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417 FXUS65 KBOU 210644 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1244 AM MDT Fri Aug 21 2026 .KEY MESSAGES... - Hot today with high temperatures pushing 100F over portions of the plains and I-25 Corridor. - High-based late afternoon and evening showers/storms/virga producing gusty microburst winds, with a few strong to severe storms possible for the far eastern plains. - Monsoon moisture returns this weekend and holds into early next week, with increasing chance of storms and slightly cooler temperatures. && .DISCUSSION /Through Thursday/... Issued at 133 PM MDT Thu Aug 20 2026 A warmer and drier airmass is taking hold today as the ridge starts to amplify over the Four Corners into the Great Basin. We still have enough moisture per current satellite imagery for a few showers and weaker storms in the mountains, mainly south of I-70. Those will end early this evening as the airmass stabilizes, while the plains will remain too dry and stable for any convective activity. Overnight lows will be several degrees above normal. On Friday, we`ll be back to the frying pan as the thermal ridge shifts eastward and centers itself across Colorado. 700 mb temperatures warm a couple more degrees C, which supports highs in the mid to upper 90s across the plains and I-25 Corridor, with a few spots nearing 100F from downtown Denver to Greeley and Fort Collins. The record for tomorrow in Denver is 99F set in 2023, and we should be very close to that at the official reporting station. Those readings also bring us very close to Heat Advisory criteria, but most locales should stay just below 100F. There will be some heat relief in the form of high based convective clouds late in the day as mid/upper level moisture starts to spread into the region. Given large DCAPE of 1500-1700 J/kg and deep inverted-v profiles, strong microburst winds to 50+ mph will be possible from any high based showers. For the weekend, ensembles are still showing the upper level ridge axis to shift slowly eastward or flatten, with the flow aloft trending more westerly. This will allow for an uptick in monsoonal moisture across the forecast area, leading to scattered thunderstorms each afternoon. In these moisture and flow patterns, the most numerous storms are expected over the mountains and eastern plains. Meanwhile, the majority of the storms along the I-25 Corridor will be higher based as the airmass is still quite warm and low level moisture is expected to be lacking. But given the uptick in precipitable water to near 150% of normal, that still doesn`t mean we can`t see locally heavy rainfall. There may be some change in this pattern as flow turns slightly more west-northwesterly toward Tuesday or Wednesday. That could allow for a weak backdoor front or two with increasing low level moisture, but plenty of uncertainty exists here with respect to timing and intensity of any surge(s). In any case, it appears temperatures will settle a little closer to (still above) normal for this weekend through much of next week. And enough moisture will be around to keep a chance of storms in the forecast most days. && .AVIATION /06Z TAFS through 06Z Saturday/... Issued at 1207 AM MDT Fri Aug 21 2026 Southerly drainage winds have settled in at KDEN and KAPA late tonight, with light and variable winds in place at KBJC. Expecting winds to become slightly more southwesterly at KDEN/KAPA by 13Z to 14Z, with KBJC holding onto a light northwesterly flow by around 10Z tonight. Winds are expected to transition to the NNE at KDEN/KAPA by 18Z-19Z, with KBJC being slightly more NE. The main concern for today continues to be with the potential for high-based showers capable of producing gusty outflows and some dry microbursts. Despite the low potential for any precipitation (~15% chance) at any of the TAF sites, there will be ample amounts of DCAPE in the area that will support some strong microbursts as showers move off the higher terrain through the afternoon. Even if showers do not pass directly over the TAF sites, gusty outflows are expected to impact the TAF sites, bringing potential for multiple wind shifts through the afternoon, with gusts up to 30-40 kts possible. The greatest coverage in showers looks to be north of the TAF sites in the afternoon, that will aid in keeping winds more northerly, but certainly can`t rule out wind shifts from other directions where showers develop. A PROB30 remains in all TAFs to account for this. As showers progress eastward in the evening, winds should turn to the east before turning to the south and then drainage for the overnight. We can`t rule out a few easterly outflows making it back to the TAF sites through the evening, as a few stronger storms are expected to develop over the eastern plains. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...20 AVIATION...9