Inversion Forecast
Update 01/15/2026: Overview: Inversion conditions persist through the end of the weekend as the potential weak disturbance we were hoping would clip northern Utah is now predicted to move through the Dakotas. Worse air quality has developed in the recent 36 hours, leading to unhealthy categories of air quality populating most Northern Utah valleys. A potential for yet another week of inversion conditions is still on the table as we look to the end of next week for the next storm system to move through. Time will still be needed to monitor the track of the forecast storm as not all models capture it's presence in the Great Basin. Short term: Fully entrenched inversions populate northern Valleys with little relief expected over the weekend and potentially deeper into next week. The ridge of high pressure should release it's grip on the western U.S. as it displaced into the Gulf of Alaska, However, it's displacement won't noticeable alter Utah's inversions until we can see a storm system move through. For now, inversions will continue. Long term: The extended forecast continues to look for week 2 improvements, however we've recently seen those weather patterns fall apart as they enter week 1. For now, the large-scale weather pattern will remain dominated by stable conditions in the atmosphere. Models begin to hint at the potential for a weak system to clip the region by the end of next week, but the pattern isn't ideal to keep confidence high at this point. Wishcasting will take the form of this discussion while we wait for more model agreement on the position and strength of the end of January's weather pattern.
This product is being developed by researchers at the Utah Climate Center. Using output from the National Center for Environmental Prediction’s (NCEP) Climate Forecast System (CFSv2), this technique projects surface inversion probability for persistent inversion events—defined as events lasting longer than 4 days—with a demonstrated “skill” over a span of ~ 30 days. A surface inversion probability of 35% or greater suggests a statistically significant likelihood of an extended event. It should also be noted that inversion forecasts, in and of themselves, are not air quality projections. The projection is valid for a radius of roughly 200 miles around Salt Lake City.
Image Interpretation: The blue bar graph shows the calculated Surface Inversion Probabilities. Values above the horizontal yellow line (~35% on the right axis) have a statistical significance of manifesting as persistent (> 4 days) inversion events. The solid black line above the SIP chart shows the ensemble average of 200mb geopotential heights for the most recent 16 CFSv2 forecasts. The individual dotted lines are individual model runs. The vertical red and yellow lines identify the initialization (+0) and 30 day (+30) locations. SIP values lying within this 30 day window have a statistically significant confidence interval. Values before the initialization data are obtained from NCEP reanalysis data.
For more information on the methodology and origins of this product, see the following publication here.