Flash Flood Prediction Program

Time: 845 AM Tue May 9, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARMER TODAY WITH ANOTHER CHANCE FOR AFTERNOON/EVE RAIN SHOWERS/ISOLATED THUNDERSTORMS Warmer today as high temperatures reach the upper 70's to nearly 80 degrees this afternoon. Another chance this afternoon and evening for a few rain showers/isolated thunderstorms, however, similar to last night, these showers will be very hit or miss across the I-25 corridor this afternoon and evening. Surface moisture will play a huge role in storm intensity today with dew points likely decreasing throughout the morning and into the afternoon. An uptick in surface moisture late this afternoon and into the early evening from the east could help initiate stronger storms later this afternoon and into this evening. There will be a low chance that these storms are able to strengthen to the point of producing heavy rainfall as dew points are projected to reach the upper 40's to low 50's this evening between 5-7pm with a good chance this elevated surface moisture sticks around through the rest of the week. The best chance for storms today will be from 5pm through midnight tonight, favoring northern portions of the District at this time. However, a gust front from a stronger storm has the potential to initiate additional storms across the District this evening. Storm intensity should diminish after midnight, with skies gradually clearing into daybreak Wednesday. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce a trace to 0.2" in 10-30 minutes. A moderate to strong thunderstorm could produce 0.2-0.5" in 10-30 minutes. WORST CASE SCENARIO: A stronger, slower moving storm formed off an out flow boundary, or training of thunderstorm cells has the potential to produce 0.5-1.5" in 30-60 minutes. A LOOK AHEAD: Upper-level flow turns southwesterly through the overnight tonight bringing a better chance for strong storm tomorrow afternoon and evening. These storms will likely produce localized heavy rainfall resulting in a better chance for some isolated flash flooding during the afternoon and early evening tomorrow. Rainfall chances will stick around through the overnight Wednesday and into Thursday with off and on rainfall chances likely throughout the day Thursday. The shower intensity Thursday will hinge on whether there is enough daytime heating. This active weather pattern continues Friday, with afternoon and evening rain showers/isolated thunderstorm chances continuing. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Arapahoe 400 PM TO 1159 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Boulder 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Broomfield 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Denver 400 PM TO 1159 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Douglas 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Douglas 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 400 PM TO 1159 PM Trace (40%) to 0.2" (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]