Time: 900 AM Mon May 20, 2024 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Cooler today with a chance for afternoon showers and isolated thunderstorms Slightly cooler today as high temperatures reach the mid to upper 70s this afternoon. Clouds will increase by midday as a few showers and isolated thunderstorms initiate along the higher terrain foothills and Palmer Divide. Dew points today will remain in the upper 30s to around 40 degrees, which should help limit storm strength this afternoon and evening. Although, good southwesterly upper-level support could result in some stronger storm development, favoring areas east of I-25 at this time. Storm motions will also be brisk, between 10-20mph from W/SW to E/NE which should also help limit any point rainfall amounts today. The best chance for storms will be between 1pm-9pm. A LOW chance for moderate to brief heavy rainfall today, mainly due to a storm forming off and outflow boundary, stalling over a certain area and producing a quick 0.50” in 10-20 minutes, rather than any long-lasting heavy rainfall. A chance for a few waves of showers well into the evening and overnight, with the best chance for impactful rainfall during the afternoon and early evening. Overnight lows will drop into the low 50s on the plains with low to mid 40s along the foothills. A cold front moves through overnight and into Tuesday resulting in a chance for a few lingering off and on light showers into the morning hours Tuesday. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce a trace to 0.25” total in 10-30 minutes. A weak to moderate shower/thunderstorm will produce 0.25”-0.50” total in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm, or training of thunderstorm cells will have the potential to produce 0.50” to 0.80” total in up to 60 minutes. A LOOK AHEAD: A continued chance for showers overnight and into Tuesday. Tuesday will remain cool with highs in the low 60s and will likely limit rainfall potential with off and on showers likely throughout most of the day and into the evening. A slight chance for a few thunderstorms in the afternoon as daytime temperatures hit the peak heating for the day. Any thunderstorm activity will likely bring a chance for moderate to brief heavy rainfall tomorrow, likely keeping a LOW chance for Messages tomorrow as well. Conditions start to dry out late Tuesday evening, overnight and into Wednesday with only a slight chance for the typical afternoon spring showers and isolated thunderstorms Wednesday afternoon. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM Trace (90%) to 0.25" (60%) to 0.5" (30%) LOW Arapahoe 200 PM TO 900 PM Trace (90%) to 0.25" (60%) to 0.5" (30%) LOW Boulder 200 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Broomfield 200 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Denver 200 PM TO 900 PM Trace (90%) to 0.25" (60%) to 0.5" (30%) LOW Douglas 200 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Jefferson 200 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Foothills above 6500ft       Boulder 100 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Douglas 100 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) LOW Jefferson 100 PM TO 900 PM Trace (80%) to 0.25" (40%) to 0.5" (20%) 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]