textproduct: Salt Lake City

KEY MESSAGES

- A splitting storm system will bring a potent cold front through much of Utah and southwest Wyoming through Thursday morning, dropping snow levels to most valley floors and bringing travel impacts, including during the Thursday morning commute.

- After a relative lull, a weaker system on the heels of the first will bring periods of snow showers to primarily the higher terrain of northern portions of the area Thursday afternoon through Friday. - Dry and increasingly mild conditions will return for the upcoming weekend, persisting into early next week.

DISCUSSION

A Pacific Northwest storm system has moved into the Great Basin this evening, with the associated cold front on the front edge of the system near a KTPH-KSLC line. Winds have been a bit gustier than expected along and just behind the front, with pockets of gusts in excess of 40 mph and isolated gusts over the GSL to around 60 mph. Believe that these winds will not last long enough to warrant a Wind Advisory, but have raised winds and wind gusts in the grids tonight and tomorrow based on current trends.

Seeing a band of precipitation, primarily snow, along the boundary that will march steadily east through the morning as the low makes its way into the state. The strength of the front might lead one to think that a more substantial storm is coming through. However, the low will be splitting as it tracks into the area, one piece ejecting north of the area and another ejecting south, and in its current state is not exactly moisture rich, bringing some limiting factors into play.

There is a high chance of a relative lull across the area mid to late morning, perhaps into the early afternoon. However, a weaker trailing wave behind the main system will act to increase instability over the area once again, bringing another round of snow. These showers will be more focused over the higher terrain, with northern and central Utah seeing the greatest impact. These showers are expected to continue into Friday morning, gradually dissipating during the afternoon and early evening.

Overall, both QPF and snow amounts have gone down just a bit with this evening forecast package, but the amounts still warrant the going Winter Weather Advisories for southwest Wyoming, the mountains of Utah, and some adjacent mountain valleys, and will make no changes to the headlines with this package. There is a high chance of many northern and western valleys seeing some light accumulations with the front tonight into the morning, and given the timing with the Thursday morning commute, this could bring some minor travel impacts. However, the threat does not look to be enough to require additional headlines. The potential for lake effect will be something to monitor going into Friday morning, primarily for areas south and southeast of the GSL, but chances of this happening have been trending downward, and this now looks like it has a 20-30 percent chance of happening.

Behind the exiting system, the Pacific ridge will build out eastward, a bit over the top of the lingering piece of the low over the Desert Southwest. This will bring dry and increasingly mild conditions through Monday, with maxes running at least 10-15F above normal by Monday afternoon. After that, guidance favors a more active storm track for the Pacific Northwest and areas closer to the Canadian border. Ensemble members, however, are trending away from solutions that would bring these systems far enough south to produce precipitation worth mentioning, but do bring some colder air into at least northern portions of the forecast area, bringing temperatures back closer to seasonal normals by the middle of next week.

REST OF UTAH AND SOUTHWEST WYOMING

A strong cold front will continue to cross the area tonight, with briefly strong gusts in excess of 40kt possible on the leading edge of the front. Precipitation will develop behind the front, briefly as rain in the lower valleys initially, otherwise snow is forecast at most locations across central and northern UT and southwest WY tonight and into the day on Thursday along with MVFR to IFR conditions. Conditions should rise to VFR by late Thursday morning at some locations as the front moves farther east and precipitation becomes more scattered.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory from 2 AM Thursday to 5 PM MST Friday for UTZ108-110>112-117.

Winter Weather Advisory from 5 AM Thursday to 5 PM MST Friday for UTZ113-118-119-125.

WY...Winter Weather Advisory from 2 AM Thursday to 5 PM MST Friday for WYZ021.