Flash Flood Prediction Program

Storms have already started to impact portions of the foothills just outside of the District. The best chance for storm activity within the District will begin over the next hour with a chance for storms lasting into the evening hours. Storm motions will generally be west to east between 10-15mph, with some erratic storm motions likely from outflow boundaries. This will result in some storms having the potential to anchor in place with a threat for moderate to heavy rainfall. A quick 0.50”-0.80” in 10-30 minutes is expected rather than any long lasting rainfall. Storms today may also contain hail up to 1.0”, gusty winds up to 50mph and frequent cloud-to-ground lightning. A slight chance of showers lingers past sundown, although the threat of heavy rainfall will likely subside by 8-9pm this evening. Overnight temperatures will drop into the low 60s for the plains with mid to upper 50s along the foothills.

STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce 0.05-0.30" total in 10-30 minutes. A moderate to strong thunderstorm will produce rainfall rates of 0.30”-0.80” total in 10-
30 minutes.

WORST CASE SCENARIO: A slow-moving thunderstorm, training of thunderstorms cells or a large
thunderstorm complex may result in up to 1.20” of rain in 30-60 minutes.

County	Message	Valid Times	Prime Time
Boulder County	1	Current TO 900 PM	Current TO 830 PM
Jefferson County	1	Current TO 900 PM	Current TO 830 PM
Broomfield County	1	Current TO 900 PM	Current TO 830 PM
Douglas County	1	Current TO 900 PM	Current TO 830 PM
Adams County	1	Current TO 900 PM	Current TO 830 PM
Denver County	1	Current TO 900 PM	Current TO 830 PM
DIA	1	Current TO 900 PM	Current TO 830 PM
Arapahoe County	1	Current TO 900 PM	Current TO 830 PM
the City of Aurora	1	Current TO 900 PM	Current TO 830 PM
Arvada	1	Current TO 900 PM	Current TO 830 PM
Wheat Ridge	1	Current TO 900 PM	Current TO 830 PM
Lakewood	1	Current TO 900 PM	Current TO 830 PM

County-specific Quantitative Precipitation Outlook	Precipitation Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Arapahoe	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Boulder	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Broomfield	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Denver	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Douglas	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Jefferson	Current TO 900 PM SAT	0.05" (60%) to 0.3" (30%) to 0.8" (15%)	ISSUED
Foothills above 6500ft
Boulder	Current TO 900 PM SAT	0.05" (75%) to 0.3" (50%) to 0.8" (25%)	ISSUED
Douglas	Current TO 900 PM SAT	0.05" (75%) to 0.3" (50%) to 0.8" (25%)	ISSUED
Jefferson	Current TO 900 PM SAT	0.05" (75%) to 0.3" (50%) to 0.8" (25%)	ISSUED

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.