textproduct: Salt Lake City

DISCUSSION

Broad upper level ridging will continue to build across the Desert Southwest through Wednesday. As southwest flow increases ahead of a Pacific trough Wednesday, precipitable water values at or above the 90th percentile will shift into southern Utah early Wednesday, reaching northern Utah by Wednesday afternoon. This will combine with a shortwave trough rotating around the periphery of the ridge to bring sufficient forcing for convection.

Model soundings suggest that this moisture advection will be mainly in the mid-levels, with a relatively dry sub-cloud layer. HREF mean SBCAPE values look to be around 350-600 J/kg, with deep layer shear at or above 20kts. Stronger storms may be capable of brief periods of heavy rain along with microburst winds in excess of 50 mph. The threat has shifted in the latest guidance to much of the state rather than just southern Utah.

Convection may be limited to the far eastern portion of the CWA Thursday afternoon and evening as the best forcing shifts east of the region. Something to monitor moving forward given the near record to record dry fuels across the state. A reminder to please use Fire Sense and avoid additional human-caused starts in these conditions. This means paying attention to fire bans, dousing your campfires, checking for heat, and then dousing again until there's no heat, avoid dragging chains, parking on grass, consider skipping fireworks this year and leaving it to the professionals, etc.

After the lightning will come what is looking like a period of significant fire weather conditions Friday into the weekend. Very strong southwest winds with gusts approaching 50 mph, combined with very low humidities will bring widespread critical fire weather conditions to the region. See the fire weather discussion for more information.

AVIATION

KSLC...Generally light southeasterly or occasionally variable winds will persist through the night into Tuesday morning, becoming northwest after 18-19z. VFR conditions will likely prevail, though wildfire smoke could produce reductions in slantwise visibility, particularly around sunrise and sunset.

REST OF UTAH AND SOUTHWEST WYOMING...Winds will be largely light and terrain-driven across the area tonight, but may become a bit squirrelly near KLGU overnight as a few light high-based showers move through between ~10-15z. Tuesday afternoon, west to southwest winds will increase across southern Utah, with local gusts in excess of 25kt. VFR conditions will prevail across most areas, though wildfire smoke may result in slantwise VIS reductions across Utah and southwest Wyoming...particularly sites closer to wildfires such as KPVU and KHCR, and around sunrise/sunset.

FIRE WEATHER

A hot and dry airmass will remain in place across the state through Tuesday, as daytime temperatures continue to run 5 to 10 degrees above normal for the latter half of June. Afternoon RH will remain below 15 percent across nearly all elevations below 8000 feet through Tuesday, with overnight recovery marginal to poor in the north, and nearly non-existant across much of southern Utah. Gusty west winds will trend a little stronger Tuesday across south central and southeast Utah, which prompted the issuance of a Red Flag Warning for zones 493, 494, 496 and 498.

Moisture will spread northward into southern, central and potentially portions of northern Utah Wednesday, bringing a chance for showers and thunderstorms. Initially these storms will likely be high based with dry lightning and strong outflows a threat. However, a quick transition from dry to a mixture of wet and dry storms may occur Wednesday afternoon/evening, particularly across southern Utah. Given this uncertainty have held off on a Fire Weather Watch at this time. This moisture looks to be swept out of the area during the day Thursday, as a general southwesterly flow develops across the region.

A potentially significant period of critical fire weather conditions is looking more likely Friday into Saturday, as strong southwesterly flow along with a very dry airmass spread across the state, ahead of an approaching cold front. Wind gusts Friday look likely to reach the 40 mph range across western Utah. As the front approaches, and eventually crosses Utah Saturday, these wind gusts may reach 50 mph at times across central and southern Utah Saturday afternoon. There is some uncertainty with frontal timing which will determine how far north these strong winds extend Saturday, but look most likely south of the I-70/US-50 corridor. As this front sweeps through the region, much cooler temperatures will follow for Sunday.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Red Flag Warning from noon to 10 PM MDT Tuesday for UTZ493-494- 496-498.

WY...None.