Trenton, Utah Weather Forecast Discussion

076
FXUS65 KSLC 042120
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
320 PM MDT Sat Oct 4 2025
.SYNOPSIS...The Pacific system will continue to move east through
tonight with precipitation chances gradually diminishing throughout
the evening tonight and colder air filtering into the area. The past
24 hours have been quite the gullywasher with widespread
precipitation totals along the Wasatch front ranging from 1-2". The
highest amounts were observed across the Tooele and Rush Valleys
with multiple sites reporting 2.5-3". Chances for rain return as we
approach the weekend with tropical moisture advecting north across
UT.
&&
.DISCUSSION...
Key Messages:
* Scattered showers will persist across northern UT and southwest WY
  through later this evening. Northwest flow across the Great Salt
  Lake may help showers hang on longer near SLC.
* A dry pattern will develop with a ridge of high pressure settling
  in over the Southern Plains with weak flow aloft. Temperatures
  will gradually increase throughout the week.
* Frost development overnight appears likely this evening and
  tomorrow evening across the majority of UT high terrain. Below
  freezing temperatures persist across most of our high terrain with
  a chance the Cache Valley and some lower lying areas of SW WY
  reaching near or below freezing through Tuesday morning.
* Tropical Storm Octave and an area of unsettled convection,
  presumable the next EPAC system, currently churning off the west-
  central coast of Mexico complicate the forecast in the long term.
  Around 70% of ensemble members indicate that tropical moisture
  advects north by Friday.
Rain showers will continue tapering off through the
evening as a potent upper trough progresses east. However, a
favorable northwesterly wind orientation will persist through the
evening resulting in lake effect showers likely persisting through
midnight in some capacity for SLC. With the trough shifting east
tomorrow, a trailing lobe of vorticity will traverse across northern
UT and SW WY tomorrow afternoon giving us another shot of scattered
showers and perhaps thunderstorms. PoPs generally range from 30-50%
with the higher end values across the higher terrain as ascent is
expected to remain generally weak, thus relying on terrain influence
somewhat.
Following this, a dry pattern develops with ridging developing over
the Southern Plains putting our forecast area along the northwestern
axis of the ridge. Weak flow aloft will generally yield calmer
weather, and with building heights over the area, a gradual warm-up
through the workweek. Overnight temperatures statewide will
generally be near-normal for most lower elevations, though our
higher elevations appear to be around 5 degrees below normal as an
anomalously cold airmass passes overhead. Daytime highs tomorrow for
the entire forecast area, besides lower Washington county, are
forecast to be around 10 degrees below normal. By Wednesday, high
temperatures are forecast to be about 5 degrees above normal across
the majority of the forecast area. Unfortunately, this does mean
that the fresh snow across the higher elevations will likely melt,
so get up and experience it while you can!
As we approach the weekend, the forecast becomes quite murky as
Tropical Storm Octave and another disturbed area of convection in
the EPAC appear to greatly influence the forecast going into the
weekend. Looking into cluster guidance initially doesn`t offer much
help as each cluster supports a vastly different solution than the
others with respect to timing and the strength of each trough/ridge
featured in the upcoming upper air pattern. Despite this, ensemble
guidance continues to hone-in on tropical moisture from the two
aforementioned storms in the EPAC making its way up to at least
southern UT by Friday with ~70% of members continuing to support
this solution. This is due to another longwave trough pushing into
the Pacific NW with the two storms phasing into the mean flow. What
this tells us is that chances for rain are likely to return by the
end of the workweek, though spatial extent and magnitude still
remain quite uncertain at this time. However, with the position of
the developing ridge over the Southern Plains and our position along
the NW quadrant, this typically would support a favorable upper air
pattern for unsettled weather returning to the area.
&&
.AVIATION...KSLC...Light to moderate rain will continue through
around 23-00z before transitioning to more intermittent showers
through around 03z. After 03z, there is a 20 percent chance of
showers through the night and into Sunday morning. MVFR conditions
and mountain top obscurations are likely to continue through 23-00z,
with brief IFR conditions possible. This evening and overnight, VFR
conditions are expected to prevail, with periodic MVFR conditions
possible in heavier showers. Southerly winds are currently expected
to switch to northwesterly by 22-23z, but there is a 25% chance that
winds will remain southerly.
.REST OF UTAH AND SOUTHWEST WYOMING...Periods of light to moderate
rain will continue across northern Utah and southwest Wyoming
through around 00z before transitioning to more isolated to widely
scattered rain showers for the rest of the night. Areas of MVFR
conditions with localized IFR conditions along with mountain top
obscurations will continue in these areas through at least 22-00z.
This evening and overnight, VFR conditions are expected to prevail,
with local MVFR conditions possible in heavier showers. Across
southern Utah, expect scattered cloud cover into the early evening
hours before skies gradually clear out through the night. Otherwise,
winds through this evening will remain generally westerly to
northwesterly areawide, locally variable due to showers, before
winds decrease and trend more diurnal later tonight.
&&
.FIRE WEATHER...The storm system continues to move east through
today which has provided a wetting rain across the majority of
northern UT with a widespread 1-2" of rain on average reported.
Additionally, snow is currently ongoing across elevations generally
greater than 9000ft with light rain ongoing across lower elevations.
Later tonight, conditions are expected to dry out with another round
of showers and thunderstorms tomorrow afternoon across northern UT.
A dry pattern settles in across the state through at least Friday,
though chances for rain develop once again on Friday across the
majority of the state as moisture moves in from the south.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
PUBLIC...Worster
AVIATION...Cheng
FIRE WEATHER...Worster
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion