820 FXUS65 KSLC 142159 AFDSLCArea Forecast Discussion National Weather Service Salt Lake City UT 359 PM MDT Sun Sep 14 2025
.SYNOPSIS...High pressure departs and gives way to a quick grazing system and associated cold front to start the week. This will bring cooler temperatures and some light precipitation to N UT and SW WY. A drying and warming trend then sets in through midweek, with moisture and precipitation chances returning late in the week.
&&
.SHORT TERM (Through 12Z/6AM Tuesday)...Afternoon water vapor loop shows a transient ridge shifting through the Great Basin and into the Intermountain West as the trough which brought a period of unsettled weather continues to depart to the east. This ridge is bringing much quieter conditions to Utah and southwest Wyoming today, with little of note on radar. Visible satellite however is picking up on a fair bit of cumulus developing along the northern high terrain and eastward. Overall though, pretty pleasant conditions across the area with afternoon temperatures running fairly close to normal for mid September.
As quickly as the ridge shifted in, it will depart tonight as it gives way to an approaching PacNW trough. This trough will push an associated cold frontal boundary southward into Utah and southwest Wyoming, accompanied by some showers and potentially a thunderstorm or two given modest instability with pockets of MUCAPE around 100 J/kg or so. With the grazing nature of the trough, the front won`t advance too far southward, with precipitation generally along/north of the I-80 corridor or so. As the day progresses precipitation chances will actually gradually decrease, becoming more focused over southwest Wyoming and the Uinta Mountains by the afternoon. At locations behind the front across northern Utah and southwest Wyoming, afternoon high temperatures dip around 3-7F in comparison to Sunday.
Overnight into Tuesday morning a reinforcing lobe of the trough will pivot through and help reinvigorate some low end (~10-30%) chances of showers across some of the high northern terrain, particularly the Uinta Mountains. Otherwise, it`ll be a cooler night at areas where the front passed, with some potential for patchy frost noted across some of the higher mountain valleys like the Wasatch Back.
.LONG TERM (After 12Z/6AM Tuesday), Issued 341 AM MDT... A shortwave ejecting to the east will leave conditions dry on Tuesday with temperatures near normal along with temperatures a few degrees above normal further south. A ridge builds into the area on the heels of this shortwave with temperatures gradually warming a few degrees above normal Wednesday and Thursday. Temperatures across lower Washington county will be in the upper 90s to near 100 degrees.
The ridge starts to break down a bit late in the week with southerly flow advecting moisture back into the area. This will help to develop diurnal convection through the weekend. A trough off the west coast will bring upper level diffluence to provide more lift for convection across the area on Saturday. ~56% of ensemble members are on the wetter side of the solution, while the remaining 44% of members are on the drier side of the solution space. Additionally, guidance does hint at some shortwaves ejected out ahead of the parent trough over the weekend that could enhance lift and promote more convection. This pattern will favor temperatures near normal given the absence of any cooler continental airmasses.
&&
.AVIATION...KSLC...VFR conditions are expected through the TAF period under clearing skies through the evening. Light northwesterly winds are expected this evening, transitioning back to southerly flow around 02-03Z. Clouds will increase again through the overnight hours but remain around 10kft or higher, with around a 20-30% chance of light rain around 11-12Z.
.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected across Utah and southwest Wyoming through the TAF period. Gusty west to southwest winds will persist through sunset, reverting back to diurnally driven flows thereafter. Across northern Utah and southwest Wyoming, an area of light showers is anticipated to develop after 05Z, bringing isolated to scattered precipitation from KSLC northward through 14-15Z.
&&
.FIRE WEATHER...Sunday`s high pressure and dry conditions will depart and give way to a grazing system Sunday night into early next week. An associated cold front will be pushed southward into northern Utah, bringing some chances of light showers. Instability will be limited but non-zero, so cannot entirely rule out a thunderstorm or two. Precipitation chances will be highest along and north of the I-80 corridor, with a reinvigoration of low end precipitation chances Monday night into Tuesday as a reinforcing system grazes the area. Thereafter into the middle portions of the week a drying and warming trend is noted, with widespread daytime minimum humidity values in the teens at most lower elevation areas. Moisture is then favored to return to the area from Friday into the weekend, bringing a corresponding return of precipitation chances.
&&
.SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. &&
$$
SHORT TERM...Warthen LONG TERM...Mahan AVIATION...Webber FIRE WEATHER...Warthen
For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity
NWS SLC Office Area Forecast Discussion