Inversion Forecast
Update 12/16/2024: Summary: Early week conditions feature a settling down of the recent active weather pattern as one final weak storm system translates through the region without much action. High pressure will begin building back into the West by midweek but a weak disturbance expected Wed/Thurs, will keep the greatest inversion impacts from being felt until Friday and through the weekend. The ridge of high pressure looks to hold onto its regional grip all the way to Christmas time when the next storm system might gather the right track to displace the ridge. Short-term (Dec 16 - Dec 18): Monday's active weather should taper off by Tuesday as regional high pressure builds back in across the West through Wednesday. The weather conditions will present weak inversions to begin to take hold, but impacts are not expected to be felt until the end of the week. Long-term: (Dec 19 - Dec 25): The focus of the inversion forecast attention turns to the end of week high pressure. The large pattern will manifest similarly to the early December inversion event, although the longevity of this round may fall short of the first major event of the year. Model consensus remains confident that the blocking pattern will set up through the days leading up to the Christmas stretch, with a robust storm system then forecast to sweep through. This far out, such expectations remain highly tempered, and if this robust storm system fails to materialize, the state could remain under the inversion-fueling high pressure through the remainder of the calendar 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.