textproduct: Salt Lake City

KEY MESSAGES

- Gusty winds will develop over portions of western Utah Tuesday, strongest over west central and southwest Utah, where gusts to 50 mph can be expected. Gusty and erratic winds could also develop with showers and thunderstorms tomorrow, with the best coverage over the higher terrain east of I-15.

- Gusty winds will become more widespread over central and southern Utah on Wednesday, bringing the potential for critical fire weather conditions where fuels are dry. The threat of critical fire weather conditions will continue into Thursday for the valleys of eastern Utah.

- The trough over the Great Basin will cross Utah and southwest Wyoming late Thursday into Friday bringing a return of scattered showers and thunderstorms to northern Utah and bringing temperatures back down to near seasonal normals across the area.

DISCUSSION

Utah and southwest Wyoming are under a southerly flow this evening on the back side of a ridge moving into the central United States. In this flow, moisture and instability continue to be drawn northward, which is allowing some showers and thunderstorms to continue, primarily for areas east of I-15. With waves continuing to filter north tonight into tomorrow morning, some convection will continue through the overnight hours.

A trough currently over the Pacific Northwest will drop into the Great Basin by Thursday afternoon. Initially, the associated moisture and instability will remain west of the area. However, the resultant increase in the pressure gradient will result in some strong, gusty winds over portions of western Utah. Have added a Wind Advisory for southwest Utah in this package to accompany the one already issued for western Millard and Juab counties, as the strongest winds will be concentrated in this area, where latest guidance indicates a 50-70% chance of wind gusts to 50 mph. Weighed adding the west desert at this time, but while it would not be surprising to see isolated gusts in excess of 40 mph, think these winds will not have the duration to warrant headlines.

As the broad low wobbles eastward, the extent of the gusty winds will spread eastward across central and southern Utah. Gusts overall will be less strong than those expected Tuesday for western Utah, however, the position of the low will allow the southerly flow to advect drier air into southern and eastern Utah, and these two factors will combine to create the potential for critical fire weather conditions on Wednesday, with the potential continuing into Thursday for eastern Utah. The drier air moving in will also likely suppress the threat of convection for Wednesday into much of Thursday.

Guidance looks to be coming into better agreement about the eventual movement of the low, with most members indicating it will move across Utah and southwest Wyoming late Thursday into Friday. There will be enough instability for some showers and thunderstorms, primarily for northern Utah, but moisture will be a limiting factor, as will the weakening of the storm system as it opens up. A perhaps more noticeable impact will be on temperatures, which are likely to drop to values much closer to seasonal normals by Friday afternoon.

Behind the exiting trough, most guidance indicates a drying and warming trend for the upcoming weekend into day seven.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist for the entire airspace through the period. Winds will stay southerly and increase overnight and stay gusty through the day tomorrow. Moisture will move up through the eastern half of the airspace overnight with isolated convection developing during the day tomorrow. Erratic gusty outflow winds and frequent lightning will be possible.

FIRE WEATHER

Strong southerly winds are expected to begin developing on Tuesday afternoon, primarily over the western third of Utah. Wind gusts in excess of 30 mph pairing with relative humidity around 13-17% will create areas of near-critical fire weather conditions, with isolated critical fire weather conditions developing where fuels are critically dry in southwest and west- central Utah. These strong winds will shift into the eastern Utah valleys on Wednesday and Thursday (mainly in central and southern Utah) and will pair with relative humidity around 10-15% to create the potential for critical fire weather conditions for multiple days. There is generally high confidence that critical fire weather conditions will develop across western Emery and Carbon Counties, with moderate confidence in similar conditions developing in eastern Garfield and Kane Counties. After Thursday, a cooling and moistening trend is expected into Friday with conditions warming and drying from Saturday forward.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Fire Weather Watch from Wednesday afternoon through Thursday evening for UTZ484-489-494-498.

Wind Advisory from noon Tuesday to midnight MDT Tuesday night for UTZ115-122.

WY...None.