941 FXUS65 KSLC 162208 AFDSLCArea Forecast Discussion National Weather Service Salt Lake City UT 408 PM MDT Tue Sep 16 2025
.SYNOPSIS...The storm system is expected to push east tonight making way for high pressure with dry and warm conditions Wednesday and Thursday. Moisture returns to the area Friday lingering through the weekend serving to increase chances for rain into early next week.
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.SHORT TERM (After 12Z/6AM Thursday)...The upper low is forecast to continue meandering east at quite the slow pace as a chaotic upper level pattern over the northern plains supports slow movement through the short term. Following the departure of the upper low, transient ridging is forecast to build in its wake with height rises resulting in a brief warmup Wednesday and Thursday. Additionally, northwest flow will result in generally drier conditions across UT and southwest WY.
Tomorrow afternoon, a trailing shortwave on the western periphery of the aforementioned upper low looks to dive south across western WY toward northern UT. While this is occurring, the wave is expected to amplify somewhat as it approaches some residual moisture located across southwest WY, the Uintas, and far northeast UT, particularly Duchesne county where confidence is somewhat higher due to slightly better moisture quality. Elsewhere, conditions should remain quite dry throughout the day through the overnight into Thursday morning.
.LONG TERM (After 12Z/6AM Thursday), Issued 336 AM MDT... By Thursday, Utah and southwest Wyoming remain under high pressure, sandwiched in between the exiting low to our east and a weak circulation over southern California. Thus, conditions will be largely quiet on Thursday, with clear skies and near-normal temperatures across most of the area.
By late Thursday, however, moisture will begin to push into the area from the southwest as the aforementioned California low nudges the ridge axis to our east. With subtle upper-level diffluence within this increasing moisture, chances for shower and thunderstorm development will increase during the overnight hours. There is still some uncertainty regarding timing, thus the spatial extent of these nocturnal showers is still yet to be determined. This moisture will quickly overspread the rest of the state through the day on Friday, resulting in more scattered showers/thunderstorms. As this weakening low ejects across northwestern Utah, increased shear could produce more organization with these storms on Friday/Saturday afternoons.
Ensemble guidance suggests moisture peaks by Saturday, with an overall downward trend thereafter as relatively zonal flow brings in a drier air mass across at least northern/central Utah and southwest Wyoming. Across southern Utah, there is much lower confidence in when/if this moisture exits. Confidence is, however, increasing in the longwave pattern heading into next week, with models largely convening on a ridge building across the western US, with a cutoff low rotating near southern California by Day 7.
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.AVIATION...KSLC...Quieter conditions will continue to settle in as system departs. Precipitation chances remain low through Wed, and skies remain clear to mostly clear with some very limited cumulus development Wed afternoon. Winds remain fairly light and are expected to follow a typical diurnal direction pattern (becoming south between 02-04Z Wed, NW between 16-18Z Wed).
.REST OF UTAH AND SOUTHWEST WYOMING...Slow moving system will continue to depart the region to the east. NE UT and SW WY will see just enough lingering moisture/influence to result in modest chances (~10-30%) of convection Wed afternoon. Otherwise, drier and quieter conditions are expected at most area terminals with clear to mostly clear skies and fairly light wind magnitudes.
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.FIRE WEATHER...Chances for showers and thunderstorms will gradually diminish this afternoon as the storm system progresses east. Following this, high pressure develops in its wake bringing drier and warmer conditions to UT on Wednesday and Thursday. Following this, moisture returns to the state on Friday across southern UT as southwesterly winds develop. Moisture will continue to overspread the state throughout the weekend increasing chances for showers and thunderstorms, perhaps continuing into next week.
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.SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. &&
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SHORT TERM...Worster LONG TERM...Cunningham AVIATION...Warthen FIRE WEATHER...Worster
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NWS SLC Office Area Forecast Discussion