textproduct: Salt Lake City

KEY MESSAGES

- Numerous Flood and Flash Flood Warnings remain in effect for southern and eastern Utah, as widespread moderate to heavy precipitation persists through this evening.

- There is a Marginal Risk (level 1 of 5) for severe thunderstorms much of Utah through this evening, with a threat for large hail and damaging winds.

- Accumulating snowfall is expected across the higher terrain of northern Utah tonight into Friday morning, with 1-4" likely above 9000 feet. There is a chance of locally higher amounts for favored locations.

DISCUSSION

Tropical moisture in place across the forecast area will continue to fuel widespread showers and thunderstorms through this evening, as an upstream low along the California coast makes its way through the Great Basin. Ample deep layer shear will maintain a favorable environment for organized convection including supercells anywhere sufficient breaks in the cloud cover allow for destabilization, as has been evidenced across southwest Utah over the past few hours. Efficient rainfall rates will also continue to result in excessive runoff. Most large drainages across south central into east central Utah are already running high and fast, and as such Flood Warnings are in effect for these areas.

A shortwave trough rounding the base of the upstream low will lift across the forecast area this evening, focusing the heavier precipitation further north into northern Utah/southwest Wyoming. Initially a band of showers and thunderstorms, potentially strong to severe, is expected to propagate across northwest Utah reaching the Wasatch Front this evening, followed by a fairly broad stratiform region of precipitation associated with the passage of the upper trough. Snow levels will fall to roughly 8000 feet overnight, with accumulating snow largely above 9000 feet. Previous forecast totals of 1-4" with locally higher amounts still look reasonable, with a few locally higher totals if precip is able to linger into Friday morning.

As the initial low ejects into the northern Rockies, a secondary upper low is forecast to form over the Desert Southwest Saturday, then slowly translate into the central/southern Rockies Sunday. This will maintain cool temperatures across the forecast area, along with a chance of precipitation mainly across the eastern third of the CWA. An upper trough across the Pacific Northwest looks to keep temperatures near to slightly below climo for much of next week.

AVIATION

KSLC...Off and on showers expected through Thursday evening and early portion of the overnight. There will be a chance of embedded thunderstorms from mid afternoon into the evening. There is ~10-30% chance of MVFR CIGS/VIS during periods of heavier precipitation, especially in thunderstorms. Shower chances will finally decrease after around 09Z Friday, but isolated shower redevelopment is then supported Friday afternoon. Winds are generally favored to remain southerly, with occasional gusts 20-30 kts or so, possibly higher in thunderstorms. Some variability also possible in thunderstorms.

REST OF UTAH AND SOUTHWEST WYOMING...Active weather across the region with widespread scattered showers and thunderstorms. There is ~10-30% chance of MVFR CIGS/VIS developing in times of heavier precipitation, or especially thunderstorms. Precipitation will tend to decrease in coverage at all but far northern terminals late Thursday evening into the overnight hours. Winds at most terminals will favor a southerly direction, with some gusts around 15-30 kts or so. Some higher gusts and periods of variability will be possible in and around thunderstorms.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Flood Watch through this evening for UTZ117-120-121-123>131.

WY...None.