Time: 858 AM Fri May 21, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM AND BREEZY WITH A SLIGHT CHANCE FOR DRY, HIGH-BASDED AFTERNOON THUNDERSTORMS - Dry S/SW upper-level flow will continue over the region today leading to breezy conditions throughout the day as high temperatures reach the low to mid 80's on the plains with mid to upper 70's along the foothills. A slight chance this afternoon for widely scattered high-based thunderstorms with minimal, if any, precipitation as most will evaporate before making it to the surface. - Storms will initiate along the higher terrain by midday and move out onto the plains between 1-3pm with the best chance for thunderstorm activity for the District between 2-6pm. With dewpoints in the 30's and temperatures in the 80's generally dry conditions are expected, although an isolated TR-0.1" cannot be completely ruled out if a stronger storm is able to develop favoring far eastern portions of the District. Storm chances taper off after 6pm with skies clearing into the evening. - Overnight will be breezy with lows dropping into the upper 40's to low 50's on the plains, with low to mid 40's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Dry thunderstorms will have the potential to produce a trace in 10-30 minutes. WORST CASE SCENARIO: A weak to moderate thunderstorm will have the potential to produce trace-0.1" in 10-30 minutes. A LOOK AHEAD: The low-pressure system over California will begin to creep towards Colorado this evening bringing a better chance for rain and thunderstorms Saturday afternoon with a slight chance of storms becoming severe. The largest threat at this time will be strong winds and large hail with a low chance for heavy rainfall as storm motions should be brisk between 10-20mph helping limit point rainfall totals. Sunday high-pressure returns leading to sunny and dry conditions heading into next week. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 600 PM Trace (20%) to 0.1" (10%) Arapahoe 200 PM TO 600 PM Trace (20%) to 0.1" (10%) Boulder 200 PM TO 600 PM Trace (20%) to 0.1" (5%) Broomfield 200 PM TO 600 PM Trace (20%) to 0.1" (5%) Denver 200 PM TO 600 PM Trace (20%) to 0.1" (5%) Douglas 200 PM TO 600 PM Trace (20%) to 0.1" (5%) Jefferson 200 PM TO 600 PM Trace (20%) to 0.1" (5%) Foothills above 6500ft       Boulder 100 PM TO 500 PM Trace (20%) to 0.1" (5%) Douglas 100 PM TO 500 PM Trace (20%) to 0.1" (5%) Jefferson 100 PM TO 500 PM Trace (20%) to 0.1" (5%) MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]