Flash Flood Prediction Program

Time: 855 AM Mon May 29, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- TEMPERATURES INCREASE SLIGHTLY WITH ISOLATED AFTERNOON THUNDERSTORMS Temperatures will increase slightly over the District today with afternoon highs topping out in the low to mid 80’s over the plains which is about 5 degrees above normal. The normal high for Denver today is 77 degrees. Most of the thunderstorm activity this afternoon is expected to remain to the N of the District but there will still be a slight chance for an isolated thunderstorm or two. Storms that manage to develop today will generally produce gusty winds and light rain/sprinkles, but a stronger storm could produce a brief burst of moderate rain over a small geographical area. The majority of the District will end up on the drier side today. Best chances for thunderstorm activity will be between 1pm and sunset. Upper level steering winds are from W to E at around 20mph. After 8 or 9pm dry conditions are expected for the remainder of the evening and overnight period. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and isolated weak to briefly moderate thunderstorms will produce a trace to 0.2” of rain. WORST CASE SCENARIO: Outflow from storms to the N and NE of the District push back westward increasing surface moisture resulting in a briefly strong thunderstorm with the potential to produce 0.2-0.5” of rain in 10-30 minutes. A LOOK AHEAD: A slight uptick in moisture on Tuesday and the aid of a weak upper level disturbance will lead to a few more storms with widely scattered thunderstorms in the afternoon and evening. Thunderstorms will generally produce light to brief moderate rain and possibly some hail. Temperatures will be similar to today. Moisture increases further on Wednesday and storms should be more numerous in the afternoon and evening with some storms potentially producing heavy rainfall and severe weather. Temperatures will back off a few degrees with increased cloud cover. Cooler still for Thursday and a good chance for afternoon showers and thunderstorms, some of which may contain heavy rain. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 100 PM TO 800 PM Trace (50%) to 0.1" (25%) to 0.2" (15%) NONE Arapahoe 100 PM TO 800 PM Trace (40%) to 0.1" (20%) to 0.2" (10%) NONE Boulder 100 PM TO 800 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE Broomfield 100 PM TO 800 PM Trace (40%) to 0.1" (20%) to 0.2" (10%) NONE Denver 100 PM TO 800 PM Trace (40%) to 0.1" (20%) to 0.2" (10%) NONE Douglas 100 PM TO 800 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Jefferson 100 PM TO 800 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Foothills above 6500ft       Boulder 1200 PM TO 800 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE Douglas 1200 PM TO 800 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE Jefferson 1200 PM TO 800 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]