Flash Flood Prediction Program

Message 1’s have been issued for the entire District effective until 8:00pm as the threat for heavy rainfall with the potential for severe storms across the District this afternoon and early evening.

The best chance for any shower/thunderstorm activity within the District will be between noon-8pm with a few lingering showers possible through 10pm. The best chance for heavy rainfall will be during the initial round of storms, with storm intensities decreasing into the evening hours. Storm motions will be west to east between 20-25mph which should also limit point rainfall amounts. However, outflow boundaries could produce erratic storm movement which will increase chances for brief heavy rainfall.

Good upper-level support suggests at least a moderate chance for severe weather today, mainly for gusty winds 60+ mph and hail up to 1.0” in diameter likely favoring areas east of I-25. Severe storms will also contain isolated heavy rainfall with the largest threat being a quick 0.5” in 10-15min rather than any long-lasting heavy rainfall. Skies will clear this evening with dry conditions expected through the overnight as temperatures drop into the mid to upper 50s on the plains with upper 40s to around 50 degrees along the foothills.

STORM RAINFALL POTENTIAL AND DURATION: Typical showers and isolated thunderstorms will produce a 0.05-0.30” total in 10-30 minutes. A moderate to strong/severe shower/thunderstorm will produce 0.30-0.60” total in 10-30 minutes.

WORST CASE SCENARIO: A strong, stationary thunderstorm, or training of thunderstorm cells will have the potential to produce up to 1.20” total in under 60 minutes.

County	Message	Valid Times	Prime Time
Arvada	1	1200 PM TO 800 PM	100 PM TO 700 PM
the City of Aurora	1	1200 PM TO 800 PM	100 PM TO 700 PM
Denver County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Arapahoe County	1	1200 PM TO 800 PM	100 PM TO 700 PM
DIA	1	1200 PM TO 800 PM	100 PM TO 700 PM
Adams County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Douglas County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Broomfield County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Jefferson County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Boulder County	1	1200 PM TO 800 PM	100 PM TO 700 PM
Wheat Ridge	1	1200 PM TO 800 PM	100 PM TO 700 PM
Lakewood	1	1200 PM TO 800 PM	100 PM TO 700 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Arapahoe	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Boulder	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Broomfield	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Denver	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Douglas	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Jefferson	1200 PM TO 800 PM	0.05" (90%) to 0.3" (60%) to 0.6" (30%)	ISSUED
Foothills above 6500ft
Boulder	1200 PM TO 800 PM	0.05" (70%) to 0.3" (35%) to 0.6" (15%)	ISSUED
Douglas	1200 PM TO 800 PM	0.05" (70%) to 0.3" (35%) to 0.6" (15%)	ISSUED
Jefferson	1200 PM TO 800 PM	0.05" (70%) to 0.3" (35%) to 0.6" (15%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.