Inversion Forecast

Update 12/02/2025: Overview: Low elevation snow has finally arrived, setting the stage for daily inversions, however the weather pattern is not expected to present the large-scale ingredients for long-lived inversions through the upcoming week. Weak inversions and moderate air quality measurements as of this morning suggest the cold air and snow cover is offering minor short-term impacts but should remain well mixed through the short term. The long-range guidance agrees on the development of an east Pacific ridge but mixed on the position. Ultimately, this position will determine the West Coast storm track (or lack there of) and whether longer term inversion conditions present on top of the shorter term bottom-up inversion ingredients. Short term: Synoptically, the large-scale pattern will limit inversion impacts, as captured by the forecast graphic. The mid-week disturbance currently prepared to sweep through will help keep airsheds well mixed. Headed into the weekend, Utah sits in between the upstream ridge and downstream trough with models mixed on how heights will trend overhead with GFS suggesting falling heights and CFSv2 suggesting a fairly neutral trend. Long term: Ultimately, the lack of model agreement on the positioning of the eastern Pacific ridge presents uncertainty on how the next few weeks will position inversion ingredients. Across most model solutions, the ridge remains upstream enough to limit the long-lived inversion ingredients this tool is attempting to capture. The position and stability of the ridge seems enough to remain on the outskirts of large-scale conditions for higher impact inversions, but cold air will be on the doorstep with the northwesterly prevailing pattern in place. Such conditions might very well introduce short-term inversions if the ridge wobbles east and shifts farther over the western U.S.