capable of brief thunderstorm downpours of 0.25”-0.50” in 10-30 minutes, moving from NNW to SSE at 10-15mph. Forecast model guidance suggests that storms in the District today are unlikely, but enough residual moisture and energy remains in the atmosphere that the District will have a LOW probability of message issuance during a window between 1pm and 8pm.

STORM RAINFALL POTENTIAL AND DURATION: Typical showers and thunderstorms will produce 0.25"-0.50" in 10-30 minutes. Stronger storms at higher elevations may produce 0.75" in 10-30 minutes.

WORST CASE SCENARIO: A slow-moving or stationary shower or thunderstorm may be capable of producing 1.00" in 30 minutes or less.

A LOOK AHEAD: The warming and drying trend continues tomorrow, and the probability of message issuance will likely be NONE. There is a small uptick in moisture as temperatures continue to warm Wednesday; likely dry Thursday before moisture returns this weekend.

Location	Prime Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Arapahoe	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Boulder	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Broomfield	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Denver	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Douglas	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Jefferson	100 PM TO 800 PM	Trace (30%) to 0.3" (20%) to 0.5" (10%)	LOW
Foothills above 6500ft
Boulder	100 PM TO 800 PM	0.1" (30%) to 0.3" (20%) to 0.8" (10%)	LOW
Douglas	100 PM TO 800 PM	0.1" (30%) to 0.3" (20%) to 0.8" (10%)	LOW
Jefferson	100 PM TO 800 PM	0.1" (30%) to 0.3" (20%) to 0.8" (10%)	LOW

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.