Flash Flood Prediction Program

Time: 903 AM Tue May 11, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER COOL DAY WITH RAIN SHOWERS LIKELY THIS AFTERNOON AND EARLY EVENING - Cloudy and cool again with some widely scattered showers this morning. High temperatures today will only reach the low 40's on the plains with mid to upper 30's in and around the foothills resulting in snow falling above 7.5k and a mix of rain and snow between 6.5-7.5k with rain below 6.5k through the afternoon and early evening before precipitation chances taper off between 7-8pm. - A lull in shower activity at this time, with rain shower chances picking up by midday. With the cool temperatures precipitation is expected to favor light to moderate non-thunderstorm rain. If a thunderstorm were to develop it would likely be early on today and with low freezing levels small hail or graupel/snow pellets would be the primary culprit. Rainfall rates this afternoon expected to be in the TR-0.2"/hr range, with 0.5"/hr peak intensities possible. - A very brief timeframe this evening where we could see a rain/mix, from roughly 6pm to 8pm with up to a trace of accumulations possible on grass. By 8pm skies will gradually start to clear with overnight lows at or just above freezing through the overnight and into Wednesday morning. Lingering moisture could produce foggy conditions for Wednesday morning's commute with skies clearing through the morning. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce precipitation rates of TR-0.2" per hour. Moderate to heavy non-thunderstorm rain may result in up to 0.5" per hour rainfall rate. WORST CASE SCENARIO: A weak thunderstorm is able to develop and may result in and isolated 0.2-0.6" of rain in 10-30 minutes. A LOOK AHEAD: Warmer Wednesday as high temperatures jump back into the 60's with some residual surface moisture left over could result in some scattered rain showers/thunderstorms during the afternoon. Drier conditions move in as high-pressure settles over the region into the later part of the week as high temperatures reach the low to mid 70's Thursday and Friday with dry conditions likely, although a few high-based storms cannot be completely ruled out for Friday afternoon/early evening. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Arapahoe 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Boulder 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Broomfield 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Denver 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Douglas 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Jefferson 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Foothills above 6500ft       Boulder 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Douglas 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) NONE Jefferson 1200 PM TO 800 PM Trace (80%) to 0.2" (75%) to 0.5" (5%) 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]