Flash Flood Prediction Program

Time: 904 AM Sun August 7, 2022 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM TODAY WITH A GOOD CHANCE FOR HEAVY RAINFALL THIS AFTERNOON AND EVENING - Not much change in the overall pattern from yesterday with SW upper-level flow continuing to dominate over the region today as dew points remain elevated in the upper 50's to low 60's this morning. Clouds have moved eastward bringing mostly sunny skies early which will help enhance daytime heating with highs expected in the mid to upper 80's this afternoon. Combined with adequate surface moisture, the chance for heavy rainfall will be HIGH as the National Weather Service has issued a Flood Watch in effect from 2pm this afternoon until midnight tonight. - This Flood Watch will coincide with the issuance of Message 2's from 2pm this afternoon effective until midnight tonight. Initial storm development is expected to form along the higher terrain between noon and 2pm with storms moving onto the foothills between 1-3pm. Storms will then move into the District between 2-4pm with multiple rounds of storms likely through the evening before rainfall chances taper off around midnight. Storm motions will be slow today as steering winds remain fairly week with generally W/SW to E/NE storm movement between 3-8mph, however, strong storms have the potential to form along outflow boundaries and anchor in place for an extended period of time resulting in an increased chance for heavy rainfall. Heavy rainfall rates today will be between 1-3" per hour, although the likelihood of a storm lasting over one hour at a certain point remains very low at this time. - Storms that form today will have a chance to become severe, favoring areas along and east of I-25. These storms may contain gusty winds 60+mph, large hail up to 1.5" and frequent cloud-to-ground lightning. After sunset, the intensity of storms should decrease with skies gradually clearing through the overnight and into Monday morning. Overnight lows will drop into the upper 50's to low 60's with mild conditions expected through daybreak tomorrow. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/thunderstorms will produce 0.2-0.6" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.6-1.6" in 10-30 minutes. WORST CASE SCENARIO: A strong anchored thunderstorm or a slower moving large thunderstorm may result in rainfall rates up to 3.2" in 45-60 minutes. A LOOK AHEAD: Slightly cooler across the District tomorrow with drier air moving in from the NW will help limit storm activity for the afternoon and evening. A chance will remain for a few rain showers/isolated thunderstorms, with likely a low if not moderate chance for heavy rainfall, especially if we get saturated at the surface today. Conditions start to dry out Tuesday with a slight chance for a scattered rain showers, mainly along the foothills and Palmer Divide. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (30%) HIGH Arapahoe 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (30%) HIGH Boulder 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (20%) HIGH Broomfield 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (25%) HIGH Denver 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (25%) HIGH Douglas 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (25%) HIGH Jefferson 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (20%) HIGH Foothills above 6500ft       Boulder 200 PM TO 1159 PM 0.2" (90%) to 0.6" (50%) to 1.6" (25%) HIGH Douglas 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (25%) HIGH Jefferson 200 PM TO 1159 PM 0.2" (80%) to 0.6" (40%) to 1.6" (20%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]