Flash Flood Prediction Program

Time: 900 AM Sat August 19, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER HOT DAY WITH A CHANCE FOR A FEW AFTERNOON SHOWERS/ISOLATED THUNDERSTORMS A southwesterly flow aloft will continue to dominate over the region today ahead of another weak disturbance that will move north of the region this afternoon and evening. This weak disturbance will bring a chance for a few showers/isolated thunderstorms starting between 1-2pm for the higher terrain foothills with a few showers/isolated thunderstorms possible in the District between 2-7pm, with chances likely tapering off by 8pm. Storms today will favor areas north of I-70, however a few showers/isolated thunderstorms will be possible for areas south, along the I-25 corridor and into the Douglas County area. Typical storm motions will be from the SW to NE, between 10-15mph, once again helping limit point rainfall amounts. Although, storms today will have the potential to produce outflow boundaries with some slower moving storms along these boundaries. Dew points will likely remain in the low to mid 50s through the morning, which will result in at least a LOW chance for Message 1s to be issued, mainly for the threat of a quick 0.5” in 10-15min from any outflow boundary induced storms. Overnight will be breezy and dry with lows dropping into the 60s on the plains with upper 50s in the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a TR-0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.50” total in 10-30 minutes. WORST CASE SCENARIO: A strong, stationary thunderstorm, or training of thunderstorm cells will have the potential to produce 0.50-1.00” total in under 60 minutes. A LOOK AHEAD: Conditions start to dry out on Sunday as high temperatures remain in the 90s with breezy winds under mostly sunny skies. Similar conditions remain in place Monday & Tuesday, breezy and dry as high temperatures continue to reach into the 90s. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 800 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Arapahoe 200 PM TO 800 PM Trace (50%) to 0.25" (25%) to 0.5" (10%) LOW Boulder 200 PM TO 800 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Broomfield 200 PM TO 800 PM Trace (60%) to 0.25" (30%) to 0.5" (15%) LOW Denver 200 PM TO 800 PM Trace (50%) to 0.25" (25%) to 0.5" (10%) LOW Douglas 200 PM TO 700 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Jefferson 200 PM TO 700 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 100 PM TO 800 PM Trace (50%) to 0.25" (25%) to 0.5" (10%) LOW Douglas 100 PM TO 700 PM Trace (40%) to 0.25" (20%) to 0.5" (10%) LOW Jefferson 100 PM TO 700 PM Trace (40%) to 0.25" (20%) to 0.5" (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]