textproduct: Salt Lake City

KEY MESSAGES

- Areas of critical fire weather conditions will return to portions of southern Utah through Sunday afternoon.

- A quite unseasonably cold storm system will result in temperatures 10-20F below normal for Sunday and Monday along with accumulating mountain and mountain valley snow, significant for the Western Uinta mountains and in southwest Wyoming. - Freeze conditions will impact many Utah valleys outside of the Wasatch Front Monday and Tuesday mornings. Some areas that might see a hard freeze include the Cache Valley, Wasatch Back, west central Utah, southwest Utah, and the Sanpete Valley.

DISCUSSION

A broad, cold storm system has moved onshore along the Pacific northwest coast this morning, with an ejecting wave from the system currently moving over Nevada. Ahead of the ejecting wave, clouds are increasing over Utah and southwest Wyoming, primarily along and behind a weak frontal boundary situated near a KTPH-KEVW line. Some weak echoes have developed on radar in the vicinity of the boundary, though little precipitation looks to be hitting the ground at this time. Temperatures will stay mild, up to 10F above seasonal normals, for areas ahead of the front, with areas behind the front cooling to near seasonal normals.

The boundary will track slowly south during the day, acting as a focus for some more substantial convection, scattered in nature, this afternoon and evening. Lower levels remain very dry, so gusty and erratic winds will be the primary threat with any storms that develop, with the focus over central Utah. Synoptic winds will also be on the breezy side today, particularly ahead of the boundary. Relative humidities remain quite low for southern Utah, so this will bring areas of critical fire weather conditions. See the fire weather section of the AFD for more details.

The main Pacific Northwest trough is expected to phase with the initial wave overnight as it begins its dive southeast, crossing the forecast area Sunday afternoon through Monday. This system will bring a much more potent front along with it, resulting in high temperatures up to 20F below seasonal normals for both Sunday and Monday across the area, temperatures more typical of early March. It also possesses a good amount of moisture and instability, so it is set to bring accumulating snow to all the mountains of Utah and with snow levels bottoming out around 5000-6000 feet Monday morning, likely to the mountain valleys as well. Guidance has been consistent in showing a high chance of significant accumulations for the western Uinta Mountains and southwest Wyoming, so have issued a Winter Weather Advisory for those areas with this package. Forecast snow numbers have overall come up in this package compared to previous forecasts, and now put the central and southern mountain forecast totals marginally into the advisory range. Given more uncertainty here and the later onset of precipitation for those areas, have opted to go without headlines in those locations at this time.

With the quite unseasonably cold airmass in the wake of the trough, freezing overnight lows look to become widespread for most valleys of Utah (excluding the Wasatch Front and far southern Utah) with a good chance of a hard freeze for many outlying valleys, particularly Tuesday morning with less cloud cover expected. This will bring impacts to agricultural operations and will impact other sensitive vegetation as well.

There is good agreement that the main trough will move east of the forecast area Monday evening, though one last weak trailing wave will follow for Monday night into Tuesday, allowing the threat of precipitation to linger, especially for northeastern portions of the forecast area. After that, the strong ridge off the Pacific coast is expected to build eastward, bringing a warming trend back to the area. This morning's guidance increasingly favors a solution that would slide a weakening trough over the ridge and across the forecast area Wednesday night into Thursday. Associated moisture and instability looks unimpressive, but this solution would slow down the warming trend, delaying the onset of above climo high temperatures until Friday, leading into a very warm upcoming weekend.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions are expected across the area with high-based showers and thunderstorms forming through the late morning and afternoon hours. Gusty and erratic outflow winds will be possible near showers and thunderstorms. Breezy west to southwest winds are expected across the southern and eastern half of the area through the day today, with the northern and western portions of the area expected to see breezy northwesterly winds. A frontal boundary will move from north to south through the evening hours, moving along the Wasatch Front from 01-05Z and bringing an increase in northerly wind gusts to around 30- 35kts. This boundary will continue southward through the morning hours, becoming more diffuse as it reaches KCDC.

FIRE WEATHER

An initial weak cold front has moved into central Utah. Winds ahead of the front will becoming increasingly breezy as relatively humidity values remain very low, so southern Utah will see areas of critical fire weather conditions and a Red Flag Warning is in effect. Scattered showers and a few high based storms will develop this afternoon, primarily along the frontal boundary. Any storms that develop will be capable of producing gusty and erratic winds as well as isolated dry lightning. The main storm system will cross the area Sunday afternoon through Monday, bringing much colder temperatures, and accumulating snow to the higher terrain of Utah. Winds will remain elevated over southern Utah, and while relative humidities will be increasing, they will remain critically low over far southern Utah, where a Red Flag Warning will remain in effect tomorrow. Behind the exiting system, conditions will trend drier and warmer for the remainder of the upcoming week.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory from noon Sunday to 6 PM MDT Saturday for UTZ112.

Red Flag Warning until 9 PM MDT this evening for UTZ489-494-495.

Red Flag Warning until 9 PM MDT Sunday for UTZ497-498.

WY...Winter Weather Advisory from noon Sunday to 6 PM MDT Saturday for WYZ021.