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    Inversion Forecast

    Notice: Due to the federal shutdown, data feeds critical to the graphical inversion forecast product are offline. Please refer to the following discussion for guidance on the inversions forecast until further notice.


    Discussion Last Updated: 01-08-2019 2:27:13 pm MST

    Update 01/08/2019: Intermittent active weather continues throughout the extended forecast helping to minimize the strength of valley inversions as well as the persistence of pollution-trapping conditions. Inversions are expected to make a brief return this week, although the relatively warm air in place over the state should help to mitigate the magnitude of impacts. Over the next two-three weeks, inversions will develop at times, although not with any particular significance but expect these events to drive marginally poor air quality. With a continuation of the active weather pattern, these inversion periods should remain present at best for a few days. Considering the typical January weather, our extended outlook this year remains positive! Happy New Year.

    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.