Tornado in Utah, April 18, 2025

Area Forecast Discussion
National Weather Service Salt Lake City UT
405 AM MDT Fri Apr 18 2025

.SYNOPSIS...A strong trough will continue to result in some
wintry weather across the region Friday. Clearer weather begins to
settle in for Saturday, but an progressive and somewhat unsettled
pattern looks to take hold for much of the upcoming week
thereafter.

&&

.SHORT TERM (Through 12Z/6AM Sunday)...Morning water vapor loop
shows the base of a broad trough sinking into northern Utah, with
other supporting observations indicating the initial frontal
boundary is continuing to advance south and eastward out of the
area. H7 temps of around -10C or so are accompanying the trough as
it pushes in, and as a result, temperatures in the post-frontal
environment are quite chilly. Additionally, the relative
difference between the warmer lake temperature and cold low level
air is helping in the development of lake effect/enhanced showers
off of the Great Salt Lake. The persistent nature of the band over
the Oquirrh Mountains and adjacent terrain has yielded some light
snow accumulations across eastern Toole Valley and western Salt
Lake Valley, primarily over grassy/elevated surfaces, but also
periodically on road surfaces with sufficiently high snow rates.
As the trough/low continue to slide southward, anticipate flow to
become less conducive for maintained lake effect (at least over
the current areas), so current thinking is any morning commute
impacts from this are likely to be localized at best. Still, will
be something to keep an eye on heading out the door this morning.

Moving into the daytime Friday, aforementioned trough/low will
continue on a southward trajectory. Moisture and forcing will in
turn result in a resurgence of more widespread showers wrapping
around the broader circulation as daytime heating increases. With
snow levels only pushing into the 4500-5000 ft MSL range or so,
anticipate most locations see these showers precipitating in the
form of snow or rain/snow mix. Even then though, the showery
nature in combination with a stronger April sun angle should help
to preclude more appreciable low elevation impacts... Though given
some convective element to the showers, those that may encounter
any while driving around should at least be prepared for briefly
deteriorated conditions (reduced visibility, wet roadways, etc.).
Higher elevation mountain routes, especially for the central and
southern mountains, continue to be areas which will be more prone
to accumulating road snow. Given the projection of the trough/low
circulation, model guidance does also show some consensus on some
light accumulations for the higher elevation portion of the I-15
corridor between roughly Cove Fort and Cedar City, which could be
impactful to those planning travel accordingly.

As early as mid afternoon Friday and lasting potentially late
into the evening hours, flow across northern Utah begins to take
on a more northeast to easterly orientation. As often happens in
these setups, the corresponding gradient aids in creating some
gusty canyon winds in typically prone areas, which is further
enhanced by cold air advection. Overall though, neither ingredient
looks overly impressive, and there remains little evidence of the
formation of much of a ridge top critical layer (the usual third
ingredient) to get a stronger event going. So, while those in
typically prone areas may see some modestly gusty conditions,
still anticipating conditions likely to remain below necessitating
any sort of headline issuance at this time.

Subsidence and dry air both begin to increase later Friday night
on through Saturday as the trough continues on its path and weak
shortwave ridging starts to nose in from the west. In turn, will
see precipitation chances continue to decrease along with some
clearing skies. Temperatures will also rebound upward on Saturday,
though forecast high marks remain below seasonal normal for this
time of year.

Model guidance shows the shortwave ridge quickly giving way to a
subtle embedded impulse Saturday night into early Sunday.
Consensus amongst guidance is that despite an increase in
moisture, precipitation chances remain fairly low with this
feature, and rather we're more likely to see another increase to
cloud cover across the region.

.LONG TERM (After 12Z/6AM Sunday)...A relatively quiet long term
period is expected as guidance doesn't indicate any sort of
significant ridge or trough features appearing through the end of
next week. The best chance for precipitation will be late Monday as
a trough grazes northern Utah and SW Wyoming. Ensemble mean QPF
totals are generally <0.1" fore areas across the northern CWA.

Southwesterly flow will start to re-establish after this trough
pushes to the east. This will allow temperatures to warm 5-10
degrees above normal. Moisture will remain across the region which
will keep orographic convection possible, particularly across
northern Utah, each afternoon. Additionally, diurnal wind gusts will
increase throughout the week, particularly across the southern half
of the CWA, as a trough in the PNW gets closer to the Great Basin.
Less than half of the ensemble members have this trough moving close
enough to northern Utah to produce precipitation for the northern
half of the area. The remaining members keep this trough too far
north to provide much in the way of precipitation.

&&

.AVIATION...KSLC...Mostly dry conditions with lowered CIGs creating
mountain obscuration will prevail through mid morning. There is <25%
chance of showers impacting the terminal throughout the day that
could create some gusty and variable winds along with brief MVFR
conditions. Otherwise, winds will primarily be out of the north
throughout the period.

.REST OF UTAH AND SOUTHWEST WYOMING...Widely scattered rain and snow
showers will continue on and off throughout the day creating
intermittent and brief MVFR/IFR conditions. CIGs will remain
lowered, resulting in mountain obscuration. Fog will be possible
through mid morning across areas near the Idaho border, resulting in
IFR/LIFR conditions. Winds will primarily be northerly with some
variable winds associated with showery activity.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 9 PM MDT this evening for UTZ117.

     Winter Weather Advisory until midnight MDT tonight for UTZ125.

WY...None.
&&

Warthen/Mahan

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