textproduct: Salt Lake City

KEY MESSAGES

- Increasing moisture aloft ahead of an approaching system will result in scattered showers and thunderstorms across southwest Wyoming, the Utah mountains, and the eastern half of Utah on Sunday.

- An upper-level disturbance moving across the Desert Southwest will draw deep tropical moisture from Hurricanes Odalys and Polo into the region Monday into Tuesday, bringing an increased risk for flash flooding across portions of southern and eastern Utah.

- Drier, more seasonable conditions develop mid-week and persist through at least Friday.

DISCUSSION

A dry southwesterly flow remains in place over Utah this evening. Upstream, an upper trough is strengthening off the PacNW coast. Meanwhile, Hurricanes Odalys and Polo continue to spin in the eastern Pacific.

The upstream trough will carve south towards the northern/central California coast on Sunday, with southwest flow continuing over Utah. Meanwhile, a weak vort lobe originating near Hurricane Odalys will become absorbed into the southwesterlies and lift across Utah during the afternoon. This weak disturbance will bring increased moisture and isolated to scattered showers and thunderstorms to Utah by Sunday afternoon, generally focused over and near the spine of Utah.

As the trough develops into a closed low over southern California and far southern Nevada on Monday, Hurricane Polo will track northeast, moving into Baja California. Moisture from the hurricane will become ingested into the southwesterly flow ahead of the closed low and increase into southern Utah. This will continue to bring the potential for widespread and locally heavy rain, especially across southern and eastern Utah as the closed low crosses from California into Arizona Monday through Tuesday.

Model QPF continues to creep up for the Monday-Tuesday timeframe, especially notable on the lower end of the probabilistic spectrum (NBM 25th percentile values now in excess of 0.6 inches for the bulk of south-central and southeast Utah), which increases confidence in wet conditions. A good portion of south-central through southeast Utah has a 60-70% chance of exceeding 1 inch Monday through Tuesday, highest along the Arizona border. Precipitation amounts will decrease farther north and east into Utah, with east-central Utah having a 60-70% chance of exceeding 0.5 inches, and areas farther north and east with a 30% chance or less.

The heavy rain will bring an increased risk of flooding/flash flooding to the area. The WPC Excessive Rainfall Outlook now has a Moderate Risk across portions of southern Utah, and the Slight Risk now extends into central and portions of northeast Utah. Although model instability is increasing, especially across southwest Utah, precipitation may well end up as largely stratiform with embedded convective elements, and the strength and coverage of these convective elements will most likely determine the extent of any significant flash flooding.

Cooler temperatures will spread into the area Monday and Tuesday, with afternoon maxes falling to around 4-10 degrees below normal and largely failing to rise above the low to mid 70s in most valleys. Temperatures will slowly rebound midweek as the storm system exits the area. There is still some model spread with regards to the large-scale pattern for the latter part of the week. Some models have been trying to bring a trough back into the area, but based on cluster analysis of global ensembles, it appears that any trough may end up being relatively weak.

AVIATION

KSLC...Southerly winds are expected to gradually increase overnight, with occasional gusts to around 25 kts beginning after sunrise and carrying on through the day. Southerly winds are favored to persist. VFR cloud cover will also gradually increase as moisture continues to move into the area. Shower chances will increase Sunday night into Monday morning, particularly after around 09Z or so.

REST OF UTAH AND SOUTHWEST WYOMING...Moisture associated with an approaching trough and remnant tropical system will increase through the TAF period. The enhanced south to southwesterly flow will favor such a direction at most area terminals, with gusts 20-30 kts developing after sunrise and on through the day. VFR cloud cover will also increase. There is around a 20-30% chance of showers and thunderstorms developing Sunday afternoon, primarily along and just east of Utah's high terrain and into southwest Wyoming.

FIRE WEATHER, Issued 132 PM MDT Sat Sep 26 2026

Increasing southerly flow aloft through the remainder of the weekend will result in gusty afternoon winds developing across the western portion of the state through Sunday, with widespread gusts 25-30 mph. While conditions remain dry today, especially across portions of southern Utah where daytime RH values dip to near-critical, improving overnight recoveries tonight will limit the fire weather risk overall. Moisture associated with two tropical systems in the Eastern Pacific will increase steadily on Sunday, with best moisture availability focused across southern and eastern Utah. This will result in scattered showers and thunderstorms developing across these areas on Sunday afternoon, with the main threat being gusty and erratic outflow winds as lower levels remain relatively dry. Deep moisture overspreads the region Monday into Tuesday; concurrently, an upper-level wave traversing the western US will result in ample instability developing across southern and eastern Utah on Monday afternoon. This increasing instability will interact with deep tropical moisture, resulting in more widespread showers and thunderstorms capable of producing heavy rainfall and better chances for widespread wetting rains through Tuesday morning.

SLC WATCHES/WARNINGS/ADVISORIES

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