textproduct: Salt Lake City

KEY MESSAGES

- Dry conditions will give way to widespread valley rain and mountain snow late Friday into Saturday.

- Two more storms arrive next week with the first on Tuesday/Wednesday that looks very similar to the Saturday storm, and another towards the end of the week that has high-end scenario potential, but run-to-run consistency has been lacking.

DISCUSSION

A high-amplitude ridge has shifted east of Utah into Colorado this evening while upstream, a couple of storm systems are noted on water vapor satellite imagery. One is a closed low off the SoCal coast, while a second, larger, closed low is approaching the PacNW. The southern low will be coming onshore near the Cal/Baja coast by midday Friday. This system will gradually weaken as it becomes absorbed into the southerlies that will strengthen ahead of the second storm, which will continue to make its way onto the PacNW coast on Friday. The two storms will eventually phase into a negatively tilted trough which will then cross Utah Friday night through Saturday.

Given the increased southerly flow, some moisture will spread north into Utah on Friday ahead of the southern stream storm. As such, expect isolated to scattered showers to develop Friday afternoon into Friday evening. This will take place under a relatively mild airmass, with snow levels remaining mostly above 8500 ft during this timeframe. Precipitation will then become more widespread Friday night through Saturday morning ahead of and with a relatively fast-moving cold front. Snow levels will quickly fall to around 6-7 kft by around midday Saturday. However, precipitation will mostly wind down by late morning or midday Saturday behind the cold front, with the exception of the mountains, particularly those areas favored in northwesterly flow, which will maintain brief orographics into the afternoon. Additionally, with warm temperatures over the GSL, expect some showers to continue developing of the lake into the central Wasatch Front and adjacent mountains as well.

Most valleys are expected to see storm total precipitation amounts between 0.4-0.7 inches near the I-15 corridor and less elsewhere. Meanwhile, mountains are expected to see 0.6-1.2 inches with locally higher amounts in the upper Cottonwoods and near Brian Head. Snow amounts remain generally in the 4-8 inch range, mainly above 7500 feet, with higher amounts possible in the upper Cottonwoods, Tushars, and near Brian Head.

A transient ridge will cross the area late Saturday through Monday, bringing a break in the weather. However, the pattern remains progressive, with the next storm system looking to impact the area during the Monday night through Tuesday night timeframe. This will be another relatively fast-moving system which will also bring widespread precipitation to the area. However, it looks like this could be a colder system, which will result in lower snow levels, potentially down to at least 5000 feet.

After a brief break Wednesday into Wednesday night, yet another storm system could impact the area by Thursday morning. There is good agreement in the large-scale pattern regarding the existence of this late week storm, but with uncertainties in the timing and evolution. Latest global deterministics are leaning towards this storm being a broad closed low which will slowly move through the region through the weekend, bringing an extended period of precipitation to the forecast area.

AVIATION

KSLC...Partly cloudy skies with VFR conditions prevailing into early Friday with diurnally-driven southeasterly flow. As high pressure shifts east of the area, cloud cover gradually increases although VFR conditions are expected to prevail. Southerly winds are expected to persist through Friday, with some modest gusts up to around 25 kts. There is a 10-20% chance of an isolated light shower after 21Z Friday, with higher chances later in the forecast period.

REST OF UTAH AND SOUTHWEST WYOMING...Area terminals expected to see partly cloudy skies with diurnally normal to light variable winds into early Friday. High pressure will begin to shift east of the area, allowing VFR cloud cover to increase throughout the day. Southerly winds will also increase, especially after sunrise, with many terminals (especially exposed ones) seeing modest gusts develop by late morning into the afternoon. There is a chance of some isolated light shower later in the period, especially at the southern terminals (KCDC and KSGU).

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...None.