Flash Flood Prediction Program

Time: 831 AM Sat July 17, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT WITH ANOTHER CHACE FOR ISOLATED RAIN SHOWERS/THUNDERSTORMS THIS AFTERNOON AND EARLY EVE - Not much has changed in the overall pattern over the Colorado region today with mostly sunny skies to start the morning which will help temperatures increase into the upper 80's to mid 90's across the plains this afternoon with low to mid 80's along the foothills. Similar conditions as yesterday with a chance for afternoon rain showers and isolated thunderstorms. Currently dew points are in the low to mid 50's and should slowly mix out through the morning, however, if dew points stay elevated into the afternoon there will be a better chance for rain showers and thunderstorms along the I-25 corridor this afternoon with the potential for isolated heavy rainfall favoring areas east of I-25 at this time. - Storms today will initiate along the higher terrain in the foothills and along the Palmer Divide around midday and will progress from W to E between 10-15mph. Best chance for isolated rain showers/thunderstorms in the District will be this afternoon between 2-4pm with storms increasing in intensity as they move out onto the eastern plains and away from the District. A slight chance for an outflow boundary that moves westerly from strong storms out on the eastern plains which will have the potential to trigger additional storms within the District between 4-8pm. These additional storms could have the potential for brief moderate to heavy rainfall as any storm development along outflow boundaries will move erratically if not remain stationary for an extended period increasing chances for isolated heavy rainfall. Any storm development should quickly decrease around sunset with mild and dry conditions through the rest of the evening. - Skies will gradually clear completely through the rest of the evening with overnight lows dropping into the low to mid 60's on the plains with mid to upper 50's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce a trace-0.2" of rainfall in 10-30 minutes. A moderate to strong thunderstorms will produce 0.2-0.4" of rainfall in 10-30 minutes. WORST CASE SCENARIO: A moderate to strong stationary thunderstorm formed along an outflow boundary has the potential to produce 1.0" in 45-60 minutes. A LOOK AHEAD: The high-pressure ridge will return over the next several days resulting in high temperatures in the low to mid 90's across the plains through next week. A very slight chance each afternoon and early evening for rain showers/isolated thunderstorms, however, at this time, little to no threat for heavy rainfall is expected through the week as surface moisture starts to decrease along with less mid to upper-level moisture as well. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (20%) LOW Arapahoe 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (20%) LOW Boulder 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (15%) LOW Broomfield 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (15%) LOW Denver 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (15%) LOW Douglas 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (20%) LOW Jefferson 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (15%) LOW Foothills above 6500ft       Boulder 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (10%) NONE Douglas 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (10%) NONE Jefferson 200 PM TO 800 PM Trace (50%) to 0.2" (30%) to 0.4" (10%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]