Time: 902 AM Fri July 21, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SUNNY AND WARM WITH A SLIGHT CHANCE FOR LATE AFTERNOON SHOWERS/THUNDERSTORMS Strong northwesterly flow aloft has cleared out the disturbance that moved through the region yesterday. Mild and sunny conditions are expected throughout most of the day today with high temperatures reaching the low to mid 80’s this afternoon. A weak disturbance will move through northeastern Colorado late this afternoon and into the early evening bringing a slight chance of showers and thunderstorms into the District. The best chance for storms will be between 4-8pm. Storm motions will be from the NW to SE between 20-30mph which should help limit point rainfall amounts. However, due to elevated surface dew points, currently in the upper 50’s to around 60, and adequate daytime heating, there will be a LOW chance for Message 1’s to be issued. Mainly for the threat of a slower moving storm formed along an outflow boundary. Skies will quickly clear out behind this disturbance with no additional storms likely after sunset. Overnight lows will drop into the low 60s. Tomorrow will be even warmer with highs around 90. STORM RAINFALL POTENTIAL AND DURATION: Typical showers or a weak thunderstorm will produce a TR-0.25” total in 10-30 minutes. A moderate thunderstorm will produce 0.25-0.50” total in 10-30 minutes. WORST CASE SCENARIO: A moderate to strong slow-moving thunderstorm has the potential to produce up to 1.0” in under 60 minutes. A LOOK AHEAD: Northwesterly flow aloft continues tomorrow leading to even drier conditions with mostly sunny skies. Not much change on Sunday with sunny skies as high temperatures reach the upper 90’s. Around 100 degrees Monday with a slight chance of high based showers and possibly a weak thunderstorm or two. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 400 PM TO 800 PM Trace (40%) to 0.25" (20%) to 0.5" (15%) LOW Arapahoe 400 PM TO 800 PM Trace (40%) to 0.25" (20%) to 0.5" (15%) LOW Boulder 400 PM TO 800 PM Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Broomfield 400 PM TO 800 PM Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Denver 400 PM TO 800 PM Trace (30%) to 0.25" (15%) to 0.5" (10%) LOW Douglas 400 PM TO 800 PM Trace (25%) to 0.25" (15%) to 0.5" (10%) LOW Jefferson 400 PM TO 800 PM Trace (25%) to 0.25" (15%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 400 PM TO 800 PM Trace (20%) to 0.25" (15%) to 0.5" (10%) LOW Douglas 400 PM TO 800 PM Trace (20%) to 0.25" (15%) to 0.5" (10%) LOW Jefferson 400 PM TO 800 PM Trace (20%) to 0.25" (15%) to 0.5" (10%) 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]