Time: 901 AM Mon August 2, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- THE PLAINS MAY SQUEEZE OUT ANOTHER DRY DAY WHILE THUNDERSTORMS RETURN TO THE HIGHER TERRAIN - Plume of monsoon moisture lurks to the west and will result in thunderstorms developing over the mountains and higher foothills this afternoon. Upper level steering winds will keep the majority of the activity over the mountains with possibly a late afternoon or evening rain shower/thunderstorm developing over western areas of the District. Most areas over the plains likely squeeze out another dry day... - Between 2-4pm shower and thunderstorm activity is expected to begin to develop W of the District. Outflow from storms to the W may push eastward and result in shower and thunderstorm initiation in or near the District between 4-8pm. A slight chance for isolated showers and weak thunderstorms will continue through about midnight. If shower/weak thunderstorm activity is able to develop it is expected to favor areas W of I-25 and in particular in/near the foothills. - Haze will continue to plague visibilities today but overall skies will be mostly sunny to partly cloudy through the afternoon becoming mostly cloudy late. Temperatures will warm into the 80's over the plains with 70's in the Front Range foothills. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.2" of rain. Weak thunderstorms will have the potential to produce 0.2-0.5" in 10-30 minutes. WORST CASE SCENARIO: The monsoon moisture pushes further E than anticipated increasing moisture and resulting in moderate to strong thunderstorms late this afternoon and evening with the potential to produce 0.5-1.5" of heavy rain in 10-30 minutes. A LOOK AHEAD: The monsoon moisture plume is anticipated to move over the District on Tuesday and Wednesday. Tuesday is expected to be the more active day but Wednesday may surprise to the upside? Thunderstorms that develop in the afternoon will have the potential to produce heavy rainfall that may lead to excessive runoff and possibly flash flooding. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 600 PM TO 1000 PM Trace (30%) to 0.2" (15%) to 0.5" (5%) NONE Arapahoe 600 PM TO 1000 PM Trace (30%) to 0.2" (15%) to 0.5" (5%) NONE Broomfield 600 PM TO 1000 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Denver 600 PM TO 1000 PM Trace (30%) to 0.2" (15%) to 0.5" (5%) NONE Boulder 500 PM TO 1000 PM Trace (50%) to 0.2" (20%) to 0.5" (10%) LOW Douglas 500 PM TO 1000 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Jefferson 500 PM TO 1000 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 300 PM TO 1000 PM Trace (80%) to 0.2" (60%) to 0.5" (30%) MOD Douglas 300 PM TO 1000 PM Trace (80%) to 0.2" (60%) to 0.5" (30%) MOD Jefferson 300 PM TO 1000 PM Trace (80%) to 0.2" (60%) to 0.5" (30%) 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]