Flash Flood Prediction Program

Time: 937 AM Sat June 25, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER WITH SHOWERS/THUNDERSTORMS FAVORING THE EVENING HOURS/HIGHER TERRAIN - A cold front has moved through this morning and is resulting in cloud cover which will help to keep temperatures below normal in the lower 70's over the plains with 60's in the Front Range foothills. Multiple ingredients are in play for thunderstorms with the potential for heavy rainfall today but the strength of storms today will hinge upon daytime heating and that factor is limited. - With cloud cover early thunderstorm development will hold off until mid afternoon most areas with the majority of the storm activity focusing in the evening and early overnight hours. Between 1-3pm shower and thunderstorms are expected to initiate over the western foothills and Palmer Divide. Showers and isolated to widely scattered thunderstorms will then fill in over the plains between 3-5pm. Best chances for light to moderate rain showers and thunderstorms will be through about midnight. Storms will move from WSW to ENE at around 15mph. Some storms may move erratically due to outflow boundary/gust front interactions. Additional, light rain showers continue likely overnight. - The current thinking is that the clouds over the plains will decrease the intensity of storms over the majority of the District with the greatest threat for moderate to strong thunderstorms with heavy rainfall over the foothills and higher terrain of the Palmer Divide on the W and S District fringes. If temperatures warm further than expected due to more sunshine earlier in the day the threat for heavy rainfall will spread out onto the plains. To summarize, there is the potential for heavy rainfall today but it is far from certain whether any of the stronger storms will be able to impact the District. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.2" in 10-30 minutes. Weak to moderate thunderstorms will produce 0.2-0.6" in 10-30 minutes. Strong thunderstorms if able to develop will have the potential to produce up to 1.2" in 30 minutes or less. WORST CASE SCENARIO: Temperatures warm more than expected resulting in strong thunderstorms with the potential to produce heavy rainfall rates of 0.6-1.8" in 15-45 minutes. A LOOK AHEAD: Temperatures will remain on the fool side Sunday with highs around 70 degrees over the plains. There will be a slight chance for a few lingering light rain showers into Sunday morning with thunderstorms becoming possible in the afternoon. Much like today the best chances for thunderstorms will be over the foothills and Palmer Divide with lesser chances over the plains. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 200 AM SUN Trace (90%) to 0.3" (40%) to 0.6" (15%) LOW Arapahoe 300 PM TO 200 AM SUN Trace (95%) to 0.3" (50%) to 0.6" (20%) LOW Broomfield 300 PM TO 200 AM SUN Trace (95%) to 0.3" (50%) to 0.6" (20%) LOW Denver 300 PM TO 200 AM SUN Trace (95%) to 0.3" (50%) to 0.6" (20%) LOW Boulder 200 PM TO 200 AM SUN Trace (95%) to 0.3" (50%) to 0.6" (20%) LOW Douglas 200 PM TO 200 AM SUN Trace (100%) to 0.3" (60%) to 0.6" (30%) LOW Jefferson 200 PM TO 200 AM SUN Trace (95%) to 0.3" (50%) to 0.6" (20%) LOW Foothills above 6500ft       Boulder 100 PM TO 200 AM SUN Trace (100%) to 0.3" (60%) to 0.6" (30%) LOW Douglas 100 PM TO 200 AM SUN Trace (100%) to 0.3" (75%) to 0.6" (50%) MOD Jefferson 100 PM TO 200 AM SUN Trace (100%) to 0.3" (75%) to 0.6" (50%) 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]