National Weather Service Forecast Discussion |
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243 FXUS65 KBOU 211121 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 521 AM MDT Sun Jun 21 2026 .KEY MESSAGES... - Strong to severe storms possible across the far eastern plains today. Otherwise, temperatures holding steady with elevated fire weather conditions in the high country and some patchy smoke aloft from wildfires in Utah. - Increasing coverage of afternoon thunderstorms early to mid week, with continued potential for severe thunderstorms, especially in the plains. - Slightly moderated temperatures midweek, with drier and warmer weather returning for the weekend. - Elevated to at times locally critical fire weather conditions will persist much of the week in the high country. && .DISCUSSION /Through Saturday/... Issued at 105 AM MDT Sun Jun 21 2026 Stratus has become relatively widespread across the lower elevations in the wake of yesterday`s front, though should largely remain elevated enough to keep any dense fog patchy in nature, more prevalent over the higher elevations of the Pawnee Grasslands. Cross-sections point to a fairly early mixing of westerly and southwesterly flow this morning which should help dissipate lingering stratus shortly after sunrise. Mostly elevated smoke will also be present at times today, stemming from ongoing wildfire activity in western Utah. Today`s convective forecast remains on track, with a modest dryline progged to settle in our eastern plains and allow for an axis of greater instability this afternoon/evening across our easternmost tier of counties. Shear doesn`t appear to be overly impressive, but a few pockets up to around 40 kts look to be present in the plains. Wind and hail will be the primary severe weather threats in the plains today. Farther west, drier air will be in place through ~500mb under weakly subsident flow, hindering instability and precipitation chances. Some virga and isolated showers will be more likely for the urban corridor, along with a few gusty outflows. Temperatures look to hold steady under the subsident pattern. In the mountains, lingering breezy and dry conditions will sustain elevated to near-critical fire weather conditions. Another weak shortwave arrives Monday, with the dryline experiencing a westward nudge and PW values climbing to between 0.80-1.00" for most of the plains. Despite a slight cooldown, elevated dewpoints will promote increased instability and thus greater thunderstorm coverage for the lower elevations, including the I-25 corridor. Still, the higher potential for severe convection will remain over the rural plains. In the high country, gusty west winds resulting from strengthening zonal flow will lead to near-critical and potentially critical fire weather conditions for some locations. Moist easterly flow will remain anchored in place Tuesday into Wednesday, maintaining at least scattered afternoon showers and thunderstorms for most of the area as well as cooler temperatures despite some height rises aloft. Precipitation chances for the urban corridor look to be the highest during this period, and may extend into Thursday depending on how quickly the pattern evolves. A warming and drying trend is favored as we head towards the weekend, with ensemble means indicating healthy potential for temperatures climbing into the mid/upper 90`s for the lower elevations by Saturday. && .AVIATION /12Z TAFS through 12Z Monday/... Issued at 512 AM MDT Sun Jun 21 2026 Low stratus has retreated east of the I-25 corridor including KDEN, with only localized patchy stratus lingering in a few locations. Given current wind directions, see little reason for stratus to rebound west with any significance, so have proceeded with maintaining all terminals under VFR conditions for the remainder of the TAF period. Of note however, light to moderate concentrations of wildfire smoke from Utah do look to persist particularly through the morning hours, most likely between the 050-080 levels, which may impact slantwise visibility at times. Winds are expected to turn NW/N with daytime mixing, although have pushed the breezier conditions back by 1-2 hrs considering typical overmixing biases in model guidance. Winds will continue turning clockwise through the afternoon and eventually return to drainage this evening. Convection is anticipated to remain east of all Denver area terminals today given minimal instability over the urban corridor and dry low-levels, although isolated virga and outflows cannot be ruled out for any of the terminals. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...BRQ AVIATION...BRQ