Flash Flood Prediction Program

Time: 901 AM Tue August 8, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER CHANCE FOR SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON AND LATE INTO THIS EVENING Westerly upper-level flow continues to dominate over the region today. Mild and dry currently, storms will likely initiate along the higher terrain by or just after midday. These storms will move eastward and onto the plains during the afternoon, between 2-4pm, likely increasing in strength east of I-25 as they move out of the District. Storms today will continue to move from west to east between 20-30mph, which will help limit point rainfall amounts. However, with a low chance of severe weather today, will result in at least a LOW chance for Message 1’s to be issued this afternoon and evening as there will be a threat for brief isolated heavy rainfall. Two or three rounds of storms will be possible today, lasting into the early overnight as upper-level winds increase over the region through the evening. A slight chance for severe weather today, especially areas east of I-25 for gusty winds 60mph and hail up to 1”. Due to storm motions, the largest threat for heavy rainfall today will be a quick 0.5” in 10-15 minutes, with a chance for isolated higher amounts if storms anchor along outflow boundaries for an extended period. Skies will stay partly cloudy through the overnight with lows in the mid to upper 50’s to low 60’s on the plains with low to mid 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 0.25-0.50” 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 1.00” total, in under 60 minutes. A LOOK AHEAD: High-pressure starts to build tomorrow leading to a slight dry stretch over the Denver metro Wednesday and likely Thursday as high temperatures flirt with the 90 degrees. A better chance for showers/isolated thunderstorms Friday and Saturday, however, the threat for any heavy rainfall remains minimal, at best. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1159 PM 0.05" (50%) to 0.25" (25%) to 0.5" (15%) LOW Arapahoe 200 PM TO 1159 PM 0.05" (50%) to 0.25" (25%) to 0.5" (15%) LOW Boulder 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Broomfield 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Denver 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Douglas 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Jefferson 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Douglas 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) to 0.5" (10%) LOW Jefferson 200 PM TO 1159 PM 0.05" (40%) to 0.25" (20%) 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]