Time: 146 AM Thu May 11, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 2:00 AM/NON-THUNDERSTORM RAIN TO CONTINUE OVERNIGHT Message 1’s will be allowed to expire at 2:00 AM as the threat for heavy rainfall from potential thunderstorms has diminished. Scattered to widespread light to moderate rain showers will continue likely overnight and produce minor runoff but flash flooding from heavy rainfall is not expected. Creeks and streams will be running high area wide due to rain this evening and overnight with additional rain showers into tomorrow morning. Rainfall amounts through 1:30 AM in the District typically ranged from 0.75-1.50” with isolated higher amounts under thunderstorms and another 0.25-0.75” of rain is possible through mid-morning Thursday with additional rain through the afternoon and evening. Rain showers will continue to impact the District on Thursday as a low pressure system churns to the S/SE of Colorado with thunderstorms possible once again from late morning into the early evening capable of producing heavy rain. The strength/severity of the storms is expected to be weaker than Wednesday. Due to all the rain recently, the ground is becoming saturated and it may not take as much rain during the day Thursday to produce excessive runoff and Message 1’s are expected to be issued once again. STORM RAINFALL POTENTIAL AND DURATION: Non-thunderstorm rain showers will produce will produce rainfall rates of 0.1-0.4" in 30-60 minutes. WORST CASE SCENARIO: Weak to moderate thunderstorms are able to develop with the potential for heavy rainfall of 0.3-0.8" in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 200 AM Current TO 200 AM Jefferson County 1 Current TO 200 AM Current TO 200 AM Broomfield County 1 Current TO 200 AM Current TO 200 AM Douglas County 1 Current TO 200 AM Current TO 200 AM Adams County 1 Current TO 200 AM Current TO 200 AM Denver County 1 Current TO 200 AM Current TO 200 AM DIA 1 Current TO 200 AM Current TO 200 AM Arapahoe County 1 Current TO 200 AM Current TO 200 AM the City of Aurora 1 Current TO 200 AM Current TO 200 AM Arvada 1 Current TO 200 AM Current TO 200 AM Wheat Ridge 1 Current TO 200 AM Current TO 200 AM Lakewood 1 Current TO 200 AM Current TO 200 AM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 60-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Arapahoe Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Boulder Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Broomfield Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Denver Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Douglas Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Jefferson Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Foothills above 6500ft       Boulder Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Douglas Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (25%) LOW Jefferson Current TO 1000 AM THU Trace (100%) to 0.2" (75%) to 0.4" (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]