textproduct: Salt Lake City

KEY MESSAGES

- Record warm temperatures will likely continue through Thursday.

- Wind advisories for western and portions of southwestern Utah Wednesday afternoon through Friday for gusts up to 50 mph.

- 6 to 12 inches of snow is expected across the southern mountains and western Uinta Mountains above 9000 feet Wednesday into late Thursday.

- Moderate to heavy rain will occur across southern Utah below 8500 feet Wednesday into Thursday. Expect enhanced runoff across this area, with all streams, slot canyons, and other waterways running high.

- A cold front Friday evening will help to lower snow levels, with a slight (25%) chance of snow falling to valley floors by Saturday morning.

DISCUSSION

Record warm temperatures continue across most of the western CONUS, including Utah. Both record warm daytime highs and nighttime lows have been set multiple times over the past week. This trend will likely continue through the end of the week as warm southerly flow will persist ahead of a storm that is expected to arrive Wednesday. This first storm will be warm and wet with very high snow levels. A cold front will arrive late Friday that will help drag snow levels down significantly. Then we begin to dry things out by Sunday with dry conditions remaining along with temperatures starting to creep back up through the middle of next week.

Strong southerly winds have aided in the record warm high and low temperatures across the area. These southerly winds will increase in magnitude, particularly across the western and southwestern portions of Utah, on Wednesday and persist through Friday. This has prompted the issuance of wind advisories for these areas for wind gusts up to 50 mph with isolated gusts to 60 mph across areas that are prone to southerly downsloping winds.

A landfalling atmospheric river will advect moisture into the Great Basin on Christmas Eve and Christmas Day resulting in widespread rainfall across portions of the area. Areas that do well in southerly upslope flow will see enhanced QPF totals, such as Zion and the southern facing aspects of the Pine Valley mountains. Given the prolonged duration and heavy precipitation rates, expect rivers, creeks, streams, normally dry washes, and slot canyons to have higher than normal flows across much of southwestern Utah.

Given the strong southerly winds that will be in tandem with the moisture, some areas that don't do well in southerly flow, such as Cedar City and much of the Wasatch Front may not see much in the way of moisture with this Christmas storm as downsloping will prevent a lot of moisture from making it to the surface. Additionally, snow levels will be very high for this time of year. Throughout the duration of the storm snow levels will range between 8,500 feet to 10,000 feet. This will confine most of the snow accumulations to areas above 9,000 feet with the best accumulations above 10,000 feet. Therefore, substantial snow accumulations will be confined to the Uintas and the southern mountains with this first round of moisture.

A second round of precipitation will accompany a cold front late Friday into Saturday. This round will have much colder air aloft (H7 ~-6 to -10C) behind the cold front that will help to bring snow levels much lower, and in some areas snow levels may approach valley floors. Additionally, northwesterly flow behind the front will help to aid in more snow across areas that do well in this flow regime, such as the Upper Cottonwood Canyons.

The airmass behind this front will bring temperatures back to near normal for this time of year, but those will be short-lived as ridging starts to build back in from the west. This will keep conditions mostly dry Sunday through the middle of next week with temperatures rebounding back above normal.

REST OF UTAH AND SOUTHWEST WYOMING

Winds at northern terminals will diminish this evening, with a 30% chance of becoming gusty south in the SL valley after 03z. Southern terminals will see vicinity showers increasing after 00z, with continued elevated winds likely at CDC. These showers may bring lower CIGs around 3000ft to KCDC and KSGU, and may briefly enhance southerly wind gusts (10% chance of exceeding 40kts).

SLC WATCHES/WARNINGS/ADVISORIES

UT...Wind Advisory from 11 AM Wednesday to 5 PM MST Friday for UTZ101- 102-115-122.

Winter Weather Advisory from 11 AM Wednesday to 11 PM MST Thursday for UTZ112.

Winter Weather Advisory from 5 AM Wednesday to 11 PM MST Thursday for UTZ125.

WY...None.