Flash Flood Prediction Program

Time: 723 PM Fri June 2, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 8:00 PM/RAIN SHOWERS EXPECTED TO BUILD IN OVERNIGHT AND A THUNDERSTORM CANNOT BE RULED OUT Message 1’s will be allowed to expire as the threat for heavy rainfall has ended at least temporarily. Conditions are expected to be generally dry this evening but if an outflow boundary from storms to the E or S of the District pushes through new storm development may occur and Message 1’s could be re-issued. Rain showers are expected to build in overnight after midnight and likely linger into Saturday morning with possibly an isolated thunderstorm. Precipitation overnight will remain light as long as thunderstorms do not develop. Rain showers and isolated to widely scattered thunderstorms are expected to increase in coverage Saturday morning 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 that may lead to excessive runoff and possibly flash flooding. If temperatures remain too cool precipitation may favor general light to moderate rain showers versus thunderstorms. Either way a wet day is in store for Saturday and Message 1’s will likely be issued by noon or before. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.3” of rain in 10-30 minutes. WORST CASE SCENARIO: Should a moderate to strong thunderstorm develop rainfall rates of 0.3-0.8” in 10-30 minutes is possible and up to 1.5” in 45-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 800 PM Current TO 730 PM Jefferson County 1 Current TO 800 PM Current TO 730 PM Broomfield County 1 Current TO 800 PM Current TO 730 PM Douglas County 1 Current TO 800 PM Current TO 730 PM Adams County 1 Current TO 800 PM Current TO 730 PM Denver County 1 Current TO 800 PM Current TO 730 PM DIA 1 Current TO 800 PM Current TO 730 PM Arapahoe County 1 Current TO 800 PM Current TO 730 PM the City of Aurora 1 Current TO 800 PM Current TO 730 PM Arvada 1 Current TO 800 PM Current TO 730 PM Wheat Ridge 1 Current TO 800 PM Current TO 730 PM Lakewood 1 Current TO 800 PM Current TO 730 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Arapahoe Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Boulder Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Broomfield Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Denver Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Douglas Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Jefferson Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Foothills above 6500ft       Boulder Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Douglas Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW Jefferson Current TO 900 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (20%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]