textproduct: Salt Lake City

KEY MESSAGES, Issued 1044 PM MDT Tue Sep 15 2026

- Deep moisture will continue to bring an elevated threat of flooding to portions of southern and eastern Utah through at least Friday.

- A Flood Watch for flash flooding has been issued from late tonight through Thursday morning for portions of southern and eastern Utah including Zion National Park, Capitol Reef National Park, Glen Canyon Recreation Area, the greater Grand Staircase- Escalante National Monument area, and the lower Paria including Buckskin Gulch and Paria Canyon north of the Arizona border.

- A marginal risk for severe thunderstorms (level 1/5) continues for Wednesday morning into Wednesday afternoon across portions of northern Utah.

- A marginal risk for excessive rainfall (level 1/4) continues for Thursday and Friday across southern and eastern Utah.

DISCUSSION, Issued 1044 PM MDT Tue Sep 15 2026

An upper level low will continue to shift down the Pacific Coast through later Thursday into Friday and then gradually eject across the Great Basin through Saturday. Diffluent southwest flow will remain in place, with modest moisture transport through at least later Thursday. Embedded in this southwest flow will be a multitude of weak shortwave troughs or remnant MCVs. This, combined with PWATs in the 96-99th percentile, and broad ascent will support periods of convection with very heavy rainfall, especially through Friday morning.

Earlier thunderstorms, with occasional embedded supercells produced rainfall rates as high as 0.50 inches in 20 minutes, causing multiple flash floods in the Wahweap, lower Paria drainages as well as various slot canyons in the San Rafael Swell including Little Wildhorse north of Goblin Valley State Park.

Current model trends indicate another subtle shortwave ejecting across northern Arizona/southern Nevada and southwest Utah will aid in the development of convection overnight through about 6 AM this morning across lower Washington County, Iron County and western Kane and Garfield Counties. Rainfall rates in excess of 0.25 inches an hour will be possible with this convection, with around a 10% chance of rainfall rates in excess of 0.50 inches per hour. A Flood Watch for flash flooding begins at midnight tonight and continues through Thursday morning for Zion National Park and points east. No changes have been made to the going Watch.

The Storm Prediction Center has outlooked portions of northern Utah for a marginal risk for severe thunderstorms, particularly for Wednesday morning into early Wednesday afternoon. A few strong thunderstorms will be possible along the periphery of the deeper moisture in this area.

Afternoon convection will kick off across the region, with a multitude of CAMS showing very widespread heavy rain across most of southern Utah after about 00Z. This may require the expansion of the Flood Watch into lower Washington, Iron and Beaver Counties for late Wednesday night into Thursday afternoon. Something to monitor for future adjustments if CAMS remain consistent.

It is not recommended to have plans into slot canyons, normally dry washes, and other areas prone to flash flooding over the next several days. Nearly all National Park and Rec areas are currently at Probable for the next several days in the flash flood potential product.

AVIATION

KSLC...VFR conditions will persist for the KSLC terminal through the period. A few lingering showers moving south of the terminal through ~14Z will keep the potential for gusty and erratic winds, but primarily gusty southerlies prevail. Conditions will be mostly dry throughout the day with a few highs. Showers and storms are possible (~25% chance) again tonight.

REST OF UTAH AND SOUTHWEST WYOMING...Showers and thunderstorms continue the first few hours of the period, generally ending between 12z and 15z. Gusty winds up to 30 knots and brief MVFR conditions are possible. There will be the chance of showers and thunderstorms again Wednesday afternoon, but chances generally remain under 30 percent. As better moisture moves into the area starting around 00z, shower and isolated thunderstorm chances increase for late in the period. Southern terminals should see prevailing rain around 03z. Models have some disagreement on timing further north, so have mostly PROB30 for now, starting about 06z.

FIRE WEATHER, Issued 344 AM MDT Wed Sep 16 2026

Monsoon moisture will remain in place, particularly across southern and eastern Utah, through the next several days. Frequent lightning along with gusty and erratic winds have been observed with storms today, and these threats will continue with any stronger storms that develop throughout the week. Southwest winds will remain breezy 25-35 mph across western Utah, although min RH should remain above 20% for most locations.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Flood Watch from noon MDT today through late tonight for UTZ121- 129.

Flood Watch through late tonight for UTZ124-128-130-131.

WY...None.