Inversion Forecast
Update 11/10/2025: Overview: A bea-utah-ful start to the work week as a strong ridge of high pressure translates through the region. The persistent Aleutian Low will continue to present the Western U.S. with another low pressure storm system, with the next round expected to sweep through later this week. Inversion ingredients remain limited through the short term forecast while a forecast weather pattern towards the end of the month presents more long-lived inversion conditions. We await for the critical ingredient, valley snow cover, before feeling too serious about inversion impacts. Short-term (Mon. Nov 10 - Friday Nov 13): While strong high pressure translates through the early half of the work week, shallow overnight surface inversions seem to be sufficiently mixed during daytime heating to keep from accumulated multi-day impacts at the surface. Large scale mid-level inversions seem to be the only concern this current ridge of high pressure offers. Long-term (Weeks 2-3): The active Aleutian Low should continue keeping offshore storm conditions present through much of the month of November. Current extended range forecasts keep Utah on the periphery of most of that focus but close enough that inversion conditions should remain limited. Towards the end of the month, the weather pattern flips and an offshore ridge of high pressure becomes the persistent feature. This stretch of conditions would present more inversion-favorable large scale conditions, however, more surface-level ingredients are needed before we start to expect to see the classic winter inversion set up. Until snow cover and more arctic air masses set up to move through the region, impacts from inversion should remain minimal.
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.