Flash Flood Prediction Program

Time: 855 AM Wed September 11, 2024 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Warm, slight uptick in moisture supporting scattered gusty showers Upper-level moisture out ahead of a potent storm system over the Pacific Northwest will be overhead today, coupled with a slight uptick in surface moisture as well. This will support one of the final days with message issuance potential for the summer thunderstorm season. Storm coverage will be isolated/scattered once daytime heating pushes temperatures in the high country past convective thresholds in the early afternoon. Mostly small, weak, and gusty showers/t-storms will meander east into the foothills and urban corridor in and around the District shortly thereafter. Outflows from dying storms will have the potential to spark other cells throughout the afternoon before storms clear out fully before sunset. Today comes with a small caveat: there is indications that a dryline is likely to form on the plains east of the District. Drylines are moisture boundaries that are ripe for strong thunderstorm development, and should it develop closer to the metro than currently anticipated, storms that form along it will have the highest chance of producing message issuance-worthy rainfall. Chances of this occurrence within the District are extremely low, but not zero, and favor the far eastern portions of the District. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce a trace-0.20" of rainfall in 10-30 minutes. Stronger thunderstorms will produce 0.20-0.50" in 10-30 minutes. WORST CASE SCENARIO: A strong/stationary thunderstorm, or training of thunderstorms along the dryline, may be capable of producing 1.00" in 60 minutes or less. A LOOK AHEAD: As summer starts to turn to fall, the Denver weather pattern will begin to calm as it does each year. Tomorrow has a chance to be DIA's final 90°F day of the year if it gets there under warm, dry southwesterly flow. Calm, dry conditions will then arrive for the weekend, with an extremely outside chance of a stray shower Sunday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Arapahoe 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Boulder 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Broomfield 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Denver 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Douglas 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 200 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 100 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Douglas 100 PM TO 700 PM Trace (30%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 100 PM TO 700 PM Trace (30%) 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]