textproduct: Salt Lake City

KEY MESSAGES

- Strong Washington County gap winds will continue through Sunrise, with gusts to 60 mph impacting the I-15 corridor through Black Ridge Canyon including adjacent areas near Toquerville, La Verkin and portions of Hurricane. There is a 20% chance wind gusts will exceed 65 mph in these area. Winds will decrease after 8-9 AM this morning.

- A lake effect snow band will continue to affect far western Salt Lake Valley, eastern Tooele Valley, and northwest Utah County near Eagle Mountain. An additional 1 to 3 inches of snow is possible in these areas before this band dissipates by mid morning.

- Freezing fog will be possible across the Cache Valley through this morning.

- A potentially prolonged inversion cycle will set up this weekend across northern and central Utah, and persist through most of next week. This will result in an increase in urban haze, nocturnal fog, and degrading air quality across prone valleys including the Wasatch Front.

DISCUSSION

The upper trough which passed through the region Thursday is gradually making its way through the central and southern Rockies early this morning, leaving a cold northerly flow in its wake across the forecast area. Within this flow, shortwave ridging is currently building across the eastern Great Basin, resulting in increasing subsidence across northern Utah. As this continues over the next few hours, the lingering lake band emanating off the GSL should continue to weaken and likely dissipate by sunrise. Extended the going Winter Wx Advisory for areas south of the lake, but once this band winds down should be able to drop this headline.

Elsewhere, stratus remains in place along northern/western slopes of the higher terrain across northern and central Utah. This stratus extends upstream into some valley locations such as the Cache, and has thus far deterred fog formation, however the potential remains for quick fog development if skies clear, and will hold onto the Freezing Fog Advisory for the Cache Valley for the time being. Meanwhile, a tight pressure gradient in the wake of the departing system is maintaining strong gap winds across favored areas of Washington County. Thus far peak gusts have reached the low-mid 50 mph range, and these winds will persist for a few more hours before the gradient weakens this morning.

With this cold northerly flow in place (-15C airmass at 700mb per RAP analysis), max temps today will struggle to reach the freezing mark across western valleys including the Wasatch Front, while lower elevations of southern Utah will reach the low 40s. Clear skies tonight will allow temps to fall into the teens, with single digits in sheltered locations such as the Cache and Bear River Valleys.

Beyond tonight, we transition into a potentially prolonged inversion cycle for most northern and central valleys. A dominant mid level ridge will begin spreading into the forecast area tonight, with longwave ridging remaining in place across the region through most if not all of next week. With warming aloft overnight, valley inversions will quickly develop Saturday as the cold airmass currently in place across the region becomes trapped within most northern and central Utah basins including the Wasatch Front. As such expect an increase in urban haze by Monday (if not over the weekend), along with overnight fog and stratus becoming increasingly common by early next week. Undercut guidance through much of next week to reflect a more stagnant trend in temperatures across the northern valleys. Late next week would bring the first chance for dislodging these stagnant airmasses resulting from a backdoor front associated with a potential trough digging through the Rockies, however confidence is pretty low at this point in this scenario.

REST OF UTAH AND SOUTHWEST WYOMING

Winds will prevail from the northwest and be relatively light. The main exceptions will be at KPVU and KSGU, where downslope flow from the north will enhance winds. Locally stronger gusts around 30 knots at those locations will continue through roughly 00Z. Broken to overcast clouds in VFR range for southwest Wyoming and northern Utah will become more scattered, with mostly clear conditions by 21Z.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory until 8 AM MST this morning for UTZ102- 105-106.

Freezing Fog Advisory until 9 AM MST this morning for UTZ107.

High Wind Warning until 8 AM MST this morning for UTZ123.

WY...None.