Washington, UT Weather

Key Messages

- Widespread precipitation returns Wednesday morning across southern Utah, with coverage expanding northward through Friday. Many areas will see precipitation accumulations between 0.5-1.5" through this period, with locally up to 2.0-2.5".

- The heavy rain will bring a threat of flash flooding to southern and central Utah, and there is a Slight Risk of Excessive Rainfall across southern Utah Wednesday and Thursday.

- A few strong thunderstorms may be capable of producing gusty winds and hail across southern Utah on Wednesday and statewide on Thursday. A Marginal Risk for severe thunderstorms is in place on Wednesday across far southern Utah.

- The late week storm will also bring modest snowfall to the high terrain across northern Utah on Friday, with 3-6" possible mainly above 9000 feet, with locally higher amounts.

Discussion

Satellite imagery this afternoon and evening has been visually impressive as a strong closed low circulates and moves southward off of the west coast. This system continues to be the main story in Utah's weather through the work week. Late this evening, isolated showers will develop primarily across higher terrain and the northern Wasatch Front, but will be largely unimpactful with little to no QPF expected.

As the aforementioned closed low begins to inch closer late Tuesday, increasing southwest flow will draw moisture of tropical origins northward into southern Utah. Alongside upper-level diffluence and jet support, precipitation chances will increase, particularly early Wednesday morning across southern Utah. Models have trended earlier with the onset of this precipitation, with more widespread showers beginning after 6AM Wednesday across the south, expanding into northern Utah as early as mid-afternoon.

Thunderstorms on Wednesday have the potential to be a bit more organized across southern Utah. Given a favorable environment with better instability, moisture, and shear in place ahead of the approaching system, gusty winds and hail will be the main threats. However, with southeasterly to easterly surface flow veering to southwesterly not far above the surface, a tornado cannot be ruled out, especially considering low LCLs.

Widespread precipitation will continue through Thursday as the closed low slowly pushes eastward. Flash flooding will remain a threat, particularly for prone areas such as slot canyons and dry washes. By Friday morning, cold air will push into the state as the trough axis passes overhead. Snow levels will drop to 7500-9000ft as 700-mb temperatures dip to -3C to -6C by late Friday. As such, snow accumulations of 3-6 inches above 9000ft across the northern mountains are expected, with perhaps a bit more across higher elevations in the Wasatch and Uintas.

While forecast confidence heading into the weekend is still low, model guidance suggests warmer and drier weather to come.

Aviation

KSLC...Dry conditions will persist through the overnight hours. Winds will shift from light northerly to light southerly between 02- 03Z. Ceilings near 7000 feet will develop Tuesday afternoon with a 10% chance of showers and thunderstorms after 1200 Tuesday.

REST OF UTAH AND SOUTHWEST WYOMING...Winds will remain mainly diurnally driven through Tuesday morning at all terminals. Isolated to widely scattered showers will continue across central and southern Utah, with occasionally lower ceilings through 04-06Z. Showers and thunderstorms will redevelop across much of the area again Tuesday afternoon and evening.

Slc Watches

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