Time: 934 AM Sun September 15, 2024 Forecaster: Aaron O ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Isolated Showers this Afternoon with Mostly Sunny Skies Today will be on the warmer side, with afternoon temperatures in the upper 80s. Dewpoints are in the upper 30s to upper 40s across The District and are expected to decrease throughout the day. Due to downsloping winds, the afternoon dewpoints will likley mix out into the low 30s, possibly as low as the upper 20s, which should limit rainfall amounts from an approaching shortwave this afternoon/evening. Precipitable water values are expected to be between 0.50” and 0.65”, which could potentially bring some moderate rainfall amounts, but due to lower surface dewpoints and 15-20 mph SSW to NNE storm motions, rainfall should remain below Message level amounts. Any convection will weaken after sunset and any shower activity will dissipate by 9 pm, with skies mostly clearing out overnight. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce rainfall rates of up to 0.10” total in 15-30 minutes. WORST CASE SCENARIO: A moderate to strong thunderstorm has the potential to produce up to 0.30” total rainfall 15-30 minutes. A LOOK AHEAD: Tomorrow will be slightly cooler and have a much lesser chance of convection due to a strong zonal flow creating downsloping across The District. Most convection will remain well west of The District, around the Continental Divide and possibly the higher elevations. An isolated shower or two could make it off the Continental Divide and into The District but will be very limited in point rainfall amounts as dewpoints and PWAT values will remain low. Tuesday will have a cold frontal passage, inducing one wave of convection. This wave will be heavily impacted by downsloping, limiting point rainfall amounts to be minimal. Wednesday through Friday will remain dry due to a high pressure system across Colorado. This weekend may see the first real winter-like upslope event post cold frontal passage. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Arapahoe 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Boulder 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Broomfield 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Denver 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Douglas 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Jefferson 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Foothills above 6500ft       Boulder 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Douglas 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (5%) NONE Jefferson 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.3" (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]