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. Heavy rain, gusty winds, and hail will be the primarily threats.

- A cold front will bring drier conditions with more seasonable temperatures Saturday through the remainder of the weekend with moisture expected to increase again to start the work week.

DISCUSSION

Utah and southwest Wyoming remain under a moist, unstable, and breezy southerly flow this evening in between high pressure over the central United States and a broad low over the California coast. Satellite derived PWs are in the 0.7 to 1.0 inch range across the area, with the highest values over southeast Utah. The position of the upper jet on the front edge of the low has brought the best divergence roughly to northeastern portions of the area with a weak wave providing additional instability, particularly to areas north of I-70 and east of I-15, with one storm producing ping pong ball to golf ball sized hail in the city of Midway.

Overall, the current round of showers and thunderstorms is on the decrease with a lack of daytime heating, with just a few stronger cells remaining. As a result, have canceled the going Flood Watch for Flash Flooding as the threat has ended. However, as the low slides into Nevada and brings an initial boundary through, showers are expected to light up during the early morning, focused over northern Utah and southwest Wyoming. The low is then on track to graze northern portions of the area as it moves by through Saturday. As a result, looking at the most widespread convection to be on Friday afternoon in association with the main trough and associated cold front. CAMs continue to indicate the best coverage to be over northern portions of the area, but a few storms over southern Utah could bring an isolated threat of flash flooding.

The passage of the system will also have a noticeable effect on temperatures, with highs Friday into the weekend running 5-10F below seasonal normals for northern Utah and southwest Wyoming, and near seasonal normals for southern Utah. As the trough exits, the flow aloft will move to a more west to northwesterly direction, allowing some drier air to move in. With the trough not entirely out of the picture on Saturday, still anticipating some scattered convection focused over northeastern portions of the forecast area, with Sunday expected to be dry with weak ridging moving in.

Guidance indicates the break in the action will be short lived, however, with yet another low approaching the Pacific coast Sunday afternoon. Most guidance shows this system tracking eastward into the Desert Southwest to start the work week, but the ensembles diverge noticeably with the regard to the potential track of the system and how much it will weaken once onshore. Still, confidence is increasing with regard to a relatively quick return to unsettled weather, at least for southern Utah.

AVIATION

KSLC...The SLC terminal will see VFR conditions through the overnight hours with southerly winds. Periodic showers are expected to develop tomorrow morning, most likely between 10Z and 12Z, bringing the potential for periods of gusty and erratic winds through the morning. By the late afternoon, additional scattered showers and thunderstorms are expected to develop, with a 30 percent chance of producing gusty winds through the early evening tomorrow.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected across the airspace through the overnight hours. The current round of showers and thunderstorms over northeastern portions of the area is diminishing, but another round is expected during the early morning, most likely beginning between 10Z and 12Z, focused over northern portions of the airspace, lasting through much of the morning. Additional showers and thunderstorms are then expected to develop by late afternoon, again primarily for northern portions of the airspace. Any storms that develop will have the potential to produce gusty and erratic winds, lightning, and brief mountain obscurations.

FIRE WEATHER

Showers and thunderstorms over northeast Utah are weakening this evening, with another round of showers expected for northern Utah beginning early this morning, lasting into the late morning. More widespread showers and thunderstorms will develop Friday afternoon, with the best coverage over northern Utah. Any storms that develop will have the potential to produce gusty and erratic winds and lightning, with an enhanced chance of wetting rainfall. An associated cold front will bring drier conditions and more seasonable conditions for Saturday, though the threat of showers and thunderstorms will linger over northeast Utah through Saturday afternoon. High pressure will bring dry conditions for Sunday before moisture and instability increase again to start the work week as another Pacific storm system moves onshore. With this system most likely expected to move into the Desert Southwest, coverage should be better for southern Utah compared to northern Utah for the system next week.

SLC WATCHES/WARNINGS/ADVISORIES

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