National Weather Service United States Department of Commerce

The Weather Hazard Threefold

A large dome of high pressure will continue the sweltering heat in parts of the West and the central Plains. Meanwhile, a cold front will produce severe thunderstorms, capable of all hazards, the next few days from the Mid-Upper Mississippi Valley into the Ohio Valley and Great Lakes. Finally, Potential Tropical Cyclone Three will bring heavy rain and flooding to the northern Gulf Coast. Read More >



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The Clearing Index is an Air Quality/Smoke Dispersal Index used to regulate open burning and as input for other air quality decisions throughout Utah. The Clearing Index is defined as the Mixing Depth (depth of the mixed layer in 100s of feet above ground level) multiplied by the Transport Wind (average wind in the mixed layer in knots). Clearing Index values below 500 are considered poor ventilation and open burning is restricted under these conditions. Any Clearing Index values above 1000 are considered excellent ventilation and are referred to as 1000+. Data for the Clearing Index on these web pages are derived from several operational atmospheric computer models. The data will be reviewed and may be edited by NWS meteorologists before dissemination.
An example calculation of the Clearing Index:
Mixed Layer Depth = 10000 feet
Transport Wind = 8 knots
Clearing index = (10000/100 feet) X 8 knots = 800
Note: Clearing Index is 1000+ if measurable precipitation or cold front passage occurs.
Utah Smoke Management Program