textproduct: Salt Lake City

KEY MESSAGES

- Two storm systems will impact Utah Tuesday through Friday, though uncertainty in snow amounts is still high with each one. The first will be relatively warm, bringing valley rain and mountain snow to much of the area.

- A colder, likely stronger system will bring widespread mountain snow and even a chance for light valley snow by Friday morning, particularly across northern Utah/southwest Wyoming.

- Early season agriculture will likely be impacted by freezing temperatures and frost on Friday and Saturday mornings.

DISCUSSION

A broad but very low amplitude ridge remains in place over the Intermountain West this evening, with Utah under a warm west-southwesterly flow aloft. Monday will be fairly similar, although max temperatures are expected to be around 1-4 degrees cooler, this as clouds increase and heights fall. Additionally, a low-amplitude trough will cross the PacNW and Montana along the Canadian border on Monday. This will push a weak cold front into northern Utah Monday evening. Models are trending slightly farther north with this trough, and as a result, the front itself looks to weaken and stall not much farther south than I-80. Although temperatures will cool for Tuesday, afternoon maxes are expected to remain generally 3-8 degrees above climatological normals.

Precipitation associated with this front is also expected to be fairly limited. Some weak showers are expected to develop across central Utah Monday afternoon ahead of the boundary, strengthening a bit as low-level convergence increases in the evening. Showers are expected to increase near and north of the stalled boundary Tuesday afternoon, then become more widespread across the forecast area by Tuesday evening as the next shortwave trough approaches the area. This trough will cross Utah Tuesday night into Wednesday morning and will be accompanied by increased moisture transport, which will allow for widespread measurable precipitation. Between Tuesday evening through Wednesday morning, most mountains have a 40% to a greater than 65% chance of seeing over 0.75 inches of precipitation, while many valleys except the drier eastern valleys have a 30% to a greater than 60% chance of seeing over 0.5 inches of precipitation, highest along the Wasatch Front. With the airmass trending cooler, snow levels are expected to fall to 7.5-8kft. This will bring accumulating snow to the high elevations, although low snow ratios will largely limit accumulations to below advisory criteria.

After a brief lull in precipitation late Wednesday into early Thursday, the advertised colder and stronger trough will then impact the area, pushing a cold front into northern Utah beginning Thursday morning. Gusty southwest winds can be expected across southern Utah Thursday afternoon ahead of the front before it moves through that area Thursday evening. Model consensus continues to bring H7 temperatures down to -10C or colder across at least the northern half of Utah Thursday night into Friday, which would be cold enough to drop snow levels to the valley floors. While the relatively fast-moving nature of the frontal band will likely limit snowfall across the valleys and the mountains of central and southern Utah, favorable orographics and relatively steep lapse rates could maintain snow showers across the northern mountains into Friday. The NBM currently has a greater than 85% chance of 6 inches of snow or greater in the upper Cottonwoods and a greater than 65% chance across the rest of the northern Utah mountains.

Behind the cold front, temperatures are likely to fall below climatological normals across northern Utah on Thursday and in all areas by Friday, this after our long stretch of abnormally and record warm temperatures. Additionally, many valleys, especially those in outlying areas, are likely to see freezing temperatures Friday morning and Saturday morning, which would affect any early season agriculture. Temperatures will then gradually trend warmer again through next weekend, accompanied by fairly benign weather, as high pressure builds back into the area.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will prevail through the TAF period. Winds will generally remain terrain driven through midday Monday. By Monday afternoon winds will have a light northerly component across northern TAF sites, while southwesterly winds prevail across southern Utah.

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...Red Flag Warning until 9 PM MDT Monday for WYZ277.