Time: 839 AM Sat May 22, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- COOLER TODAY WITH A GOOD CHANCE FOR AFTERNOON/EVENING THUNDERSTORMS - A low-pressure system that was stalled over California will finally make its way into the region today bringing gusty southerly winds and cloudy skies with high temperatures reaching the low to mid 70's. An increase of low-level moisture from a cold front that moved in from the N/NE overnight, will bring an increased chance for afternoon rain showers and thunderstorms over the District, with a slight chance storms could turn severe favoring areas east of I-25. - Storm motions today will be brisk from the south between 10-20mph which will help limit point rainfall amounts, however storms today will have the potential for heavy rainfall, especially if a storm stalls/anchors itself and core dumps all of its moisture over and isolated area. Best chance for rain showers and thunderstorms today will be from 2-8pm with a slight chance for lingering rain showers/isolated thunderstorms through 10pm with skies starting to clear out around midnight. Storms today will also be capable of producing large hail, 1+", strong winds and frequent lightning. - Overnight temperatures will fall into the upper 40's to low 50's on the plains with low to mid 40's along the foothills. A few isolated area of patchy fog will be possible into Sunday morning favoring low lying areas. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers and thunderstorms will have the potential to produce 0.05-0.3" in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.3-0.6" in 10-30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells may result in up to 1.2" of rain in 60 minutes or less. A LOOK AHEAD: Sunday will be breezy and dry as high-pressure starts to build over the region with high temperatures reaching the mid to upper 70's. Even warmer heading into the beginning of next week with highs around 80 degrees with mostly sunny skies and dry conditions as high-pressure holds. There will be a slight chance for high-based afternoon rain showers/isolated thunderstorms Wednesday afternoon with high temperatures expected to reach the low to mid 80's. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Arapahoe 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Boulder 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Broomfield 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Denver 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Douglas 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Jefferson 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Foothills above 6500ft       Boulder 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Douglas 200 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 0.6" (25%) LOW Jefferson 200 PM TO 1000 PM Trace (75%) to 0.3" (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]