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790 FXUS65 KBOU 111813 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1213 PM MDT Tue Aug 11 2026 .KEY MESSAGES... - Hot temperatures to continue this afternoon, then start to cool tomorrow and fall below normal Thursday. - Another round of high-based virga showers this afternoon. Wind gusts of30-40 mph are possible from the showers. - Monsoon moisture becomes plentiful beginning Wednesday afternoon bringing daily rounds of showers and thunderstorms through the rest week and weekend. Locally heavy rainfall and flash flooding may occur. && .DISCUSSION /Through Monday/... Issued at 417 AM MDT Tue Aug 11 2026 The upper-level high previously centered over the Four Corners has begun to dissolve, and as such, flow aloft will remain zonal and weak today, continuing to allow a bit of monsoonal moisture to seep into the Desert Southwest and parts of Colorado. The better afternoon shower coverage will reside over the high terrain. However, with model soundings over the Denver metro and eastern CO plains showing inverted-V soundings and DCAPE values ~1200 J/kg, virga showers will still be able to produce strong outflow winds up to 40 mph even with little precipitation reaching the surface. We expect afternoon highs to reach the mid 90s over the Denver metro, with a few 100s possible over the eastern Colorado plains. If increasing moisture over the region Tuesday evening is able to keep clouds around through most of the night, morning lows on Wednesday may only reach the mid 60s across the low elevations. Monsoonal moisture transport ramps up on Wednesday as the upper level ridge redevelops to our east with the accompanying high centered over the southern U.S. plains. This pattern change will moderate afternoon highs to near-normal on Wednesday, and much cooler than normal Thursday through Saturday (low 80s across the low elevations). Additionally, an upper level trough will begin to take shape just off the coast of California. From a synoptic standpoint, the combination of the trough off the Pacific coast and the ridge over the south-central Plains will help channel Pacific moisture into the Four Corners and provide a classic monsoonal setup. Shower coverage will become widespread on Wednesday starting over western Colorado in the late morning and spreading over the Front Range, foothills, and eventually the Denver metro and eastern Colorado as the day progresses. Locally heavy rainfall may also occur with the strongest showers and storms. Precipitable water (PW) values on Wednesday will rise to around the 90th percentile of climatology (0.97"). However, shallow warm cloud layers and storm motion vectors ~20KT will limit flash flooding potential. Moisture is projected to peak on Thursday afternoon as mid level Pacific moisture and low level Gulf moisture give way to PW values that are 150%-200% of the climatological average (~1.4"). From a flash flood mesoanalysis perspective, a relatively deep warm cloud layer (~5,000 ft), slower storm motions (LCL-EL mean wind ~15KT), and a long-skinny CAPE profile will lead to conditions that are favorable the production of efficient rainfall. If this forecast trend continues, flood watches for flash flooding concerns may need to be issued in the next 48 hours, once the footprint of the heaviest precipitation becomes more clear. Additionally, if the rainfall on Wednesday overperforms, areas with increased soil moisture may be more prone to flash flooding on Thursday. For Friday, PW values will still greatly exceed the 90th percentile of climatology and a shortwave trough may provide additional forcing for showers and storms. Faster storm motions will limit flash flooding potential unless heavy rainfall occurs over areas with near- saturated soils from the previous day`s rain. Long-range model ensemble members suggest a slight decrease in moisture for the weekend, although most solutions still show PWs in the 1.0-1.2" range due to continued southwest flow aloft. We are fairly confident that there will be daily chances for precipitation each afternoon through at least early next week. Ensemble spread does suggest uncertainty entering the picture halfway through next week, although near-average monsoonal moisture still favors afternoon showers over the high terrain on most days. A warming temperature trend will begin on Monday, with 90-degree afternoon highs over the Denver metro becoming likely late next week. && .AVIATION /18Z TAFS through 18Z Wednesday/... Issued at 1139 AM MDT Tue Aug 11 2026 Current light and variable winds are expected to make a more northeasterly transition in the next hour, before a more northerly component is expected for the afternoon. The main concern for today will be with high-based showers around the TAF sites. While there is higher confidence in microburst potential just outside of the TAF sites, there remains a threat for outflows from showers outside of the TAF site`s immediate area passing over and initiating something over the airfields. There is higher confidence that we see a few hours of variable winds from passing outflows bringing wind shifts between 25-30 kts, than direct impacts from microbursts directly over the TAF sites, with KBJC having the best chances for microburst and light precipitation. Confidence is on the lower side for an immediate transition to drainage winds by 3Z, with potential for a few hours of light and variable winds possible between 3Z-6Z depending on where any lingering showers/outflows remain. Once drainage winds settle in, they are expected to remain in place for the overnight hours, with KBJC remaining slightly more westerly than SW like KDEN/KAPA. Ceilings are expected to remain at or above 10,000` AGL through this afternoon and evening. Moisture is expected to increase for Wednesday, with higher confidence in showers or some weak storms passing across the TAF sites. Expecting winds to be slightly stronger tomorrow, with potential for some stronger to severe storms developing just east of the TAF sites in the afternoon/evening. Have introduced a TEMPO starting at 20Z at KDEN, but KAPA/KBJC could see impacts slightly sooner. Smoke continues to linger along the Front Range that may impact slant range visibility, but it does seem to be gradually improving. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...AA AVIATION...9