Inversion Forecast
Update 02/24/2025: Summary: A stretch of drier and warmer weather conditions will suppress inversions despite having valley snow cover spread across northern Utah. Warming temperatures this week will likely melt what remains at low elevations, further limiting the inversion ingredients at play as the weekly weather pattern is influenced by high pressure. Mild haze is still a possibility during this week, but impacts should remain marginal thanks to the warmer temperatures. Short-term (Feb 24 - Feb 28): A mid-week grazing shortwave disturbance looks to be the only weather feature of interest over the short term, so if any mild inversions do develop, the question will be is the passing disturbance strong enough to mix out inversion conditions. A stronger, but not long-lived return of high pressure looks to conclude the month of February. Long-term: (Early March): As the inversion season begins to conclude thanks to warming air, melting snow, and longer days, an active weather pattern should continue to place the storm track through the region, although much of the storm ingredients aren't too impressive within this storm regime. Most common are cut-off lows spinning through the southwest, which would help keep any 11th hour inversions this season at a minimum--although just as frequently will be a ridge of high pressure set up across the west. Such a set up carries a great deal of local impact uncertainly, but favors limited inversion conditions as we conclude the season and look forward to spring.
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.