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    Inversion Forecast


    Discussion Last Updated: 02-08-2017 5:31:49 pm MST

    A warm and wet weather pattern looks to dominate the western U.S. through the second week of February. Unfortunately, that does not mean inversions are over. The mean circulation of the upper atmosphere over northern Utah will remain in a state of ridging through the middle of the month. While warm pacific moisture has been streaming across the northern valleys, inversion conditions will quickly reform toward mid-month in the wake of weak disturbances. Colder valleys such as Cache Valley and the Uintah Basin are likely to see stronger inversions forming as snow remains on the valley floors, limiting the mixing influence of increasing solar radiation. Long term, a return to active weather will return for the end of the month which will likely mark the end to this winter's inversion season.

    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.