Flash Flood Prediction Program

Time: 926 AM Fri May 19, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- CLOUDY/HAZY/COOL AND SHOWERY WITH ANY THUNDERSTORMS LIKELY LIMITED TO THE FOOTHILLS AND PALMER DIVIDE Conditions will be cloudy to mostly cloudy and cool today with hazy conditions due to smoke from wildfires in Canada being drawn into NE Colorado by northerly winds. Temperatures will reach the lower 60’s for highs over the plains with 50’s in the Front Range foothills. Normal high for Denver today is 73 degrees. Areas of mist and light rain showers will be possible through the morning favoring areas closer to the foothills (W of I-25) with relatively light amounts. Thunderstorm chances this afternoon will hinge upon if we see a break in the clouds and get a little more warmth and thunderstorms are not expected today over the plains but cannot be completely ruled out this afternoon should an extended break in the clouds develop. Better chances for an isolated weak to moderate thunderstorm will reside over the foothills and Palmer Divide. The outside threat for a thunderstorm will result in a low Message potential today as any thunderstorms will be capable of producing briefly heavy rain. Isolated to widely scattered rain showers will be the most likely outcome through the afternoon as cloud cover is expected to be persistent. Rain showers will produce minor rainfall amounts through the day with most areas under 0.5” of total accumulation over a 10 to 12-hour period. Conditions dry out this evening by 8 or 9pm with clouds dissipating overnight. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce rainfall amounts of TR-0.2” in 30-60 minutes. Weak thunderstorms will have the potential to produce rainfall rates of 0.2-0.5” in 10-30 minutes. WORST CASE SCENARIO: More sunshine and daytime heating occurs with moderate to strong thunderstorms developing with the potential to produce heavy rainfall of 0.3-0.8” in 10-30 minutes and up to 1.2” in 45-60 minutes. A LOOK AHEAD: We will wake up to mostly sunny skies on Saturday and with more sunshine temperatures will warm into the 70’s over the plains with 60’s in the foothills. Showers and thunderstorms will develop over the higher terrain to the W of the District on Saturday afternoon but upper level steering winds are light and the majority of the activity will remain over the mountains and foothills with low chance for any thunderstorm activity to reach the I-25 corridor. Should a thunderstorm develop over the plains, slow storm motions and residual moisture will result in storms having the potential to produce heavy rainfall. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 900 PM FRI Trace (95%) to 0.2" (50%) to 0.5" (10%) LOW Arapahoe Current TO 900 PM FRI Trace (95%) to 0.2" (50%) to 0.5" (10%) LOW Boulder Current TO 900 PM FRI Trace (100%) to 0.2" (60%) to 0.5" (10%) LOW Broomfield Current TO 900 PM FRI Trace (95%) to 0.2" (50%) to 0.5" (10%) LOW Denver Current TO 900 PM FRI Trace (95%) to 0.2" (50%) to 0.5" (10%) LOW Douglas Current TO 900 PM FRI Trace (100%) to 0.2" (60%) to 0.5" (10%) LOW Jefferson Current TO 900 PM FRI Trace (100%) to 0.2" (60%) to 0.5" (10%) LOW Foothills above 6500ft       Boulder Current TO 900 PM FRI Trace (100%) to 0.2" (75%) to 0.5" (25%) LOW Douglas Current TO 900 PM FRI Trace (100%) to 0.2" (75%) to 0.5" (25%) LOW Jefferson Current TO 900 PM FRI Trace (100%) to 0.2" (75%) to 0.5" (25%) 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]