textproduct: Salt Lake City

KEY MESSAGES

- A cold storm system will bring showers to northern Utah through the overnight hours, with the associated strong front moving through northern portions of the area Thursday morning, and through southern Utah by Thursday afternoon. The system will bring significant accumulations to the northern Utah mountains, with some light valley accumulations likely by Friday morning.

- Widespread freezing temperatures will develop Friday morning, potentially damaging early season agriculture.

- High pressure will return for the weekend and early next week, bringing a drying and warming trend.

DISCUSSION

A cold trough is moving onshore along the Pacific Northwest this evening, with Utah and southwest Wyoming under an increasingly moist west to southwest flow out ahead of it. The break in the action from the previous trough was short lived, as a line of showers is tracking east across the Wasatch Front, with additional showers moving into the northwest desert. Periods of showers with snow levels around 8000 feet will continue through the overnight hours, with associated accumulations generally light.

The heaviest precipitation with the approaching system will come with its associated potent cold front. Latest guidance continues to indicate it will move through northern portions of the area Thursday morning, and through the Wasatch Front late morning through early afternoon. Snow levels will rapidly drop, reaching northern Utah valley floors, but associated accumulations that low will be light. Over the mountains, however, accumulations will be significant, with some locations seeing over a foot of snow. Going winter weather headlines cover this threat well. Limiting factor with the precipitation will primarily be the speed of the front, as the duration of the heaviest precipitation will only be a couple of hours or so. As the front tracks into central and southern Utah during the afternoon and early evening, it will still have a strong temperature gradient associated with it, but as it increasingly outruns its upper level support, associated coverage of precipitation with the front will decrease noticeably. Given the strong nature of the front, winds associated with the boundary will be occasionally strong and gusty. The greatest impact will be to portions of Castle Country prone to downsloping winds, where a Wind Advisory will be in effect tomorrow afternoon and evening.

As the trough continues across northern Utah Thursday night into Friday morning, instability showers will continue, primarily over the higher terrain of northern Utah, before tapering off by the afternoon. In the cold airmass behind the frontal boundary, all but the valleys of far southern Utah will see low temperatures near or below freezing, which could have some impacts for early season agriculture, as indicated by the going Freeze Watches. Low temperatures Saturday morning are anticipated to be just a couple of degrees less cold than Friday morning, but freezing conditions should still be fairly widespread.

Behind the exiting trough, there is high confidence that the Pacific ridge will rebuild back into the Intermountain West, bringing an end to the active pattern as of late and ushering in a warming and drying trend. After seeing highs near normal for this time of year on Saturday, maxes are expected to warm to around 10-15F above seasonal normals for early next week, a common theme this "cold" season.

REST OF UTAH AND SOUTHWEST WYOMING

Periodic showers can be expected across northern Utah and southwest Wyoming terminals through the night. Brief MVFR conditions and mountain top obscurations are possible in the stronger showers, otherwise VFR conditions will prevail. The showers may also bring briefly gusty and erratic winds, otherwise southerly winds will prevail into early Thursday morning. Southern Utah terminals will see VFR conditions under mostly clear to partly cloudy skies and southerly winds through Thursday morning. A strong cold front will cross northern Utah Thursday morning, then work its way into southern Utah by late afternoon or early evening. Strong gusty northwest winds can be expected along and behind the cold front. Periods of MVFR conditions with rain or a rain/snow mix (IFR in snow at KEVW) can be expected behind the cold front, especially northern terminals, with conditions gradually improving around 4-5 hours following the passage of the front.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Watch from Thursday evening through Friday morning for UTZ102>106-121.

Winter Weather Advisory from 3 AM Thursday to 9 AM MDT Friday for UTZ110>112.

Wind Advisory from noon to 9 PM MDT Thursday for UTZ120.

WY...None.