textproduct: Salt Lake City

KEY MESSAGES

- Periods of showers and thunderstorms will continue tonight into Friday, with the best coverage over northern Utah and southwest Wyoming. The focus of showers and storms will gradually shift east during the day Friday. Hail, heavy rain, and lightning will be the primarily threats. Flash flooding remains a threat as well. - Temperatures will be noticeably cooler over the weekend, particularly for northern Utah and southwest Wyoming, with maxes running up to 10F above seasonal normals behind a cold front. That front will steadily draw drier air into the area from the west through the weekend.

- Moisture is expected to increase again beginning Tuesday, with unsettled conditions persisting for much of the upcoming week.

DISCUSSION

A Pacific Northwest storm system is centered near the Idaho/Nevada/Utah triple point this evening, with the associated cold front near a KINS-KEVW line. In a deeply moist and unstable airmass over northern Utah, convection was fairly widespread, with some severe cells along the Wasatch Front that produce hail to golf ball size, strong winds, localized urban flooding, and even one tornado that impacted Davis and Morgan counties. Late this evening, convection is weaker and more localized, with the strongest showers continuing over the frontal boundary.

Convection will tend to diminish during the overnight hours as one lobe of the low exits the area, with another expected to rotate in by Saturday afternoon. The trough is expected to track steadily east during the day Saturday, centered near the Utah/Idaho border. Thus, the focus of convection will move eastward during the day. West to northwest flow behind the low will continue to draw drier air in front the west, steadily decreasing the threat of convection. Behind the front, temperatures for northern Utah are expected to run up to 10F below seasonal normals, with southern Utah temperatures staying closer to normal near the front.

High pressure is expected to move overhead over Utah and southwest Wyoming on Sunday in between the exiting trough and another broad low approaching the California coast. Guidance is in good agreement that the California low will track eastward into the Great Basin by Tuesday, bringing a return of moisture and instability to the area. There still remains a good amount of disagreement in the guidance, however, with regard to the precise track of the system and how much it weakens as it moves onshore. Thus, it is currently difficult to determine the areas that might see more significant convection over the area by midweek, though the ensembles are leaning modestly toward southern and eastern Utah. The track of the low should have little impact on temperatures, which should stay in the vicinity of seasonal normals for much of the upcoming week.

AVIATION

KSLC...VFR conditions with northwest winds will prevail through the TAF period. Lingering showers in the vicinity of the terminal will move away by 06Z. There is a 20% chance for showers and thunderstorms in the vicinity of the terminal after 18Z Saturday.

REST OF UTAH AND SOUTHWEST WYOMING...Showers and thunderstorms will continue to impact KPVU, KHCR and KEVW through the remainder of the evening, before storms taper off after 06Z. Otherwise VFR conditions will prevail at all terminals through the TAF period, with a 20% chance of afternoon showers and thunderstorms in the vicinity of northern terminals after 18Z Saturday.

FIRE WEATHER

Earlier coverage of showers and thunderstorms has diminished significantly, though scattered convection continues, primarily focused along the cold front over northern and central Utah. These storms will continue to diminish overnight, with showers and thunderstorms developing again Saturday afternoon as the associated low tracks eastward near the Utah/Idaho border. With drier air gradually moving in behind it, the focus of showers and thunderstorms will shift east during the day. Any storms that develop will have the potential to produce gusty thunderstorm winds and lightning as well as wetting rainfall. Drier conditions will continue Sunday into Monday under the influence of weak high pressure. However, another approaching Pacific storm system will allow moisture to return to the state as instability increases once again.

SLC WATCHES/WARNINGS/ADVISORIES

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