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Fremont, Utah Weather Forecast Discussion

034
FXUS65 KSLC 212120
AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 320 PM MDT Sun Sep 21 2025

.SYNOPSIS...An unsettled pattern persists into Monday along with a cooldown at many locations following the passage of a cold front. Drier conditions are then expected through midweek, with some moisture starting to return to southern Utah late in the work week.

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.DISCUSSION... Key Messages: * Scattered showers and thunderstorms continue across northern Utah through Monday, with the best chance of wetting rain across northern Utah late Sunday night through early Monday morning. * Minimally impactful elevated canyon winds are expected early Tuesday morning for Washington County canyons with even more limited canyon winds possible for Davis and Weber County canyon exits Tuesday morning as well as Tuesday night into Wednesday morning. * Temperatures trend below normal Monday through Tuesday with temperatures then moderating back to, and just above, normal Wednesday into Thursday with generally dry weather in place.

This afternoon a weak convergence boundary over northern Utah, roughly along and south of the I-80 corridor is helping to invigorate isolated to widely scattered showers and thunderstorms. With limited instability in place along this axis, showers and thunderstorms along this axis are generally expected to remain on the weaker side with some isolated briefly moderate to heavy rainfall. Meanwhile, back to the west, a trough moving in through Washington and Oregon is helping to H5 heights across northeast Nevada and southern Idaho, which is coincident with a better pool of instability and a bit more vigorous convection. High res ensembles are in excellent agreement that this well forced area of convection will move across northern Utah tonight, with a general consensus of showers and thunderstorms moving through the Wasatch Front between 10pm and 1am, and eventually across SW Wyoming and the Uinta Basin through 3-5am, while weakening. While ensemble means are generally around 0.05 to 0.15 inches for precipitation overnight, the upper range of potential is as high as 0.5 to 1 inch of precipitation where any heavier showers and thunderstorms are able to reside, with the best corridor for this locally heavier rain somewhere between Salt Lake and Utah Counties. A trailing line of showers and thunderstorms will then move across northeastern Utah Monday morning through early afternoon as the trailing upper level vort max moves through southwest Wyoming, with the associated convection moving off into eastern Utah by Monday afternoon.

Behind the cold front on Monday morning, temperatures will trend below normal with highs only in the low to mid 70s across northern Utah valleys for Monday and Tuesday. Drying conditions will bring generally pleasant weather by Tuesday. Initially the northerly winds late Monday night into Tuesday morning with increasing pressure gradient across southern Utah will help develop some limited canyon winds across Washington County including out of Blackridge Canyon. Current guidance suggests sub-advisory winds generally in the 30 to 40 mph wind gust range. Similarly across northern Utah a weak easterly pressure gradient will develop across the Wasatch, but with very light 700 winds and minimal temperature advection, expect only limited canyon winds to develop Tuesday morning and again Wednesday. Again winds look sub-advisory there as well, with gusts in the 25 to 40 mph range but only for areas very close to prone canyon exits, primarily in Davis and Weber Counties.

For the remainder of the extended forecast, a general warming trend will bring temperatures back to and just above normal by the second half of the week. Generally dry conditions will remain in place through mid-week. However by the end of the week, there is potential for moisture sneaking back into southwest Utah. There remain more uncertainty that usual with this increase in moisture as it is dependent on the track of a slowly meandering upstream cutoff low moving onshore. Overall the ensemble mean has trended toward evolving this trough southward into Arizona as we move into next weekend. Thus southern Utah will likely remain on the periphery of the deeper moisture, but this will still increase the chances for daily isolated to scattered showers and thunderstorms.

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.AVIATION...KSLC...VFR conditions will persist for the KSLC terminal through the period. Mostly dry conditions will likely continue for the remainder of the afternoon with rain and embedded thunder returning between ~04-07Z ahead of a cold front. Cold front passage will occur ~15Z tomorrow with some spotty showers along and behind the front in addition to a northerly wind switch.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist for the airspace through the period. Conditions across the southern airspace will remain dry. Isolated and short lived afternoon convection will gradually diminish across the north with a return of some rain with embedded thunder late tonight in advance of a cold front. Frontal passage timing across the north will occur between 12- 17Z with winds shifting out of the north. Spotty showers along and behind the front are expected.

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.FIRE WEATHER... This afternoon isolated to scattered showers and thunderstorms will impact areas roughly along and just south of the I-80 corridor in northern Utah. Drier air in place across southern Utah with high pressure building over southern Utah will keep dry conditions in place. Tonight an approaching low pressure system will bring a more organized area of showers and thunderstorms from west to east across Northern Utah overnight. This is when the greatest chance of wetting rain will occur over northern Utah. Ensemble means range from around 0.05 to 0.15 inches of rain over northern Utah, but where thunderstorms are able to be more focused a half inch to three quarters of an inch of rain cannot be ruled out.

On Monday, a cold front will move across northern Utah which may bring a reinforcing round of scattered showers and thunderstorms particularly across northeastern Utah along with trending temperatures below normal for Monday and Tuesday, with valley high temperatures only in the low 70s across northern Utah. Southern Utah will remain dry through this timeframe.

Temperatures will moderate Wednesday through the end of the week, trending back to near normal to slightly above normal by Thursday, with generally dry conditions in place Tuesday and Wednesday. By Thursday into the weekend, limited moisture will start to work its way back into Utah from the southwest. This will eventually start to increase the chances for isolated to widely scattered showers and thunderstorms by late in the week.

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.SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. &&

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PUBLIC...Church AVIATION...Mahan FIRE WEATHER...Church

For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion

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