textproduct: Salt Lake City

KEY MESSAGES

- Much colder temperatures can be expected across the entire region with hard freeze conditions likely across most areas above 3,000 feet tonight and Friday night.

- A quick burst of snow will accompany a cold front as it continues to move through southern through east-central Utah tonight, with only minor accumulations expected. Additionally, there is a 30-40% chance for lake-effect snow showers south and southeast of the Great Salt Lake tonight into Friday morning.

- Strong northerly winds will occur overnight across lower Washington County in areas that are favored in northerly flow, such as the Black Ridge Canyon.

- High pressure will return by the weekend, bringing dry conditions with a steady warming trend.

DISCUSSION

An upper trough will continue to carve into Utah and western Nevada tonight. The associated cold front has already pushed south of a Cedar City to Hanksville line as of 04z and will continue through the rest of Utah over the next 2-3 hours. A relatively narrow band of precipitation continues near the cold front, where the thermal gradient is tight enough to allow for a brief burst of snow to the valley floors, especially in areas of heavier precipitation. As the duration of snow should be short, accumulations are expected to remain on the light side, with generally 1-2 inches of additional accumulation across the southern and central Utah mountains and less than 1 inch in the valleys above 4000-4500 feet. Localized minor impacts to travel will be possible on higher elevation roadways including I-15 summits across southern Utah tonight.

The precipitation associated with the frontal band will move out of the area early Friday morning. However, even behind the frontal band, isolated showers are expected to continue over portions of northern Utah tonight, as the associated trough continues to move into the area. Given warm temperatures over the GSL and continued cooling at H5 leading to a steepening of midlevel lapse rates, lake-induced CAPE in the 1000-1500 J/kg range would favor some showers off the GSL tonight into tomorrow morning assuming enough moisture remains in place. Local guidance suggests a 30-40% chance of lake-effect snow tonight, which would mainly affect the Oquirrh Mountains, the far eastern Tooele Valley, and far western SL Valley.

Isolated strong postfrontal wind gusts (50 mph or greater) have been noted behind the cold front, and this potential will continue, especially in favored downslope areas of eastern and southern Utah. Across lower Washington County, conditions are favorable for gap winds tonight, with gusts 50-55 mph possible through Black Ridge Canyon and downsloping off the Pine Valley and Beaver Dam Mountains tonight into tomorrow morning.

Otherwise, the other main impact will be the colder temperatures settling into the area behind the cold front. Overnight mins tonight and Friday night as well as afternoon maxes Friday will fall to around 10-15 degrees below climatology. This will result in widespread nighttime freezing temperatures across most of the forecast area except for the lower elevations of far southern Utah. In areas where the growing season has begun, freeze to hard freeze conditions will likely impact early-season agriculture as well as outdoor plumbing such as sprinklers.

As the trough moves out of the area, high pressure will build in for the weekend into the beginning of next week. This will bring mostly dry conditions along with a warming trend. Temperatures will quickly rebound to above normal by Sunday, as many valleys return to the 70s for highs. An active weather pattern looks to be in store for the middle to latter half of next week. While the consensus is for a mean trough across the Great Basin/Intermountain West (a general scenario depicted in all four ensemble clusters), the details as depicted in the global deterministic models, consisting of closed lows and various systems dumbbelling around each other, suggest that there is still quite a bit of uncertainty regarding specifics.

REST OF UTAH AND SOUTHWEST WYOMING

Showers associated with a departing frontal boundary will diminish overnight, though a low chance (~20-30%) of some lake effect snow showers is noted at terminals downwind of the Great Salt Lake and Utah Lake. These showers will bring potential for periods of reduced CIGS/VIS, though otherwise expect gradual clearing into Friday morning with mostly clear skies and a return to VFR conds at area terminals through the day. Northerly winds will tend to be favored at most area terminals behind the front, with gusty NE down-terrain winds particularly at SGU.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Warning until noon MDT Friday for UTZ102>106-114>116- 118>122-129-130.

Freeze Warning from 8 PM Friday to noon MDT Saturday for UTZ102>106-114>116-118>122-129-130.

Wind Advisory until 9 AM MDT Friday for UTZ123.

WY...None.