Flash Flood Prediction Program

Time: 1049 AM Sun June 4, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SATURATED SOIL AND PERSISTENT NON-THUNDERSTORM RAIN IS RSEULTING IN RISES OF SMALLER CREAKS AND STREAMS Wave after wave of persistent non-thunderstorm rain continues to move into the District and will do so over the next several hours. These showers have generally been between 0.1-0.3” per hour type storms, with some isolated areas just over 0.5” in 60 minutes. Storm motions have been nearly due east to west, with relatively fast storm motions, which has helped limit point rainfall amounts. However, this persistent moderate to brief heavy rainfall across the District has led to some minor creek and stream flooding already and will likely increase as soil saturation levels are at their peak. Very little moisture will be able to soak into the ground as we head into the afternoon, which will likely lead to areas of pooling, especially in poorly drained areas. If rainfall rates increase and approach the 1"/hr threshold or thunderstorms become more likely this afternoon, then Message 1's may be issued. Rainfall will continue well into the afternoon and evening with moderate to heavy showers slowly tapering off this evening. Rainfall chances will likely continue into the late evening hours, with a very slight chance for scattered off and on showers through the overnight. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers will produce 0.2-0.7” in 30-60 minutes. A moderate to heavy rain shower, or thunderstorm could produce 0.7-1.3” in 30-60 minutes. WORST CASE SCENARIO: An anchored thunderstorm, or training of moderate to heavy showers has the potential to produce up to 2.6” in 60 minutes. A LOOK AHEAD: This unusual pattern will finally start to break down tomorrow as upper-level flow shift back to a more typical west to east pattern. A chance will remain for showers and thunderstorms tomorrow, however drier air from the NW should help limit the available moisture, effectively decreasing the chances for heavy rainfall. Next week will resume a more seasonable pattern with high temperatures back into the 70’s along with afternoon/evening rain/isolated thunderstorm chances through the week. LOCATION PRIME TIME 60-Minute Rainfall and % Probability Message Potential Plains       Adams Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Arapahoe Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Boulder Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Broomfield Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Denver Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Douglas Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Jefferson Current TO 1000 PM SUN 0.2" (80%) to 0.7" (50%) to 1.3" (30%) MOD Foothills above 6500ft       Boulder Current TO 1000 PM SUN 0.2" (90%) to 0.7" (60%) to 1.3" (30%) MOD Douglas Current TO 1000 PM SUN 0.2" (90%) to 0.7" (60%) to 1.3" (30%) MOD Jefferson Current TO 1000 PM SUN 0.2" (90%) to 0.7" (60%) to 1.3" (30%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]