Time: 935 AM Wed May 10, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- AN ACTIVE WEATHER DAY WITH HEAVY RAINFALL LIKELY THIS AFTERNOON AND EVENING An active day weather wise with rain showers/thunderstorms likely this afternoon, evening and through the overnight. A good chance some of these storms become severe today, bringing large hail, up to 1.5”, gusty winds, 60+ mph along with heavy rainfall resulting in localized flash flooding. The best chance for strong storms will be from 1pm to midnight tonight, with rain showers/isolated thunderstorms possible through the overnight and into Thursday. Multiple rounds of strong storms will be possible this afternoon and into this evening, with storm intensities decreasing after midnight. Storm motions today will be from south to north between 10-20mph which could limit point rainfall amounts, however, additional storms formed off outflow boundaries will likely have much slower and erratic movement leading to isolated heavy rainfall. Storms will also likely contain hail, which could also help limit rainfall amounts under stronger storms today. With good upper-level support in place across the I-25 corridor, equal chances throughout the District will be possible for heavy rainfall today. The strongest upper-level support will start to move eastward after midnight tonight, bringing more widespread showers through the overnight and into daybreak Thursday. Off and on shower activity will be possible through the morning Thursday, however the threat for heavy rainfall should be minimal as cooler temperatures suppress strong storm development. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce 0.1-0.5" in 10-30 minutes. A Moderate to strong thunderstorm will produce 0.5-1.0" in 10-30 minutes. WORST CASE SCENARIO: A slow moving/stationary thunderstorm, or training of thunderstorm cells has the potential to produce up to 2.0" in under 60 minutes. A LOOK AHEAD: This active pattern remains in place through the weekend, however, today should be the most likely for a heavy rain threat. Cooler daytime temperatures tomorrow will most likely suppress strong storm development, although the threat will at least be low for a few rain showers to produce localized heavy rainfall as surface moisture remains elevated. Similar conditions in place Friday, with slightly warmer daytime temperatures will result in a slightly better chance for impactful afternoon and early evening thunderstorms. Similar conditions remain in place both Saturday and Sunday with a chance for isolated afternoon and evening rain showers/thunderstorms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Arapahoe 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Boulder 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Broomfield 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Denver 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Douglas 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Jefferson 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Foothills above 6500ft       Boulder 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Douglas 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) HIGH Jefferson 200 PM TO 1159 PM 0.1" (90%) to 0.5" (60%) to 1" (30%) 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]