Time: 1013 AM Sun August 18, 2024 Forecaster: Tim Tonge ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Warm, scattered afternoon/evening showers/thunderstorms The monsoonal moisture transport setup is back in place today and tomorrow. Precipitable water (PWAT) values around 0.85" are typical of mid August, and under temperatures in the low 90s combined with dewpoints in the low/mid 40s, most showers and thunderstorms today will produce more gusty outflow concerns than heavy rainfall. At higher elevations within the foothills and on the Palmer Divide where surface temperatures are cooler, more efficient rainfall is possible, lending to a LOW probability of message issuance associated with a round of storms beginning in the mid/late afternoon. With the threat of strong outflow gusts, boundary-driven initiation is possible in and around the District through the evening before storms fully clear out overnight. Because of the possibility of this type of storm initiation, rainfall chances will linger beyond sunset. STORM RAINFALL POTENTIAL AND DURATION: Typical showers and thunderstorms will produce 0.05"-0.25" of rainfall in 10-30 minutes. Stronger storms, likely at higher elevations, will produce up to 0.50" in 10-30 minutes. WORST CASE SCENARIO: A strong/stationary thunderstorm, or training of thunderstorms, could be capable of producing up to 1.50" in 60 minutes or less. A LOOK AHEAD: Moisture chances for the work week will peak tomorrow as PWAT values approach 150% of normal under the monsoon. The upper-level setup shifts slightly Tuesday and Wednesday, cutting off the incoming stream of available moisture briefly before rainfall chances increase again going into the weekend. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Arapahoe 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Boulder 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Broomfield 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Denver 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Douglas 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Jefferson 300 PM TO 1000 PM 0.05" (30%) to 0.1" (20%) to 0.25" (10%) LOW Foothills above 6500ft       Boulder 200 PM TO 900 PM 0.1" (50%) to 0.25" (30%) to 0.25" (10%) LOW Douglas 200 PM TO 900 PM 0.1" (50%) to 0.25" (30%) to 0.25" (10%) LOW Jefferson 200 PM TO 900 PM 0.1" (50%) to 0.25" (30%) to 0.25" (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]