Flash Flood Prediction Program

Time: 828 AM Sat August 20, 2022 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH ANOTHER CHANCE FOR SHOWERS/THUNDERSTORMS THIS AFTERNOON AND EVENING - Northwesterly upper-level flow aloft will turn westerly as a strong disturbance moves just south of Colorado during the day today. A cold front that passed through last night will limit daytime temperatures today which could help decrease the rainfall severity throughout the day and evening. - Today's high temperatures will almost touch 80 degrees this afternoon before clouds start to increase as storms initiate along the higher terrain around midday. Showers and thunderstorms will likely move into the District between 2-4pm with rain/thunderstorms chances through 10pm-midnight, with a slight chance for a few scattered overnight rain showers and possibly an isolated thunderstorm or two. However, the best chance for heavy rainfall will be through 10pm as showers are expected to taper off in intensity into the late evening hours. - Storm motions today will also increase chances for brief heavy rain as slow motions from west to east up to 5mph will result in a high likelihood of some stationary storm movements this afternoon and evening. That being said, the largest threat will be a quick 0.5" in 10-15 minutes as most storms pulse up and down fairly quickly today. Although a stronger anchored storm, or training of thunderstorm cells could produce extended periods of moderate to heavy rainfall this afternoon and early evening. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers will only produce a trace to 0.2" of rainfall in 10-30 minutes. A moderate rain shower/isolated thunderstorm could produce 0.2- 0.6" in 10-30 minutes. WORST CASE SCENARIO: A strong anchored rain shower/thunderstorm, or training of rain showers/thunderstorms have the potential to produce 0.6-1.8" in 45-60 minutes. A LOOK AHEAD: This active pattern holds into Sunday with another chance for off and on rain showers/thunderstorms during the day with some of these likely to produce brief heavy rainfall in the afternoon and early evening. Conditions start to dry out slightly Monday and Tuesday, however a chance will remain for afternoon/evening rain showers/isolated thunderstorms, with a minimal chance for heavy rain at this time. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1000 PM Trace (60%) to 0.2" (30%) to 0.6" (15%) LOW Arapahoe 200 PM TO 1000 PM Trace (60%) to 0.2" (30%) to 0.6" (15%) LOW Boulder 200 PM TO 1000 PM Trace (70%) to 0.2" (40%) to 0.6" (20%) LOW Broomfield 200 PM TO 1000 PM Trace (60%) to 0.2" (30%) to 0.6" (15%) LOW Denver 200 PM TO 1000 PM Trace (60%) to 0.2" (30%) to 0.6" (15%) LOW Douglas 200 PM TO 1000 PM Trace (70%) to 0.2" (40%) to 0.6" (20%) LOW Jefferson 200 PM TO 1000 PM Trace (70%) to 0.2" (40%) to 0.6" (20%) LOW Foothills above 6500ft       Boulder 200 PM TO 1000 PM Trace (80%) to 0.2" (50%) to 0.6" (25%) LOW Douglas 200 PM TO 1000 PM Trace (80%) to 0.2" (50%) to 0.6" (25%) LOW Jefferson 200 PM TO 1000 PM Trace (80%) to 0.2" (50%) to 0.6" (25%) 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]