Time: 245 PM Wed June 21, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S AND 2'S ISSUED FOR THE DISTRICT Message 1’s have been issued for all Counties except Douglas County in which a Message 2 (NWS Flood/Flash Flood Watch) has been issued. The Message 1’s will be valid from 3:00 PM this afternoon until 2:00 AM Thursday while the Message 2 for Douglas County is valid from 3;00 PM this afternoon until 6:00 AM Thursday but may be rescinded early should conditions warrant. Multiple ingredients are rapidly coming together for thunderstorms to develop this afternoon over the next few hours and become strong to severe into the evening. Moderate to strong thunderstorms will be very capable of producing heavy rainfall, large hail (possibly accumulating hail) and gusty winds. 1-2 rounds of strong/severe thunderstorms are expected over the course of the afternoon/evening/early overnight period. Thunderstorms will be relatively slow moving and may produce extended periods of heavy rain. Prime time for thunderstorms is from 4:00 PM this afternoon to 1:00 AM Thursday. Heavy rainfall from thunderstorms will easily produce excessive runoff roadways and may result in flash flooding within the District. Due to snow melt and recent rains many creeks and streams are already running relatively high and additional rainfall will exacerbate flows as the day progresses. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" of rain. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.6-1.8" in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 3.0" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Adams County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Denver County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY DIA 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Arapahoe County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY the City of Aurora 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Arvada 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Wheat Ridge 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Lakewood 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Douglas County 2 300 PM TO 600 AM THURSDAY 400 PM TO 100 AM THURSDAY Broomfield County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Jefferson County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY Boulder County 1 300 PM TO 200 AM THURSDAY 400 PM TO 100 AM THURSDAY County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Arapahoe 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Boulder 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Broomfield 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Denver 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Douglas 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Jefferson 300 PM TO 200 AM THU 0.2" (95%) to 0.6" (65%) to 1.8" (30%) ISSUED Foothills above 6500ft       Boulder Current TO 200 AM THU 0.2" (90%) to 0.6" (60%) to 1.8" (25%) ISSUED Douglas Current TO 200 AM THU 0.2" (90%) to 0.6" (60%) to 1.8" (25%) ISSUED Jefferson Current TO 200 AM THU 0.2" (90%) to 0.6" (60%) to 1.8" (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]