textproduct: Salt Lake City

KEY MESSAGES

- Gusty southwest winds are expected each afternoon and evening across Utah and southwest Wyoming through the end of the work week.

- Low daytime RH through Thursday across western Utah will result in locally critical fire weather conditions when coupled with gusty winds.

- An influx of tropical moisture over the holiday weekend will increase the risk of flash flooding into early next week, particularly on Sunday across central and southern Utah.

DISCUSSION

A shortwave ejecting off a parent trough currently off the PacNW coast will continue to move eastward across the region today. Modest instability from this shortwave will allow isolated showers and thunderstorms to develop this afternoon along and east of the Wasatch into the Uinta Basin, as well as portions of southeast Utah. The Storm Prediction Center has most of eastern Utah in a Marginal (level 1 of 5) Risk for these storms to produce gusty outflow winds in excess of 58 mph. Conditions across the remainder of Utah and southwest Wyoming stay dry today, with widespread gusty southwesterly winds 30-45 mph prevailing as a result of the aforementioned trough.

The parent trough gradually digs southward along the coast of California Thursday through Saturday, keeping winds elevated across the region each afternoon and evening through this period, especially Thursday and Friday across the western half of Utah. While winds will be gusty each day, gusts in excess of 45 mph are not likely to be widespread and persistent enough, thus not warranting any headlines at this time. A drier airmass and more limited instability will limit chances for afternoon convection across the region through this period.

The weather over this upcoming holiday weekend will be overall dictated by the progression of what is now Tropical Storm Marie, currently situated south of the Baja Peninsula. Prior guidance indicated the advection of deep moisture associated with this storm as early as Saturday, though recent guidance has backed off on this scenario, and delays deepest moisture transport until Sunday. With the aforementioned trough expected to begin gradually shifting eastward Sunday, ample instability will exist across the region for widespread showers and thunderstorms to develop, bringing an increased risk of heavy rainfall and flash flooding to the region. Even small changes to the track of the tropical system could greatly change the magnitude of the moisture influx into our region late this weekend into early next week, so stay tuned to the forecast as we get closer.

AVIATION

KSLC...Gusty southerly winds will continue at the SLC terminal through the afternoon. Expect peak gusts near 35-40kts at times. A weak front will then produce a northwesterly wind shift around 23- 00z. VFR conditions will prevail.

REST OF UTAH AND SOUTHWEST WYOMING...Southerly winds will continue across most sites, with peak gusts to 25-40kts. A weak, shallow front will push through northern Utah by late afternoon, but will struggle to push south of KSLC. Expect isolated thunderstorms with gusty and erratic winds and small hail, largely east of a line from KEVW to KHVE.

FIRE WEATHER

Dry conditions remain in place across the western half of Utah today, with daytime RH values dipping into the low teens. Given strong southwesterly winds with widespread gusts 35-45 mph continuing through this evening, a period of locally critical fire weather conditions is possible across the area, though improvements in fuel moisture may limit the overall threat. Similar conditions exist on Thursday, except for slight improvement in minimum RH values. Across the eastern half of the state, moisture lingering across the area today will result in potential for isolated showers and thunderstorms capable of producing gusty and erratic outflow winds, mainly along and east of the Wasatch and portions of southeast Utah.

RH improves statewide on Friday, which will limit fire weather concerns into the holiday weekend. Winds remain gusty areawide as we remain on the periphery of a low pressure system sitting along the west coast. Little in the way of forcing will limit showers and thunderstorm chances Friday and Saturday, despite increased moisture. This low is expected to eject into our region by Sunday, resulting in a more favorable environment for widespread showers and thunderstorms across the state, with deep moisture supportive of an increased risk for heavy rainfall and flash flooding in sensitive terrain into early next week.

SLC WATCHES/WARNINGS/ADVISORIES

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