Flash Flood Prediction Program

Time: 858 AM Sat August 5, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- A CHANCE FOR SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON AND INTO THIS EVENING Mild and dry currently, a change is in the air today as a cold front is poised to move through the region this afternoon. This cold front should have no issues getting a few showers and isolated thunderstorms going this afternoon and possibly into the evening hours. Slightly less moisture at the surface currently should increase behind the cold front bringing dew points back into the upper 50’s to around 60. This will result in a MODERATE chance for Message 1’s as the potential for a quick 0.25-0.75” in 10-30 minutes will be possible today. Initial storm development will be along the higher terrain by midday with showers/isolated thunderstorms moving into the District between 2-8pm. Storm motions will continue to be brisk from W to E between 15-25mph, effectively limiting any point rainfall amounts. However, a stronger storm will have the potential to produce outflow boundaries which additional storm develop could stall out along, bringing the best chance for moderate to brief heavy rainfall, favoring eastern portions of the District at this time. Skies will stay partly through the overnight with lows in the mid to upper 50’s on the plains with low 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.75” total in 10-30 minutes. WORST CASE SCENARIO: A stronger, stalled out thunderstorm formed along an outflow boundary is able to develop, will have the potential to produce up to 1.25” total, in under 60 minutes. A LOOK AHEAD: Cooler temperatures behind this cold front will dictate the strength of storms tomorrow as highs are expected to stay in the 70s. An uptick in overall moisture will likely bring a chance for moderate to brief heavy rainfall throughout most of the afternoon with chances picking up into the evening. Storm chances remain Monday, with another decent chance for afternoon/eve showers/isolated thunderstorms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Arapahoe 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Boulder 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Broomfield 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Denver 200 PM TO 900 PM 0.05" (65%) to 0.25" (35%) to 0.75" (20%) MOD Douglas 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Jefferson 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Foothills above 6500ft       Douglas 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Jefferson 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Boulder 100 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]