Flash Flood Prediction Program

Time: 724 AM Fri May 20, 2022 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- UNSEASONABLY COLD WITH RAIN CHANGING TO HEAVY/WET SNOW - Powerful spring storm system will impact the District today and tonight into the day on Saturday. Currently temperatures are in the mid to upper 30's and will flat line through the day. Light to moderate rain showers or a mix of rain snow will continue through the morning with a secondary cold front moving through this afternoon lowering temperatures and changing any rain over to snow over the plains between 2-5pm. Precipitation will fall as snow in the foothills above 6,500-7,000ft through the day with snow starting to pile up over the higher terrain. - Once rain changes over to all snow later this afternoon over the plains the snow intensity is expected to increase into the evening. Snow will fall moderate to heavy at times tonight into Saturday morning. Snowfall rates over the foothills and Palmer Divide may reach the 1-3"/hr range at times under stronger snow bands. Prime time for heavy snow is from roughly 6pm this evening until 10am Saturday. Snow showers will begin to decrease in intensity later Saturday morning with conditions slowly drying out in the afternoon. - Total precipitation in the form of rain and melted snow from this morning into midday Saturday is expected to range from 1.0-1.5" of moisture with isolated higher and lower amounts. Snowfall accumulations from later today into Saturday will likely vary from 2-6" between 5,000-6,000ft and 5-10" between 6,000-7,000ft and 10-20" or more between 7,000-9,000ft. Isolated higher amounts possible each zone. STORM RAINFALL POTENTIAL AND DURATION: Light to moderate rain showers or melted snow equivalent will produce precipitation rates of 0.1-0.4" per hour. WORST CASE SCENARIO: Heavy wet snow combined with leafed out trees likely results in a "branch breaking" snowfall for many areas within the District. A LOOK AHEAD: Widespread snowfall over the District Saturday morning will be heaviest over the foothills and Palmer Divide. Snow showers will decrease as the day wears on with most of the precipitation occurring before noon. Isolated to widely scattered rain/mix/snow showers continue possible Saturday afternoon with conditions drying out in the evening. Highs on Saturday only in the 30's to lower 40's over the plains with a hard freeze likely overnight into Sunday morning. LOCATION PRIME TIME 60-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Arapahoe Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Boulder Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Broomfield Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Denver Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Douglas Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Jefferson Current TO 1000 AM SAT 0.1" (100%) to 0.2" (75%) to 0.4" (40%) NONE Foothills above 6500ft       Boulder Current TO 1000 AM SAT 0.1" (100%) to 0.2" (80%) to 0.4" (50%) NONE Douglas Current TO 1000 AM SAT 0.1" (100%) to 0.2" (80%) to 0.4" (50%) NONE Jefferson Current TO 1000 AM SAT 0.1" (100%) to 0.2" (80%) to 0.4" (50%) 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]