textproduct: Salt Lake City

KEY MESSAGES

- Northern valley inversions will remain in place through Friday. Haze, decreased air quality and areas of fog will continue.

- Approximately 60% of ensemble members bring sufficient mid- level cooling to at least partially ventilate the northern valleys Friday evening into Saturday morning.

- North to northwest flow will remain across the region through at least mid-week.

DISCUSSION

Looking at both air quality sensors and the trend in the KSLC sounding, inversion conditions eased slightly with the passage of a shortwave trough and modest mid-level cold air advection Thursday. As an upper level trough shifts into the Plains today, expect mid-level cooling to continue. The HREF is bullish, with the mean 700mb temperature near -6C across northern Utah. The LREF conditions to suggest around 65% of members with sufficient mid-level cooling to continue the trend of weaker inversion conditions this afternoon and evening.

With how fine of a line it is between mixing out inversions and just ventilating valleys to a degree, it is hard to know at this time if portions of the Wasatch Front will improve significantly if some of the colder ensemble members come to fruition. Most probable forecast is there will be a degree of weakening of the inversion and thus an improvement in visibility in general due to haze. That said, having trouble seeing blue bird conditions by Saturday across the Wasatch Front/northern valleys. Will need to keep an eye on aircraft soundings through the day to see how cold mid-level temperatures shift...and whether this is enough to dislodge the inversion.

With north to northwest flow continuing across northern Utah through at least midweek, it is unlikely the inversion will become as strong as this past Wednesday. Some of this will hinge on what happens in the next 24-36 hours...and what the particulate concentrations are by Sunday morning.

As always, for air quality forecasts and observational data, please see air.utah.gov for the latest information. Current forecast as of 2 AM is for Davis, Salt Lake and Utah County to remain at orange/unhealthy for sensitive groups through Saturday

The next real threat of any measurable precipitation looks to hold off until early Friday across northern Utah...but given this is a week out, something to monitor.

REST OF UTAH AND SOUTHWEST WYOMING

Localized shallow fog is expected for areas of northern Utah near the Great Salt Lake, Utah Lake, and Cache Valley through around 17-18Z. Valley haze on the Wasatch Front is expected to be more diluted today, but VIS may only improve to around 6SM with more significant slantwise reduction expected around sunrise and sunset. Winds will be generally light and terrain driven across the area throughout the day.

SLC WATCHES/WARNINGS/ADVISORIES

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