Time: 939 AM Mon July 22, 2024 Forecaster: Tim Tonge ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- Warming today with isolated showers/thunderstorms this afternoon and early evening The active pattern has mostly passed for the time being, and chances of measurable rainfall decrease today and for the most of the work week. The southwestern US ridge has begun its slow return to Colorado, and northerly flow has delivered a drier airmass from the Great Basin to the District today. Morning dewpoints in the low 50s are forecasted to mix down to the low 40s by the time isolated seasonal convection starts over the high country west of the District. Storms that reach the foothills and plains in and around the District will have 0.7”-0.8” inches of precipitable water (PWAT) to work with, and will be capable of brief thunderstorm downpours of 0.25”-0.50” in 10-30 minutes, moving from NNW to SSE at 10-15mph. Forecast model guidance suggests that storms in the District today are unlikely, but enough residual moisture and energy remains in the atmosphere that the District will have a LOW probability of message issuance during a window between 1pm and 8pm. STORM RAINFALL POTENTIAL AND DURATION: Typical showers and thunderstorms will produce 0.25"-0.50" in 10-30 minutes. Stronger storms at higher elevations may produce 0.75" in 10-30 minutes. WORST CASE SCENARIO: A slow-moving or stationary shower or thunderstorm may be capable of producing 1.00" in 30 minutes or less. A LOOK AHEAD: The warming and drying trend continues tomorrow, and the probability of message issuance will likely be NONE. There is a small uptick in moisture as temperatures continue to warm Wednesday; likely dry Thursday before moisture returns this weekend. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Arapahoe 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Boulder 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Broomfield 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Denver 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Douglas 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Jefferson 100 PM TO 800 PM Trace (30%) to 0.3" (20%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder 100 PM TO 800 PM 0.1" (30%) to 0.3" (20%) to 0.8" (10%) LOW Douglas 100 PM TO 800 PM 0.1" (30%) to 0.3" (20%) to 0.8" (10%) LOW Jefferson 100 PM TO 800 PM 0.1" (30%) to 0.3" (20%) to 0.8" (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]