Flash Flood Prediction Program

Time: 1214 PM Mon May 17, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR ALL OF THE DISTRICT - Message 1's have been issued for all of the District and will be valid until 10:00pm this evening. With a moist atmosphere in place in tandem with slow storm motions thunderstorms that develop later today will be very capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. - Showers and weak thunderstorms are currently developing over portions of southern Jefferson and western Douglas Counties. Shower and thunderstorm coverage is expected to expand northward and eventually eastward as the afternoon progresses. Storm motions will be slow, at 10mph or less and thunderstorms may have a tendency to anchor or move very slowly potentially producing moderate to heavy rainfall for an extended period of time. - Best chances for thunderstorm activity looks to be from 2-8pm over the foothills and from 4-9pm over the plains. There still remains uncertainty on the potential strength of thunderstorms this afternoon as daytime heating or lack there of over the next few hours will play a major role. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4" in 10-30 minutes. Moderate to strong thunderstorms. Moderate to strong thunderstorms will have the potential to produce 0.4-1.0" in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm becomes stationary producing an extended period of heavy rainfall with up to 2.0" in 60 minutes or less. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1000 PM 400 PM TO 900 PM Jefferson County 1 Current TO 1000 PM 200 PM TO 900 PM Broomfield County 1 Current TO 1000 PM 300 PM TO 900 PM Douglas County 1 Current TO 1000 PM 200 PM TO 900 PM Adams County 1 Current TO 1000 PM 400 PM TO 900 PM Denver County 1 Current TO 1000 PM 400 PM TO 900 PM DIA 1 Current TO 1000 PM 400 PM TO 900 PM Arapahoe County 1 Current TO 1000 PM 400 PM TO 900 PM the City of Aurora 1 Current TO 1000 PM 400 PM TO 900 PM Arvada 1 Current TO 1000 PM 200 PM TO 900 PM Wheat Ridge 1 Current TO 1000 PM 200 PM TO 900 PM Lakewood 1 Current TO 1000 PM 200 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 200 PM TO 1000 PM 0.1" (90%) to 0.4" (60%) to 1.0" (20%) ISSUED Arapahoe 200 PM TO 1000 PM 0.1" (90%) to 0.4" (60%) to 1.0" (20%) ISSUED Boulder 200 PM TO 1000 PM 0.1" (90%) to 0.4" (60%) to 1.0" (20%) ISSUED Broomfield 200 PM TO 1000 PM 0.1" (90%) to 0.4" (60%) to 1.0" (20%) ISSUED Denver 200 PM TO 1000 PM 0.1" (90%) to 0.4" (60%) to 1.0" (20%) ISSUED Douglas 200 PM TO 1000 PM 0.1" (90%) to 0.4" (65%) to 1.0" (20%) ISSUED Jefferson 200 PM TO 1000 PM 0.1" (90%) to 0.4" (65%) to 1.0" (20%) ISSUED Foothills above 6500ft       Boulder 100 PM TO 1000 PM 0.1" (100%) to 0.4" (75%) to 1.0" (25%) ISSUED Douglas Current TO 1000 PM MON 0.1" (100%) to 0.4" (75%) to 1.0" (25%) ISSUED Jefferson Current TO 1000 PM MON 0.1" (100%) to 0.4" (75%) to 1.0" (25%) 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]