Time: 858 AM Mon June 28, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- CONTINUED UNSEASONABLY COOL WITH LESS NUMEROUS SHOWERS AND THUNDERSTORMS FAVORING THE FOOTHILLS - Temperatures will remain below seasonal averages over the District today with highs in the 70's over the plains and 60's in the Front Range foothills. Normal high for Denver today is 87 degrees. Rain showers and isolated to widely scattered thunderstorms are expected this afternoon, however the shower and thunderstorm coverage is expected to be less than previous days as moisture has decreased a bit from this time yesterday. - Rain showers and weak thunderstorms will become possible before noon, mainly in and near the foothills. Upper level steering winds at around 15mph from N to S through early afternoon and NW to SE later this afternoon is expected to keep the majority of the storm activity over the foothills. Over the plains the best chances for storms will be along and W of I-25 and S of I-70 with far NE areas of the District expected to have the lowest chance for storm activity today. - Thunderstorm strength this afternoon will hinge upon daytime heating with weak to moderate thunderstorms currently expected and temperatures reaching the low to mid 70's. Should temperatures warm more than anticipated into the upper 70's stronger thunderstorms may develop and there will be a better chance for heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" of rain. Moderate to briefly strong thunderstorms will have the potential to produce 0.2-0.6" in 10-30 minutes. WORST CASE SCENARIO: Temperatures warm further than anticipated resulting in strong thunderstorms with the potential to produce 0.4-1.2" of rain in 10-30 minutes and up to 2.0" in 45-60 minutes. A LOOK AHEAD: A similar outlook on Tuesday with isolated to widely scattered afternoon thunderstorms and temperatures in the 70's for highs. A low threat for heavy rainfall is expected. We add more heat and moisture into the equation from Wednesday through Friday resulting in a moderate to high threat for heavy rainfall producing thunderstorms each day, likely peaking on Friday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 1000 PM 0.1" (60%) to 0.3" (30%) to 0.6" (10%) LOW Arapahoe 100 PM TO 1000 PM 0.1" (70%) to 0.3" (50%) to 0.6" (20%) LOW Broomfield 100 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Denver 100 PM TO 1000 PM 0.1" (70%) to 0.3" (50%) to 0.6" (20%) LOW Boulder 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Douglas 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Jefferson 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Foothills above 6500ft       Boulder 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) MOD Douglas 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) MOD Jefferson 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) 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]