Time: 1017 AM Sun August 25, 2024 Forecaster: Tim Tonge ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Late afternoon/evening isolated showers and thunderstorms persisting overnight Satellite imagery analysis this morning shows a well-defined pocket of dry air over western Colorado, embedded within the greater monsoonal setup. This dry air will traverse the state this morning until it reaches the District, hindering storm development throughout the majority of the afternoon. By late afternoon, synoptic-scale lift will arrive as a jet streak intensifies over the northern High Plains, placing Colorado under its right entrance region. The forcing from this jet streak will spark isolated showers and thunderstorms in the high country south and west of the District in the late afternoon, which will then travel north/northeast into the foothills and plains of the District shortly thereafter. Similar to yesterday, storms will be more likely to cause gusty outflows than heavy rainfall due to warm temperatures, afternoon dewpoints in the mid/upper 30s, and relatively fast storm motions. The pocket of dry air will have passed by late evening, and available water will increase overnight. Those factors, assisted by the jet streak, will lead to a chance that showers and thunderstorms linger overnight and into Monday morning, with higher chances of rainfall overnight than this afternoon/evening. Overall, the threat of heavy rainfall is extremely low today due to a lack of surface moisture, but the potential for moisture to return this evening will drive a LOW potential for message issuance today rather than NONE. STORM RAINFALL POTENTIAL AND DURATION: Typical showers and thunderstorms will produce 0.05"-0.25" of rainfall in 10-30 minutes. Stronger thunderstorms will produce 0.25"-0.50" in 10-30 minutes. WORST CASE SCENARIO: A strong/stationary thunderstorm, or training of thunderstorms, could be capable of producing 1.25" of rainfall total in 60 minutes or less. A LOOK AHEAD: Once any morning showers have cleared, tomorrow will be rinse and repeat with late afternoon storms arriving in isolated fashion, though a slight uptick in moisture will leave tomorrow's storms a bit more rainfall-friendly. Almost entirely dry Tuesday/Wednesday, then a cold front overnight Wednesday will drop temps a few degrees and bring back storm chances heading into the weekend. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Arapahoe 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Boulder 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Broomfield 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Denver 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Douglas 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Jefferson 400 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 300 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Douglas 300 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) to 0.5" (10%) LOW Jefferson 300 PM TO 100 AM MON 0.05" (40%) to 0.25" (30%) 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]