textproduct: Salt Lake City

KEY MESSAGES

- High pressure continues to build over the region this weekend bringing mild and dry conditions.

- Winds become south-southwesterly Sunday ahead of a series of incoming systems bringing elevated winds and gusts to the area through much of the week.

- Multiple chances for accumulating mountain snowfall exist this week, with the Tuesday night through Thursday system bringing significant snowfall to the majority of our mountains.

- The threat for valley snow continues to increase with the Tuesday night through Thursday system for nearly all valley locations with the exception of lower Washington county.

DISCUSSION

Sunny and pleasant conditions persist today through Monday as ridging continues to build in, though this forecaster is sure that many are fed up with a relatively modest winter so far. However, these conditions are only temporary with quite an active pattern looking to develop next week. Until then, spring like conditions will yield temperatures around 10-15F above average for much of the area through Monday.

On Monday, south-southwesterly winds pick up across UT and SW WY ahead of our first incoming system as 700mb winds begin to strengthen and mix down to the surface. A longwave trough will progress inland across Southern CA, ejecting north and flattening somewhat as a second trough dives down from the PNW. Despite this, flow aloft isn't expected to weaken much Additionally, with increasing moisture and ascent through the day, most valley locations can expect to see rain develop in the late afternoon hours with high terrain across the state beginning to see the onset of snow. Snow will be contained to higher terrain as snow levels are generally expected to range between 6500-7500ft as this first system will be quite warm. With this storm, areas favored within a southwesterly flow regime will more than likely end up on the higher end range of the forecast, such as Brian Head and Provo Canyon.

Following the departure of the first wave, the aforementioned trough diving down from the PNW will impact the area bringing potentially more significant impacts to the forecast area starting Tuesday night. While ascent and moisture quality isn't forecast to be much different than the first wave, this system will arrive with much colder air aloft and quickly transition winds to northwesterly following its departure. With northwest winds and 700mb temperatures ranging from -14C to -17C on Thursday, this will give us our first real shot at accumulating valley snow across the Wasatch Front and most of our valley locations across the forecast area, except for lower Washington county, obviously. Some valleys have a higher chance of seeing more accumulations than others, such as the I-15 corridor running from Beaver to Cedar City which has a roughly 50- 70% chance of seeing 4" or greater Wednesday through Thursday. For comparison, most of the Wasatch Front has around a 20-40% chance for 4" or greater over the same time period, with benches having a higher probability. This is due to greater ascent further south lingering over southern UT, closer to the trough axis. Regardless, accumulating snowfall across the majority of our valleys appears increasingly likely with this setup and amounts may change as hi-res guidance begins to trickle in over the coming days.

Prolonged northwest winds will create an extremely favorable environment across most of our mountains for significant accumulating snowfall, with a strong emphasis on the Bear River Range and the Upper Cottonwoods. With this prolonged event running from Monday through Thursday and perhaps Friday, this appears to be the first event this season where we will refer to accumulations across most of our mountains in feet rather than inches. There does remain some uncertainty regarding if a brief lull occurs between the two waves which would impact totals somewhat, though this will not be too significant of a change given the favorable setup.

As we enter Friday, a couple lingering shortwaves may continue to progress into the forecast area bringing continued isolated snow showers to northern UT, albeit weaker as ascent continues to weaken with decreasing moisture quality. Ridging appears to build back in, though it remains uncertain with how long this will remain in place for. Looking into the long range, ensemble cluster analysis does indicate that the active period may continue with large scale western troughing as a common solution among most members.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will prevail across the area through the TAF period. Diurnally driven winds will continue through tonight, before gusty south winds develop after 16Z Sunday. With an increase in mid level cloud cover, the chance for MVFR VIS developing late tonight at northern terminals is less than 10%, and near 0% at southern Utah terminals.

SLC WATCHES/WARNINGS/ADVISORIES

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