textproduct: Salt Lake City

KEY MESSAGES, Issued 1019 PM MDT Fri Aug 21 2026

- Monsoonal moisture will continue to spread across Utah and southwest Wyoming through Saturday, bringing an increased threat of thunderstorms that could produce heavy rainfall capable of flash flooding. - Moisture will decrease somewhat Sunday into Monday, with the potential for more substantial drying for at least northern Utah and southwest Wyoming late in the upcoming week.

DISCUSSION, Issued 1019 PM MDT Fri Aug 21 2026

An elongated ridge of high pressure is centered roughly over the Four Corners region this evening. The resultant southerly flow aloft has allowed for monsoon moisture to spread northward across the southern three-quarters of the forecast area. Satellite derived PWs indicate values of 1.0 inch or above for that part of the area, with the moisture continuing to move northward. Embedded shortwave energy in the flow is allowing an area of showers and thunderstorms to continue tonight over central Utah, with the showers continuing to track northward for the remainder of this evening and into the early part of the overnight hours before dissipating.

With ample moisture in place tomorrow, will see another round of scattered showers develop during the afternoon. Absent a well defined forcing mechanism, these will be primarily focused over the higher terrain. This will tend to limit the potential for valley convective activity, but would not be surprised to see a few showers pop up away from the terrain. Forcing is expected to be enhanced again during the evening and early overnight hours, this time from a frontal boundary ejecting from a Pacific Northwest storm system. Given the front will be very much outrunning its associated forcing, think associated precipitation will be scattered in nature, primarily focused over northwest Utah.

The front is expected to bring a very slight dip in temperatures Sunday or northern portions of the area, bringing highs within 5F of seasonal normals. However, its passage combined with flattening of the ridge as the Pacific Northwest system tracks over the top of it will add a westerly component to the flow aloft, advecting some drier air in through Monday. This does not look to be substantial drying by any means, but there is a high chance of some areas seeing PWs as low as the 0.6 to 0.8 inch range, which could bring minimum relative humidity values back close to critical values for portions of western Utah. This could also act to decrease coverage of afternoon showers and thunderstorms, but as we saw earlier this week, there's a good chance that the decrease would not be substantial.

Spread in the guidance increase quite a bit for the middle to latter part of the week, putting confidence in the long term forecast a bit lower than usual. For Wednesday into Thursday, another Pacific Northwest trough is expected to move over the top of the Four Corners ridge, and ensembles seem to be struggling with how much the trough interacts with the ridge. Some guidance (the GFS, for example) shows only minor flattening of the ridge, which would keep at least some moisture over most of the area into the upcoming weekend. However, in solutions where the interaction brings more substantial flattening of the ridge (e.g. the latest EC), the more zonal flow would bring more dramatic drying. Will wait and see where things end up landing.

AVIATION

KSLC...VFR conditions will persist for the KSLC terminal through the period. Dry conditions will continue through the mid afternoon before isolated convection develops during the mid afternoon with ~30% chance of impacting the terminal. This activity becomes less convective and more showery overnight. Winds will be light and diurnally driven aside from variable and gusty winds associated with precipitation near the terminal.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist for the entire airspace through the period. Conditions across the northeastern airspace are starting to dry. Dry conditions will persist through the early afternoon before more convection develops, primarily across the northern 2/3rds of the airspace. This activity will transition to more showery precipitation across the northern airspace overnight. Winds will remain light and diurnally driven aside from gusty and erratic winds near any showers or storms.

FIRE WEATHER, Issued 401 AM MDT Sat Aug 22 2026

Light rain continues to linger across northern Utah that will dissipate by early morning. Moisture will remain elevated across the region with more storms developing Saturday afternoon. Most models have the southern 1/3rd of Utah remaining relatively dry today with most of the activity across central and northern Utah. These storms that develop today will likely weaken and linger into the overnight hours across northern Utah, similar to the activity that occurred tonight. These afternoon storms will be capable of frequent lightning along with gusty and erratic winds.

After today moisture will gradually start to decrease across the region, particularly across southern Utah. Precipitation chances will remain through midweek before flow aloft becomes more westerly during the second half of the week. This will bring much drier air into the area with minimum relative humidity decreasing back into the teens with recoveries in the 30s and 40s. Winds will also be increasing as conditions dry.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Heat Advisory until 7 AM MDT this morning for UTZ101>106.

WY...None.