Time: 824 AM Sun June 13, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT AND GENERALLY DRY BUT IF A THUNDERSTORM DEVELOPS IT COULD BECOME STRONG WITH THE POTENTIAL FOR HEAVY RAINFALL - A boom or bust kind of day for thunderstorm activity over the District today as low level moisture has advected into the area and if it lingers into the afternoon it could fuel strong thunderstorms... Additionally, a warm layer of air aloft will need to be overcome for storms to form and conditions may very well end up dry. What is certain is that our temperatures will be warming further with highs well into the 90's over the plains. - The most likely outcome for today is that storms develop to the S of the District over the Palmer Divide and travel eastward with no impact within the District itself and conditions remain dry. Although less likely, but certainly possible is the storms that develop over the Palmer Divide produce a rain cooled gust front that moves northward into the District which acts a trigger helping to overcome the warm layer of air aloft and produce thunderstorms. - If surface moisture remains elevated with dew points in the 50's and the warm layer of air aloft is overcome, thunderstorms that develop today will be capable of producing heavy rainfall. Thunderstorms will be slow moving from W to E at 10mph or less but may move erratically along gust fronts/outflow boundaries. The end result is low chances for storms with high potential rainfall amounts favoring areas S and E areas of the District. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce a trace to 0.3" of rain. Strong thunderstorms will have the potential to produce 0.3-0.9" of rain in 10-30 minutes. WORST CASE SCENARIO: Moisture levels remain elevated with strong/slow moving thunderstorms having the potential to produce up to 1.8" in 45-60 minutes. A LOOK AHEAD: The heat wave intensifies on Tuesday with temperatures reaching the mid 90's to around 100 degrees over the plains. Temperatures will peak on Tuesday in the upper 90's to lower 100's. Dry conditions are expected both days. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM Trace (30%) to 0.3" (15%) to 0.8" (5%) LOW Arapahoe 300 PM TO 900 PM Trace (30%) to 0.3" (15%) to 0.8" (5%) LOW Boulder 300 PM TO 900 PM Trace (20%) to 0.3" (10%) to 0.8" (5%) NONE Broomfield 300 PM TO 900 PM Trace (20%) to 0.3" (10%) to 0.8" (5%) NONE Denver 300 PM TO 900 PM Trace (30%) to 0.3" (15%) to 0.8" (5%) LOW Douglas 300 PM TO 900 PM Trace (60%) to 0.3" (30%) to 0.8" (10%) LOW Jefferson 300 PM TO 900 PM Trace (30%) to 0.3" (15%) to 0.8" (5%) NONE Foothills above 6500ft       Boulder 200 PM TO 900 PM Trace (30%) to 0.3" (10%) to 0.8" (5%) NONE Douglas 200 PM TO 900 PM Trace (75%) to 0.3" (40%) to 0.8" (10%) LOW Jefferson 200 PM TO 900 PM Trace (50%) to 0.3" (20%) to 0.8" (10%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]