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852 FXUS65 KBOU 201902 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 102 PM MDT Wed May 20 2026 .KEY MESSAGES... - Unsettled through Thursday, with a few strong to severe storms expected in the plains late Thursday. Lingering showers into Friday, mainly south of I-70. Remaining cool. - Warmer and drier this weekend, with isolated showers possible Saturday afternoon. - Remaining mild next week but with a return of potential afternoon showers and thunderstorms. && .DISCUSSION /Through Wednesday/... Issued at 1225 PM MDT Wed May 20 2026 Our ongoing pattern of unsettled weather continues marching along. Additional beneficial precipitation was observed last night and into this morning aided by upslope flow and jet-induced lift, with bands focused south of I-70 for the most part, and the higher elevations of Park County receiving over 6" of new snow. The responsible shortwave will lift northeast through the remainder of the day, merging with the broader synoptic flow but maintaining modest lift over the plains this afternoon. We`re beginning to see some redevelopment of showers across the high country associated with the passing shortwave, and these will gradually spread into the lower elevations through the afternoon. As of this writing (~12 PM Wed), ACARS soundings from Denver International Airport still snow a capped environment near the 700mb level, hindering shower development. However, this should erode in the coming hours and allow for more expansive coverage across the urban corridor and plains with a few embedded thunderstorms. Instability is quite marginal today and generally peaking at under 400 J/Kg for most locations, so severe thunderstorms are not anticipated. Activity looks to exit our eastern plains late this evening. On Thursday, a second shortwave will develop over western Wyoming, traversing our area overnight. Ahead of it, a moderately moist airmass will remain as a well-defined Denver cyclone sustains south and southeast flow over the plains, with some warm advection in place as well. Low-level lapse rates look to steepen notably, promoting higher ML CAPE values over 800 J/Kg by mid-afternoon, mainly east of I-25. Bulk shear locally in excess of 50-60 kts would support development of a few discrete supercells late afternoon and into the evening for the plains, with much of the convective activity likely initiating/intensifying with the convergence boundary associated with the Denver cyclone mid- afternoon. Large hail will be the primary threat from any strong to severe storms, with a lesser but nonzero potential for strong outflows and a few landspouts. Thunderstorm activity will linger later into the evening than is typical, fueled by the passage of the trough axis, and waning more noticeably behind the front after midnight. In the eastern plains, a few locations may pick up 1-2" of rain with the heaviest cells, especially given the potential for successive storms. Slightly cooler temperatures can be expected for Friday following the nocturnal front, with highs generally around 10 degrees below average. This also implies a more stable environment, with limited opportunity for thunderstorm development. Nonetheless, northeasterly upslope flow will still allow for some afternoon showers and perhaps an isolated storm or two primarily over the southern foothills and Palmer Divide. Precipitation chances will be much lower elsewhere. A warming trend returns for the weekend, and we may be scraping the 80`s for the lower elevations come Sunday. With a third weak shortwave in the mix on Saturday and some marginal instability in place, some isolated afternoon showers and weak thunderstorms will be possible (20-50% chance, highest for the Palmer Divide). Not so much the case for Sunday, when most if not all areas look to stay dry. Opportunities for more afternoon convection will return next week as a troughing pattern becomes more established to our west. && .AVIATION /18Z TAFS through 18Z Thursday/... Issued at 1210 PM MDT Wed May 20 2026 Current observations show a Denver cyclone set up just to the west of KDEN. This cyclone is expected to shift southward over the next few hours leading to N/NNE winds by early this afternoon at all three sites. Current radar shows showers ongoing to the west of KBJC in the mountains. There is still strong agreement that showers and storms should move in from west to east affecting all three terminals this afternoon starting as early as 19z and lasting into the early evening. Visibility could lower to MVFR or IFR at times as this rainfall moves through. Otherwise, winds will shift around to drainage by this evening at all three TAF sites. Low clouds are expected to continue overnight given the presence of deep low- to mid-level moisture. For tomorrow, a Denver cyclone is forecast to setup near/over KDEN once again. The evolution of this feature will in turn affect the SHRA/TSRA chances. For now, we expect showers and storms in the vicinity of the terminals by around 19z to 21z. These showers and storms should last well into the evening. We have left out any mention of -TSRA for now, but there is a chance (15-20%) given the decent instability expected. Visibility could once again lower to MVFR or IFR at times as this rainfall moves through. There is also the possibility of some breaks in the clouds, especially in the afternoon tomorrow at KDEN, so have raised ceilings to around 12,000 ft AGL for now. Finally, gusty winds are possible tomorrow afternoon with any storms that do move near the three sites. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...BRQ AVIATION...MV