National Weather Service Forecast Discussion |
Thornton Weather Forecast Today's Forecast Story |
153 FXUS65 KBOU 030838 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 238 AM MDT Thu Sep 3 2026 .KEY MESSAGES... - Warmer Thursday and Friday with mainly dry conditions. - Return of better moisture by the weekend with an increasingchance for showers and thunderstorms. - Still no significant pattern change on the horizon, with above normal temperatures continuing into next week. && .DISCUSSION /Through Wednesday/... Issued at 133 AM MDT Thu Sep 3 2026 Generally dry southwesterly flow aloft continues today. The main players of the week - a strong closed 500mb low over the Pacific Northwest, and a broad ridge centered across the central/southeastern CONUS - won`t do much over the next 24-48 hours. For Colorado, that means most of the state will remain relatively quiet over the next couple of days. Mid-level temperatures near 14-17C today and tomorrow will likely lead to high temperatures in the low 90s. The overall synoptic pattern favors the development of a Denver cyclone today, and there may be some minor temperature gradients across the metro depending on where that sets up. While a couple of CAMs and REFS members attempt to develop a shower or two near the convergence zone of the cyclone this evening, that probability remains rather low (~10%). Friday looks to be a similar story, though we should start to see some gradual moisture advection into the region by the afternoon and evening, leading to some scattered showers and thunderstorms across the higher terrain... especially along/south of I-70. As we approach the weekend, the ridge is expected to build across the Central Great Plains, while the upper trough remains nearly stationary over western Washington/Oregon through at least Sunday. That gives us a couple of days of fairly well aligned southerly or south-southwesterly flow aloft, which should allow for a fairly robust plume of moisture to stream into the region... perhaps even advecting in some moisture from the now-Hurricane Marie. While the increase in moisture should allow for widespread showers and storms across the higher terrain, the absence of any meaningful synoptic scale forcing will likely limit the amount of precipitation across the plains, where thunderstorm chances would be driven by a myriad of mesoscale influences. Moisture is expected to hang around through Monday, but the ridge is expected to expand a bit further west by sometime early next week, shifting the flow aloft towards the west-southwest. Forecast uncertainty quickly increases by mid-week. Across the 00z ensemble suite, it`s close to a 50/50 split on maintaining a good moisture feed into the state. However, there is a rather robust signal for above normal temperatures to continue for the foreseeable future. The last couple cycles of the ECMWF (along with the AIGEFS and ECMWF AIFS ensemble) keep high temperatures in the 80s to low 90s over the next several days, with no real hint of a substantial pattern change anytime in the next 7-10 days. && .AVIATION /06Z TAFS through 06Z Friday/... Issued at 1135 PM MDT Wed Sep 2 2026 VFR through the TAF period. Drainage winds are expected tonight through the first half of Thursday. Main concern in this TAF period will be the potential for a Denver Cyclone to develop near the terminals late in the afternoon. Guidance still varies in the definition of this feature but most feature some sort of cyclone or shear zone, leading to a lower confidence wind forecast. A few models also try to develop a brief shower or storm along this convergence during the evening. A PROB30 may eventually be needed but would like to see better agreement from CAMs overnight. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hiris AVIATION...Hiris