Area Forecast Discussion

KEY MESSAGES

- Anomalous heat persists with daytime highs generally 10 to 20 degrees above normal through Tuesday.

- Strong southerly winds develop on Tuesday, particularly across the western valleys, with strong winds persisting across the eastern valleys on Wednesday. - An unsettled pattern develops by Wednesday as a trough and associated cold front move in with precipitation confined to northern Utah.

- Freezing temperatures will return to more rural valley locations Thursday through Saturday.

DISCUSSION

Unseasonably warm weather today and tomorrow with temperatures 10 (southern Utah) to 20 (northern Utah/SW Wyoming) degrees above normal is a result of a brief ridge building into the area. A closed low is currently moving widespread precipitation onshore to northern California. This low will continue to move inland and bring strong southerly winds ahead of a cold front that will usher in cooler and wetter weather into the area by midweek. This closed low will phase back into the northern jet as it pushes through our area which will keep the mean trough axis positioned to our northeast. This positioning will keep a cool and unsettled pattern persisting as we stay close enough to the trough axis to get skirted by shortwaves rotating around the periphery of the trough.

Deep southwesterly flow will increase ahead of a frontal passage associated with the aforementioned trough. Looking to our west across central Nevada winds are currently gusting in the 30s and low 40s. This will be similar to what our western valleys see tomorrow, with a 50-60% chance of seeing gusts up to 45 mph across the western valleys of Utah. As this trough moves through on Wednesday winds will gradually transition to more of a westerly component from west to east. This transition holds off until late Thursday for areas across eastern Utah so the southerly wind gusts will remain elevated across the eastern valleys on Wednesday, particularly for the Uinta Basin and Castle Country where there will be a medium (40%) chance of advisory level winds.

Precipitation will spread into northern Utah by midday on Wednesday as flow aloft transitions to westerly behind a cold front. Snow levels will quickly drop to 6000-7000 feet behind the front with rain across valley floors. This precipitation will generally be light and primarily from Utah county northward. The terrain that is favored in westerly flow could see some enhanced totals. QPF totals (25th-75th percentile) range from 0.25 inches to 0.75 inches across the northern valleys with 0.5 to 1.2 inches across the mountains with locally higher amounts across westerly facing aspects. The high terrain snow ratios will stay around 10:1 resulting in up to 6 inches of snow across most higher terrain with locally up to 10 inches across westerly flow favored locations.

In addition to the precipitation, a cooler airmass moves into the area dropping temperatures near to slightly below normal. Given the cooler airmass there will be freezing temperatures possible across some rural valley locations. There exists a low (<25% chance) chance across the central valleys Thursday and Friday morning, but cloud cover could limit the radiational cooling potential. Saturday morning has the greatest chance to see freezing conditions (50-60% chance) across most valley locations, outside of the Urban corridor, since clouds should be clearing more by then.

A closed low will move into the Mojave over the weekend and phase into the mean trough. This will bring more precipitation into the region with a focus of this round across central and southern Utah. 67% of ensemble members feature a shortwave moving into northern Utah and merging with this closed low by Sunday into Monday which would extend the precipitation chances spatially into northern Utah/SW Wyoming and temporally into Monday.

AVIATION...KSLC

VFR will continue with FEW to SCT high clouds. Winds will vary from SE to SW through the day today. No north winds expected today. Some gusts expected this afternoon, but only to about 18 kts. Light winds again overnight with another round of similar gusts tomorrow afternoon.

REST OF UTAH AND SOUTHWEST WYOMING

VFR will continue over the next 24 hours. Some mid to high cloud, but little aviation impact. Winds will be the main weather impact. Nothing to significant in speed (increase and decrease along the diurnal curve with some afternoon gusts to 20 kts possible), but shifting directions over the next day. Winds generally somewhere between a SW to SE over the next day with timings of when these shifts occur differing terminal to terminal. Consult individual TAF sites for site specific timing.

SLC WATCHES / WARNINGS / ADVISORIES

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