Colorado Weather Forecast | Sep. 8–12, 2021
Dry, hot, and smoky. Isolated thunderstorm chances and less smoke this weekend.
Hello everyone. A summer-like pattern has firmly established itself across the western United States, with heat building under a strong subtropical high that is centered over the Intermountain West.
This may not really break down until next week or later, but a few disturbances will push through over the next week which will bring moisture and cooler temperatures at times.
As we discussed in length over the holiday weekend, our primary concern with this pattern was smoke. While the high pressure system set up just differently enough from model expectations to spare us an initial wave of heavier smoke (this weekend ended up being pretty decent in terms of air quality — sorry if you changed plans because of the smoke that never really came!), the heavier stuff has been slowly rotating around the center of high pressure and is now entering Colorado.
PM2.5 Air Quality Indices are pretty dismal across the state, with the urban corridor approaching Unhealthy levels today.
Smoke should get worse for most of the state into tomorrow and stick around in heavier quantities through Thursday, though a very weak cold front for the Front Range this evening could help mix some of the surface-level smoke out a bit — maybe? It could also just as well push more smoke against the mountains and further deteriorate air quality at least along the urban corridor. As we’ve been seeing this year, smoke models can be helpful on a larger scale, but the details are often elusive.
The good news is that by Friday, the center of high pressure should move more than far enough east to allow cleaner air to start working its way into the state.
Until the weekend, the other main story is the heat. Denver has a good shot of breaking its record high temperatures for September 9th and 10th (Thursday and Friday of this week). The record is 94 and 93 degrees, but the Blend is forecasting highs of 95 and 96 degrees for both those days. The low 90s seem to be possible this weekend and even next week at times, so despite Labor Day being the “unofficial start of fall” it’s really going to feel anything but.
The atmosphere is currently very dry over Colorado, but some moister air returns by Friday as a very weak shortwave tracks from west to east well north of the state, helping advect a decent pocket of moisture into the state by the weekend.
Despite the increased moisture, the level of subsidence under the powerful dome of high pressure over our region will likely suppress storm development, and we see only isolated afternoon thunderstorm chances in the forecast at best.
Monday looks to be another hot and dry day but our next disturbance arrives Tuesday / Wednesday in the form of another trough/tropical storm combo. If the trough ends up being the prominent feature, we could see decent high-elevation snow in the forecast for mid-next week. Otherwise, we may just see a bit of a temporary cooldown and some isolated thunderstorms.
Oh yeah, fall colors are starting to make an appearance, though not on a large scale yet. We think peak fall colors should appear around their usual time, though the best colors may be arrive a bit earlier than usual in the Park Range (Steamboat), Sawatch, Gores, and parts of the San Juans.
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