Update 02/13/2023: Synopsis: Inversions will persist to start the workweek, while an impending strong cold front brings inversion-clearing conditions through the middle of the work week. Extended range forecasts suggest no major high pressure ridge development, so the inversion tool here will not predict inversions, but clear and cold conditions and no major active storm systems will likely lead to weak to moderate inversions re-establishing later this week and into the weekend. Short-Term (Feb 13 to Feb 16) Tuesday and Wednesday should see the current inversions mixed out during the strong cold front and subsequent precipitation event. Lack of dominant high or low pressure systems following this impending system lowers forecast confidence, however, the safe bet lies in a return of inversions to some degree as long as snow cover remains and cold air occupies the region. Long-Term (Feb 17 to end February) Limited inversion probability from this tool is primarily a function of the zonal (i.e flat) western U.S. weather pattern predicted over the next two weeks. Such a scenario greatly complicates the inversion prediction toolset, however, as we've seen numerous times this season, the presence of substantial snow cover, clear skies and cold air masses is more than capable of setting the stage for inversions without the large-scale forcing from a long-lived ridge of high pressure. As such, our long term inversions expectations remain favorable despite the inversion's predicted probably appearing to suppress inversions. The net effect of the forecast weather pattern would favor at least short term, mild to moderate inversions.
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.