Time: 1049 PM Thu May 11, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2'S WILL BE EXTENDED UNTIL NOON FRIDAY/RAIN TO CONTINUE OVERNIGHT WITH EXCESSIVE RUNOFF AND LOCALIZED FLOODING Message 2’s (NWS Flood Watch/Flash Flood Watch) will be extended until noon Friday. 2.0-5.0” of rain has fallen across the District over the past 1-2 days (isolated higher and lower amounts) and another 1.0-3.0” of rain or more is expected this evening and overnight. Non-thunderstorm rain showers on top of saturated ground is resulting in even light to moderate rainfall resulting in excessive runoff that is producing low end nuisance to moderate flood conditions across the District. Rain showers will continue to be persistent overnight with typical rainfall rates of 0.1-0.3” in 60 minutes and upwards of 0.3-0.9” in 60 minutes with isolated higher amounts. Although the intensity of the rain is not heavy compared to thunderstorms the overall amount of rain is producing flooding of local creeks and streams. Additional rainfall will easily runoff and may exacerbate flooding of watercourses further and result in more severe flooding as this unusual rain event continues. Any infrastructure failures may exacerbate flood conditions further and flash flooding may occur unexpectedly. As the low pressure system spinning over E/SE Colorado slowly moves eastward tomorrow rain showers are expected to decrease into the afternoon and conditions will improve but we are 10-16 hours away from significant improvement and conditions may deteriorate further before they improve tomorrow. STORM RAINFALL POTENTIAL AND DURATION: Light rain showers will produce rainfall rates of 0.1-0.3" in 60 minutes. Moderate to heavy non-thunderstorm rain showers will produce rainfall rates of 0.3-0.9" in 60 minutes. WORST CASE SCENARIO: Very heavy rain showers or a weak to moderate thunderstorm has the potential to produce rainfall amounts of 0.5-1.5" in 30-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Jefferson County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Broomfield County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Douglas County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Adams County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Denver County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY DIA 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Arapahoe County 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY the City of Aurora 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Arvada 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Wheat Ridge 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY Lakewood 2 Current TO 1159 AM FRIDAY Current TO 1000 AM FRIDAY County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 60-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1159 AM FRI 0.1" (100%) to 0.3" (75%) to 0.9" (25%) ISSUED Arapahoe Current TO 1159 AM FRI 0.1" (100%) to 0.3" (75%) to 0.9" (25%) ISSUED Boulder Current TO 1159 AM FRI 0.1" (100%) to 0.3" (70%) to 0.9" (15%) ISSUED Broomfield Current TO 1159 AM FRI 0.1" (100%) to 0.3" (70%) to 0.9" (15%) ISSUED Denver Current TO 1159 AM FRI 0.1" (100%) to 0.3" (75%) to 0.9" (25%) ISSUED Douglas Current TO 1159 AM FRI 0.1" (100%) to 0.3" (75%) to 0.9" (25%) ISSUED Jefferson Current TO 1159 AM FRI 0.1" (100%) to 0.3" (70%) to 0.9" (15%) ISSUED Foothills above 6500ft       Boulder Current TO 1159 AM FRI 0.1" (100%) to 0.3" (70%) to 0.9" (15%) ISSUED Douglas Current TO 1159 AM FRI 0.1" (100%) to 0.3" (75%) to 0.9" (25%) ISSUED Jefferson Current TO 1159 AM FRI 0.1" (100%) to 0.3" (70%) to 0.9" (15%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]