Time: 956 AM Tue June 18, 2024 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Cooler temperatures and isolated thunderstorms today The heat wave has finally shifted east this morning, thanks to the arrival of an upper-level trough and its associated cold front. Temperatures will reach the mid to upper 70s with slight chances for isolated showers and thunderstorms developing by the afternoon. Dewpoints will be in the mid 30s, with precipitable water (PWAT) values between 0.50”-0.60”. Storms will be capable of producing light rainfall, with better chances across the foothills. Storm motions will be from southwest to northeast between 15-20 mph. Thunderstorms are expected to dissipate by mid evening with skies remaining partly cloudy overnight. STORM RAINFALL POTENTIAL AND DURATION: Typical storms will produce a trace to 0.10” in 10-30 minutes. WORST CASE SCENARIO: Slow moving or training thunderstorms may be capable of producing up to 0.50” in 45-60 minutes. A LOOK AHEAD: A more active pattern emerges tomorrow as elevated moisture levels and favorable upper-level winds support chances for scattered thunderstorms. Storms are expected to continue into the evening, with a few isolated showers possible overnight. An expanding and near-stationary heat dome over the east coast will force the upper-level trough to reposition over the Great Basin on Thursday. As a result, a warmer airmass and moisture from the Gulf of Mexico will advect (transport) into the four-corners region. Elevated moisture levels and favorable upper-level winds from the southwest will support afternoon and evening scattered thunderstorms across the High Plains on Thursday, with a few storms capable of producing brief heavy rain. There is still some uncertainty about the exact timing and precipitation amounts, which will depend on the behavior of the heat wave over the eastern US. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Arapahoe 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Boulder 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Broomfield 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Denver 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Douglas 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Jefferson 300 PM TO 1000 PM Trace (35%) to 0.05" (25%) to 0.1" (15%) NONE Foothills above 6500ft       Boulder 200 PM TO 1100 PM Trace (45%) to 0.05" (35%) to 0.1" (25%) NONE Douglas 200 PM TO 1100 PM Trace (45%) to 0.05" (35%) to 0.1" (25%) NONE Jefferson 200 PM TO 1100 PM Trace (45%) to 0.05" (35%) to 0.1" (25%) 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]