textproduct: Salt Lake City

KEY MESSAGES

- High pressure will keep inversions in place in prone valleys through at least late in the week. This will result in decreasing air quality and visibility with an increase in nocturnal fog for the valleys of northern Utah.

DISCUSSION

Strong high pressure remains centered over the west coast this afternoon, resulting in clear and dry conditions across Utah and southwest Wyoming. While higher elevation temperatures are quite mild, the valleys of northern Utah remain much colder, near seasonal normals, due to building inversions. This is also resulting in decreasing air quality and visibility. There is high confidence that this ridge will continue to build through the middle of the week, allowing particulates to continue to accumulate in the valleys prone to inversion conditions. Nocturnal fog which, so far, has been confined to the Bear Lake area, is likely to expand in coverage into the Cache Valley and portions of the Wasatch Front.

Guidance continues to indicate some cooling aloft Friday into Saturday as a broad trough dives south in the central United States. Ensemble guidance, which previously indicated the effects of this system would more likely than not be able to mix out the inversions, now only show a 30 percent chance of the system moving westward enough for this to happen. The more likely scenario is for the system to bring some modest weakening of the inversions, though they will remain in place. Thereafter, there is relatively high confidence that high pressure will rebuild, with the next chance of losing the valley inversions not expected until late next week.

REST OF UTAH AND SOUTHWEST WYOMING

The majority of the airspace will see VFR conditions through the evening with mostly clear skies. The exception to this will be in valleys prone to inversion conditions, where accumulation of particulates will result in low end VFR to high end MVFR visibilities through the overnight hours. Development of fog and stratus will result in IFR conditions in the Bear Lake area overnight, with a 30 percent chance of overnight fog reducing visibilities into the IFR/LIFR range in other areas seeing inversion conditions, including the Cache Valley and Wasatch Front.

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...None.