textproduct: Salt Lake City

KEY MESSAGES

- High elevation snowfall will bring travel impacts to elevations above 7500-8000 feet the remainder of the day and into Friday morning.

- An active weather pattern will follow this initial storm as we head into early next week, bringing continued threat for high elevation snowfall and travel impacts.

DISCUSSION

A weakly forced, but moist wave of energy continues to bring persistent high elevation snowfall across northern Utah this afternoon alongside valley rain and isolated to scattered showers across southern Utah. As we head through the evening hours, a much more robust shortwave trough will progress through Utah, providing much more ample lift across Utah and southwest Wyoming. This region of lift will pair with the abundant moisture in place to kick off a round of higher intensity snowfall in the mountainous terrain alongside continued persistent rain for the valleys. Alongside this more robust shortwave trough, cooler temperatures will be introduced to the region which will help to lower snow levels to around 7000ft by the morning hours on Friday.

As the shortwave trough pushes into the region this evening, a period of moderate intensity snowfall is expected for the high terrain across the state of Utah. With the core of the shortwave progressing through central and southern Utah alongside weak upper level support, thinking that there will be about a 6 to 9 hour period of higher intensity high elevation snowfall through southern Utah high elevations. A majority of impacts relating to snowfall are anticipated above about 9000ft, which targets the Brian Head/ Duck Creek area and the Tushar Mountains. Given the potential holiday traffic to local ski areas and impacts to travel at high elevations, have opted to issue a short-lived Winter Weather Advisory in the southern mountains. Additional Winter Weather Advisories have been issued for the central mountains and Wasatch Plateau with a similar concern of travel impacts for the higher elevation routes (SR-31 and US-40) as the more robust forcing moves into the area alongside cooler overhead temperatures. The previous Winter Weather Advisories for the northern Utah mountains remain in effect.

This shortwave trough will exit the region through the morning hours on Friday, allowing conditions to gradually stabilize across Utah and southwest Wyoming. That said, residual moisture in the lower levels alongside persistent northwesterly flow will aid in continued upslope snow showers across the northern Utah mountains through the early afternoon. Minimal impacts are expected during this time as precipitation rates are likely to subside as the best forcing moves eastward, however, lower density snowfall and cooler temperatures will make it easier for snowfall to stick to untreated roads/ concrete surfaces. In general, expecting conditions to largely subside by Friday evening and allow for dry conditions to return from late Friday through late Saturday.

From late Saturday/ Sunday forward, the upstream longwave trough pattern offshore of the U.S. west coast will begin progressing inland, likely ejecting a shortwave trough ahead of the feature before it moves inland. As such, active weather is likely (60-70% chance) to resume as we head into the beginning of next week, with high elevation snowfall and valley rain chances increasing overnight Saturday into Sunday as a shortwave progresses through the eastern Great Basin. The center of the aforementioned longwave is expected to dissolve and track into the southwest early in the week, helping to lower atmospheric heights and open the door to colder air and energy from the northwest.

There is fair agreement from ensemble guidance with regards to a broad longwave trough developing over the western U.S. through the latter half of next week which is reflected by overall cooler temperatures and modest precipitation chances through the second half of next week. While details of how individual impulses are uncertain at this time, there are several ensemble members from the GEFS and EPS that are supportive of snowfall in the lower elevation valley areas, especially across northern Utah/ southwest Wyoming.

AVIATION...KSLC

IFR conditions will continue at the SLC terminal through at least 00Z, with an extended period of MVFR conditions in rain continuing through at least 15-18Z Friday. Heavier precipitation will bring reductions in ceiling and visibility to the IFR range through 15Z.

REST OF UTAH AND SOUTHWEST WYOMING...Moderate to occasionally heavy precipitation will continue across most Utah and southwestern Wyoming terminals through the overnight hours. Conditions will quickly improve between 09-15Z across southern Utah, 15-18Z across northern Utah. Expect MVFR to occasionally IFR conditions in rain at most terminals, with rain mixing with snow at KEVW.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory until 11 AM MST Friday for UTZ110>112.

Winter Weather Advisory until 11 AM MST Friday for UTZ113-117.

Winter Weather Advisory until 5 AM MST Friday for UTZ125.

WY...None.