Flash Flood Prediction Program

Time: 1110 AM Thu May 18, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT Message 1’s have been issued for the entire District and will be valid until 9:00pm this evening. The clouds have decreased this morning and temperatures are already reaching the low to mid 60’s and will likely warm a bit more before cloud cover increases again and storms begin to develop. Daytime heating in tandem with abundant surface moisture with dew points in the lower 50’s will result in thunderstorms developing over the next few hours and remaining possible into the evening. Best chances for thunderstorm activity through the afternoon and early evening between noon and 8pm. With all of the rain recently the ground is near saturation for many areas and thunderstorms today will have the potential to produce heavy rainfall which may result in excessive runoff and possibly flash flooding. Typical showers and thunderstorms will move from W to E at 15-20mph but stronger storms may move more slowly or become right movers and track more from the NW to SE. After 8 or 9pm the chances for thunderstorms will diminish with cooling temperatures and light rain showers are expected to continue periodically overnight into early Friday morning. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.5” of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.5” in 10-30 minutes. WORST CASE SCENARIO: A slower moving strong thunderstorm or a large thunderstorm complex may result in up to 2.0” of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 1130 AM TO 900 PM 1230 PM TO 800 PM Arvada 1 1130 AM TO 900 PM 1230 PM TO 800 PM Wheat Ridge 1 1130 AM TO 900 PM 1230 PM TO 800 PM the City of Aurora 1 1130 AM TO 900 PM 1230 PM TO 800 PM Denver County 1 1130 AM TO 900 PM 1230 PM TO 800 PM DIA 1 1130 AM TO 900 PM 1230 PM TO 800 PM Arapahoe County 1 1130 AM TO 900 PM 1230 PM TO 800 PM Adams County 1 1130 AM TO 900 PM 1230 PM TO 800 PM Boulder County 1 1130 AM TO 900 PM 1230 PM TO 800 PM Jefferson County 1 1130 AM TO 900 PM 1230 PM TO 800 PM Broomfield County 1 1130 AM TO 900 PM 1230 PM TO 800 PM Douglas County 1 1130 AM TO 900 PM 1230 PM TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 1200 PM TO 900 PM 0.1" (80%) to 0.5" (50%) to 1.5" (20%) ISSUED Arapahoe 1200 PM TO 900 PM 0.1" (85%) to 0.5" (55%) to 1.5" (25%) ISSUED Boulder 1200 PM TO 900 PM 0.1" (85%) to 0.5" (55%) to 1.5" (25%) ISSUED Broomfield 1200 PM TO 900 PM 0.1" (80%) to 0.5" (50%) to 1.5" (20%) ISSUED Denver 1200 PM TO 900 PM 0.1" (80%) to 0.5" (50%) to 1.5" (20%) ISSUED Douglas 1200 PM TO 900 PM 0.1" (90%) to 0.5" (60%) to 1.5" (30%) ISSUED Jefferson 1200 PM TO 900 PM 0.1" (85%) to 0.5" (55%) to 1.5" (25%) ISSUED Foothills above 6500ft       Boulder Current TO 900 PM THU 0.1" (90%) to 0.5" (60%) to 1.5" (30%) ISSUED Douglas Current TO 900 PM THU 0.1" (90%) to 0.5" (60%) to 1.5" (30%) ISSUED Jefferson Current TO 900 PM THU 0.1" (90%) to 0.5" (60%) to 1.5" (30%) 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]