Flash Flood Prediction Program

Time: 914 AM Mon July 5, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- UPPER LEVEL DISTURBANCE TO INCREASE THUNDERSTORM ACTIVITY TODAY - A passing upper level disturbance is expected to increase the thunderstorm activity today over the District. Ample moisture remains at the surface to fuel storms and in tandem with daytime heating thunderstorms will once again develop over the higher terrain to the W of the District by around noon. - Thunderstorm chances will increase over the plains between 1-3pm. Prime time for stronger thunderstorms will be between 3-9pm. An additional round of showers and possibly a weak thunderstorm continues likely until midnight with a few lingering isolated light rain showers into early Tuesday morning. Thunderstorms that develop today will be very capable of producing moderate to heavy rainfall and may become severe with large hail and gusty winds being the primary threats. - Upper level steering winds remain relatively light from NW to SE at 10-15mph. Outflow boundaries and gust fronts may act to slow down or briefly anchor storms and may result in erratic storm motions at times. Temperatures today expected to reach the lower 90's over the plains. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.4" of rainfall. Strong thunderstorms will have the potential to produce 0.4-1.2" in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.5" of heavy rain in 45-60 minutes. A LOOK AHEAD: Behind the disturbance on Tuesday temperatures will be cooler in the upper 70's to lower 80's for highs. The best chances for thunderstorms will be pushed southward but there will still be widely scattered afternoon thunderstorms with the potential to produce heavy rainfall. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Arapahoe 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Broomfield 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Denver 300 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Boulder 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Douglas 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Jefferson 200 PM TO 900 PM 0.1" (90%) to 0.4" (60%) to 1.2" (30%) HIGH Foothills above 6500ft       Boulder 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (30%) HIGH Douglas 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (30%) HIGH Jefferson 100 PM TO 900 PM 0.1" (95%) to 0.4" (65%) to 1.2" (30%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]