Flash Flood Prediction Program

-	Thunderstorm chances increase today as NW flow aloft continues while surface moisture has increased, and a passing upper level disturbance will help to initiate thunderstorms during the afternoon. Although thunderstorms are only expected to be isolated to widely scattered in coverage the storms that do develop will have the potential to become strong to severe, potentially producing heavy rainfall.
-	Thunderstorms will first develop over the mountains and foothills by 1-2pm, moving onto the I-25 corridor between 3-4pm. Storms will be fast moving from NW to SE at 25-30mph helping to reduce point rainfall amounts from a single storm but brief heavy rainfall is likely from stronger storms. Large thunderstorms or training of thunderstorm cells will have the greatest threat for heavy rainfall exceeding more than 10 minutes in duration.
-	Strong thunderstorms also have a high likelihood of becoming severe with large hail and gusty straight-line winds being the primary threats. Conditions are expected to dry out by around sunset or shortly after.

STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak to moderate thunderstorms will produce a trace to 0.3". Moderate to strong thunderstorms will have the potential to produce 0.3-0.9" in 10-30 mintues. Supplemental QPF is available at https://qpf.udfcd.org

WORST CASE SCENARIO: A large, slower moving thunderstorm or training of thunderstorm cells may produce rainfall amounts of up to 1.6" in 45-60 minutes.

A LOOK AHEAD: Not much change for Monday with widely scattered afternoon thunderstorms some of which may become strong to severe and contain brief heavy rainfall.

Location	Prime Time	30-Minute Rainfall and % Probability	Message Potential
Plains
Adams	300 PM TO 900 PM	Trace (80%) to 0.3" (50%) to 0.9" (10%)	LOW
Arapahoe	300 PM TO 900 PM	Trace (85%) to 0.3" (60%) to 0.9" (15%)	MOD
Boulder	300 PM TO 900 PM	Trace (80%) to 0.3" (50%) to 0.9" (10%)	LOW
Broomfield	300 PM TO 900 PM	Trace (80%) to 0.3" (50%) to 0.9" (10%)	LOW
Denver	300 PM TO 900 PM	Trace (80%) to 0.3" (50%) to 0.9" (10%)	LOW
Douglas	300 PM TO 900 PM	Trace (85%) to 0.3" (60%) to 0.9" (15%)	MOD
Jefferson	300 PM TO 900 PM	Trace (85%) to 0.3" (60%) to 0.9" (15%)	MOD
Foothills above 6500ft
Boulder	200 PM TO 800 PM	Trace (90%) to 0.3" (60%) to 0.9" (10%)	LOW
Douglas	200 PM TO 800 PM	Trace (90%) to 0.3" (60%) to 0.9" (15%)	MOD
Jefferson	200 PM TO 800 PM	Trace (90%) to 0.3" (60%) to 0.9" (15%)	MOD

MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.