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252 FXUS65 KBOU 211733 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1133 AM MDT Mon Sep 21 2026 .KEY MESSAGES... - Cooler conditions continue Monday, with more limited shower and thunderstorm coverage. - Gradual warming returns Tuesday, with generally isolated precipitation chances each day. && .DISCUSSION /Through Sunday/... Issued at 1215 AM MDT Mon Sep 21 2026 Current radar imagery shows a few strong thunderstorms lingering over Elbert and Lincoln counties as well as a couple of weak showers over the northern Colorado plains. Any storm that is able to strengthen over the next hour or two will be able to produce large hail and torrential rainfall. However, we believe the severe thunderstorm threat to be nearing its end for the night as mesoanalysis shows an overworked atmosphere and decreasing CAPE. Areas of patchy fog will likely develop due to the low level moisture left over from today`s convection and small dewpoint depressions. Monday afternoon looks to be fairly quiet as a weak ridge builds over Colorado and subsidence gives way to mostly sunny skies. Temperatures will remain slightly cooler than normal, with afternoon highs mainly in the low 70s at low elevations, and 50s-60s for the mountains. Model guidance suggests a weak shortwave grazing southeast Colorado Monday night as well as an increase in wind speeds at the 700mb level. Given the slightly above normal moisture already in the environment, few sprinkles over the plains cannot be ruled out late Monday night into Tuesday morning. The upper level ridge tracks east and flow aloft turns southwesterly on Tuesday. At least a few isolated showers seem possible over the high terrain due to the slight uptick in monsoonal moisture, with the plains remaining dry. One point of uncertainty for Tuesday is that model guidance suggests breezy southerly winds over eastern Colorado/western Kansas which could lead to a richer atmosphere for storm development, although instability should remain fairly limited. A disturbance will track north from New Mexico onto Colorado on Wednesday, which will bring a better chance for showers and storms over the eastern Colorado plains in the late afternoon and evening. The mountains will see an increase in shower activity Wednesday afternoon as well, but it remains unclear whether any showers from the foothills would survive and make their way onto the Denver metro or if low level moisture will be transported west enough. Moisture will generally remain above normal through the entire forecast period, and models have been consistent in bringing precipitable water values that are at least 150% of normal to the region Wednesday through Friday. However, given the cooler temperatures expected to be in place, lifting mechanisms will be needed for meaningful rainfall to come to fruition. && .AVIATION /18Z TAFS through 18Z Tuesday/... Issued at 1129 AM MDT Mon Sep 21 2026 VFR conditions are expected to prevail through the TAF period. Day cloud phase satellite shows a small patch of cumulus near DEN/APA, with cloud bases somewhere between 2-4kft AGL. While a FEW-SCT deck may continue for a couple more hours, guidance generally lifts/dries out any remaining boundary layer moisture. Winds should remain light today with a prevailing direction out of the east. Winds should slowly turn clockwise this afternoon and evening before settling on drainage overnight tonight... before weakening and becoming more variable Tuesday morning. Depending on how much surface moisture/instability is available in the afternoon, there could be a few showers or thunderstorms near the terminals by mid/late afternoon Tuesday. Instability looks weak enough to only carry a PROB30 for SHRA at this time. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...AA AVIATION...Hiris