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405 FXUS65 KBOU 181132 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 532 AM MDT Mon May 18 2026 .KEY MESSAGES... - Rain and mountain/foothill snow increases in coverage this morning with much colder temperatures arriving. - Accumulating snow for the mountains and the foothills. Only a few wet snowflakes possibly mixed in for the I-25 Corridor. - One last spring freeze possible on some of the plains Monday night. - Delay in the warming and drying trend for the week ahead, but still warmer and drier by Friday - next weekend. && .DISCUSSION /Through Sunday/... Issued at 1222 AM MDT Mon May 18 2026 An upper level trough over the Great Basin will move across the area on Mon with favorable mid level ascent thru the aftn hours. At the sfc, upslope flow will be in place which will combine with the upper level trough to produce widespread precip across the area. Snow will occur in the mtns and higher foothills with several inches of accumulation. Have upgraded areas north of I-70 in the mtns to a warning as east facing slopes could see from 12 to 18 inches in some areas. Elsewhere will keep amounts in the advisory range. In the foothills, some of the higher areas may see 4 to 8 inches above 8000 ft with lessor amounts below 8000 ft. By Mon night precip should gradually decrease over the area during the evening hours. Overnight lows late Mon night into early Tue morning may drop down to freezing or slightly below across portions of the plains. For Tue, a disturbance will move across the area late in the aftn thru Tue night. As this feature moves across, there will be another round of precip over the higher terrain and across portions of the plains. Highs on Tue will remain cool as readings stay in the 50`s across the plains. Looking ahead to Wed, an unsettled pattern will continue as decent lapse rates will combine with lingering moisture to produce a good chc of showers and thunderstorms over the higher terrain and portions of the plains. Most of the activity will occur in the late aftn and early evening hours. Highs will remain below normal as readings only reach the upper 50`s to mid 60`s across the plains. By Thu into Fri, latest data shows another upper level trough moving southeast towards the area. Not sure about the timing of this system, however, as it moves across should see another good chance of showers and thunderstorms. Temperatures both days will be in the mid 60`s to lower 70`s across the plains. For next weekend, will see a return to a drier and warmer pattern based on latest data. && .AVIATION /12Z TAFS through 12Z Tuesday/... Issued at 518 AM MDT Mon May 18 2026 Ceilings are currently bouncing between 300ft and 600ft at the TAF sites. These IFR and LIFR conditions are expected to continue through the rest of today and into tomorrow morning. Scattered light rain showers this morning will increase in coverage late this morning and early this afternoon, leading to multiple hours of rain showers and a few thunderstorms. Coverage should start to decrease near the TAF sites around 21Z to 23Z, leaving some scattered showers for the late afternoon and evening. Rain chances will decrease for the overnight period, but there still is a low chance (051. && $$ DISCUSSION...RPK AVIATION...AP