Flash Flood Prediction Program

Time: 457 PM Fri June 2, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONTINUE VALID/HEAVY RAINFALL THREAT RAPIDLY DECREASING/ALL CLEAR MAY BE ISSUED NEXT 1-2 HOURS Message 1’s continue valid until 8:00pm but the threat for heavy rainfall is rapidly diminishing as drier air is working its way into the District. An outflow boundary from storms outside the District may push back into the District and increase moisture and supply a trigger for new storms but the threat for this situation to play out is quite low. Isolated light rain showers will be the most likely outcome for the rest of the afternoon and evening resulting in Message 4’s (All Clear) possibly being issued over the next 1-2 hours. Rain showers and isolated to widely scattered thunderstorms are expected to increase in coverage on Saturday as the low pressure system will be to our east and “upslope” flow will be in place along the I-25 corridor. Moisture will increase and thunderstorms will be capable of producing heavy rainfall. If temperatures remain too cool precipitation may favor general rain showers versus thunderstorms. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak to moderate thunderstorms will produce a trace to 0.2" of rain. Moderate thunderstorms will have the potential to produce rainfall rates of 0.2-0.5” in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm is able to develop with the potential to produce brief heavy rainfall of 0.3-0.8" in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 800 PM Current TO 700 PM Jefferson County 1 Current TO 800 PM Current TO 700 PM Broomfield County 1 Current TO 800 PM Current TO 700 PM Douglas County 1 Current TO 800 PM Current TO 700 PM Adams County 1 Current TO 800 PM Current TO 700 PM Denver County 1 Current TO 800 PM Current TO 700 PM DIA 1 Current TO 800 PM Current TO 700 PM Arapahoe County 1 Current TO 800 PM Current TO 700 PM the City of Aurora 1 Current TO 800 PM Current TO 700 PM Arvada 1 Current TO 800 PM Current TO 700 PM Wheat Ridge 1 Current TO 800 PM Current TO 700 PM Lakewood 1 Current TO 800 PM Current TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 800 PM FRI Trace (50%) to 0.2" (20%) to 0.5" (10%) ISSUED Arapahoe Current TO 800 PM FRI Trace (50%) to 0.2" (20%) to 0.5" (10%) ISSUED Boulder Current TO 800 PM FRI Trace (50%) to 0.2" (20%) to 0.5" (10%) ISSUED Broomfield Current TO 800 PM FRI Trace (50%) to 0.2" (20%) to 0.5" (10%) ISSUED Denver Current TO 800 PM FRI Trace (50%) to 0.2" (20%) to 0.5" (10%) ISSUED Douglas Current TO 800 PM FRI Trace (65%) to 0.2" (30%) to 0.5" (10%) ISSUED Jefferson Current TO 800 PM FRI Trace (60%) to 0.2" (30%) to 0.5" (10%) ISSUED Foothills above 6500ft       Boulder Current TO 800 PM FRI Trace (75%) to 0.2" (40%) to 0.5" (10%) ISSUED Douglas Current TO 800 PM FRI Trace (75%) to 0.2" (40%) to 0.5" (10%) ISSUED Jefferson Current TO 800 PM FRI Trace (75%) to 0.2" (40%) to 0.5" (10%) 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]