Time: 844 AM Thu July 28, 2022 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH A GOOD CHANCE FOR HEAVY RAINFALL PRODUCING THUNDERSTORMS/EXCESSIVE RUNOFF LIKELY - Another overnight round of heavy rainfall and isolated thunderstorms impacted the District with a few linger light rain showers currently. These light rain showers will continue to taper off through the morning with cloudy to partly cloudy skies likely throughout the day leading to high temperatures to only reach the 70's this afternoon. - The NWS has issued a Flash Flood Watch for Boulder County from 11am today until 10pm this evening above 6,000ft. This Flash Flood Watch will result in Message 2's being issued for Boulder County from 11am to 10pm to sync with the NWS. Message 1's will be issued for all Counties effective at 11am until 10pm to coincide with the Message 2's as the threat for heavy rainfall will include the entire District at this time. - Thunderstorms will first initiate over the mountains and foothills W of the District between 10am and noon. Upper-level steering winds from W to E at 5-10mph will slowly push the storms eastward onto the plains between noon and 1 or 2pm. Prime time for wetting rain showers and moderate to strong thunderstorms will be from 1pm to 10pm. Multiple rounds (2-3) of storms are possible through the afternoon into the early evening. Moderate to strong thunderstorms that develop today will be efficient rainfall producers as moisture levels are very high for Colorado standards. Even moderate thunderstorms will have the potential to produce heavy rainfall and strong thunderstorms will be very capable of producing heavy downpours that may lead to excessive runoff and flash flooding. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.3-1.0" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 1.0-2.0" in 10-30 minutes. WORST CASE SCENARIO: A strong anchored thunderstorm or a slower moving large thunderstorm may result in rainfall rates up to 3.0" in 45-75 minutes. A LOOK AHEAD: Not much change in the overall pattern heading into Friday. Low-level moisture will still be abundant and with slightly warmer temperatures the threat for heavy rainfall will likely continue at least for Friday and possible into Saturday before drier air finally moves in this weekend. However, a chance will remain Saturday afternoon and evening for rain showers/isolated thunderstorms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Arapahoe 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Boulder 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Broomfield 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Denver 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Douglas 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Jefferson 1200 PM TO 1000 PM 0.3" (90%) to 1.0" (45%) to 2.0" (20%) HIGH Foothills above 6500ft       Boulder 1200 PM TO 1000 PM 0.3" (95%) to 1.0" (50%) to 2.0" (25%) HIGH Douglas 1200 PM TO 1000 PM 0.3" (95%) to 1.0" (50%) to 2.0" (25%) HIGH Jefferson 1200 PM TO 1000 PM 0.3" (95%) to 1.0" (50%) to 2.0" (25%) 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]