Time: 827 AM Fri June 2, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- MOSTLY SUNNY AND MILD CURRENTLY WITH ANOTHER CHANCE FOR AFTERNOON AND EVENING SHOWERS/THUNDERSTORMS A minimal change to the overall pattern today as an active weather pattern has stalled out of the Colorado region and will continue to do so over the next several days. A few dynamics have changed for today with slightly more sunshine this morning, with slightly lower dew points at the surface than yesterday which are currently in the mid to upper 40’s. However, the added sunshine will suggest a better chance for daytime heating leading to the possibility for stronger storms, especially along the far eastern plains. Dew points are slightly less, which could help limit heavier rainfall if they are able to drop into the low to mid 40’s this afternoon. Showers and thunderstorms are expected to initiate along the higher terrain around midday with the best chance for impactful storms in the District between 1-9pm. Storm motions will generally be south to north between 5-10mph, with erratic storm motions likely for storms formed along outflow boundaries. These outflow storms will also have the highest chance for localized heavy rainfall, with the largest threat today being a quick 0.5” in 10-15min, rather than any long-lasting heavy rainfall. However, a long-lasting heavy shower cannot be completely ruled out if a stronger storm can anchor for an extended period today. Similar to yesterday/last night, another chance for some isolated overnight rain showers with a few rumbles of thunder will be possible; however, the threat of heavy rainfall should subside later this evening. Overnight lows will drop into the upper 40’s to low 50’s on the plains with mid 40’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.3” of rain in 10-30 minutes. Strong thunderstorms will have the potential to produce rainfall rates of 0.3-0.7” in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm formed along an outflow boundary may result in up to 1.4” of rain in 45-75 minutes. A LOOK AHEAD: Cooler and cloudy tomorrow will result in temperatures playing a big part in the heavy rainfall threat as temperatures are not expected to reach 70 degrees. This should help limit stronger storm development as minimal sunshine expected to enhance daytime heating. A good chance will remain for showers and an isolated thunderstorm with likely a LOW to MOD chance for Message 1’s to be issued since an abundance of moisture will be available both at the surface and aloft. These conditions remain in place Sunday with another chance for shower activity throughout the day, once again hinging on whether or not there is enough daytime heating to get stronger storms to develop. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (15%) MOD Arapahoe 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (15%) MOD Boulder 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (10%) LOW Broomfield 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (10%) LOW Denver 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (10%) LOW Douglas 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (15%) MOD Jefferson 100 PM TO 900 PM 0.1" (70%) to 0.3" (35%) to 0.7" (10%) LOW Foothills above 6500ft       Douglas 100 PM TO 900 PM 0.1" (75%) to 0.3" (50%) to 0.7" (15%) MOD Jefferson 100 PM TO 900 PM 0.1" (75%) to 0.3" (50%) to 0.7" (15%) MOD Boulder 1200 PM TO 800 PM 0.1" (75%) to 0.3" (50%) to 0.7" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]