textproduct: Salt Lake City

KEY MESSAGES

- Wind gusts in excess of 45 mph are expected across southwest to west central Utah, southern to central Utah valleys, and the Tooele Valley ahead of an approaching cold front Sunday afternoon/evening.

- A system will bring unsettled conditions with periods of valley rain and accumulating mountain snow Sunday through Tuesday.

- Freezing conditions appear likely in many areas including the Wasatch Front and many Utah valleys (outside Lower Washington County) Thursday and Friday night as a colder system moves through roughly Thursday through Saturday.

DISCUSSION

A robust shortwave impulse which pivoted through the region Saturday is continuing to eject northeastward this evening, after resulting in an active day with numerous strong to severe wind reports and small hail. Utah and southwest Wyoming are now entering something of a dry slot in advance of a broader and deeper trough slowly churning inland from the California. As such, while some cloud cover will linger, precipitation chances will remain low until around Sunday afternoon when the aforementioned system begins to exert more influence. While a few degrees cooler than last night, overnight temperatures will remain well above seasonal normal, especially where clouds linger or more breezy conditions are maintained.

Deep southwesterly flow will become further enhanced as the broad trough continues shifting into the Great Basin, with a belt of 700 mb winds increasing overhead to around 40-55 kts. In turn, increasing mixing from mid morning on through the afternoon will bring this higher momentum air downward, resulting in gusty conditions more or less areawide. The highest threat of wind gusts in excess of 45 mph is currently noted across southwest to west central Utah, southern to central Utah valleys, and the Tooele Valley. A Wind Advisory is in effect Sunday afternoon and evening accordingly. That said, further expansion of the advisory area may be warranted, and even if not quite hitting criteria, most lower elevation locations will see frequent gusts in the 30-45 mph range. Higher elevations, especially near higher ridgetops will see stronger gusts. In addition for potential to blow around loose and unsecured objects, these strong winds may bring crosswind impacts to motorists (especially in high profile vehicles) on east-west routes, as well as periods of reduced visibility due to blowing dust. Winds and gusts will finally begin to decrease following the passage of a cold front late Sunday afternoon into Sunday evening.

Instability will begin to increase Saturday afternoon, allowing for the development of scattered prefrontal showers and thunderstorms. Given the strong flow overhead, this precipitation will also carry the risk for some strong and gusty winds in addition to the ongoing breezy conditions. The cold front will gradually push eastward through Utah late Sunday afternoon on into the evening. Models do not suggest strong organization along the boundary, but do anticipate coverage of scattered showers and thunderstorms to increase along the front. Periods of valley rain showers and accumulating mountain snow will then persist into Tuesday with some ebb and flow in coverage/rates as a result of embedded shortwave impulses within the broader trough as it shifts through. The downward trend in overall water amounts has not substantially reversed, so mountain snow accumulations remain fairly modest. In general, still looking at around 2-5" at most Utah mountains, and locally 6-12" or so at favored areas such as the Upper Cottonwoods or Tushar Mountains. Given the longer duration and somewhat sporadic nature of the system, have held off on any winter weather headlines. Still, motorists traveling over high elevation passes or to those locally favored areas should at least be prepared and aware of potential for winter driving conditions. In terms of snow levels, anticipate initial levels around 7500-8000 ft gradually dropping nearer to 6000-6500 ft by Monday morning.

With the cool nature of the system, temperatures will also drop across the forecast region into early next week. After a period of anomalous heat, afternoon highs will actually fall back to around 5-10 degrees below seasonal normal. Overnight lows will also dip, with forecast lows suggesting potential to bring some locally freezing temperatures to some central and northern Utah valleys Tuesday night into Wednesday morning. For those with gardens or other sensitive agriculture, will want to keep an eye on any trends to exact numbers.

After a brief period of ridging in the middle of the week, and a slight corresponding warmup, models are continuing to show consistency in another trough deepening through the Great Basin and Intermountain West sometime Thursday into the weekend. Still a bit of uncertainty being a bit out in time, but models do show decent agreement in this being a colder system as well. Current ensemble 75th-25th percentile 700 mb temps fall to around -9C to roughly -12C, which would be on the colder side for a mid April storm. As currently progged, it would be cold enough for maybe some valley flakes in northern Utah, light snow accumulations across portions of the Wasatch back, and some modest mountain snowaccumulations. For lower elevations, the cold temperatures and potential for freezing conditions Thursday night into Friday morning and Friday night into Saturday morning would likely prove more impactful, particularly to those with sensitive vegetation. As has been the case with most systems this season though, will need to keep an eye on trends to see if it starts to show signs of moderating the other way.

REST OF UTAH AND SOUTHWEST WYOMING

While many sites will experience fairly light winds overnight, southerly flow will begin to increase after 09z, particularly at sites downwind of higher terrain. Southwesterly winds will further increase after 16-17z, with gusts to 35-45kts across much of the area. Blowing dust is possible in prone areas in western UT, reducing VIS to MVFR at times. Although a few isolated showers/thunderstorms may develop over higher terrain after 18z, higher coverage showers will arrive along a cold front that is expected to push into northwestern UT after 20z.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Wind Advisory from 10 AM to 8 PM MDT Sunday for UTZ102-115-116- 118>120-122-126>128.

WY...None.