Clyde, Utah Weather Forecast Discussion

636
FXUS65 KSLC 182126
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
326 PM MDT Thu Sep 18 2025
.SYNOPSIS...Moisture begins to return to the forecast area this
evening with gusty showers across southwest UT this evening.
Chances for showers and thunderstorms across the state increase
through the weekend before a drying trend takes hold once again
early next week.
&&
.SHORT TERM (Through 12Z/6AM Saturday)...Currently, our persistent
upper low has officially cleared the area and is phasing into the
mean upper flow over the far northern plains / northern high plains.
In its wake, a shortwave ridge is building in over UT and southwest
WY with tropical moisture phasing into a shortwave trough over
southern CA. This shortwave trough is forecast to slide northeast
while gradually eroding the ridge over the forecast area to the
southeast somewhat resulting in enhanced moisture transport over the
forecast area and providing enough ascent for scattered showers and
thunderstorms across the forecast area this weekend.
Analyzed PWATs per mesoanalysis across the state sit around roughly
0.5" of water or less as the ridge sits overhead. However, robust
moisture is being observed across southern NV which is expected to
advect north throughout today and this evening into southern UT. An
initial push of moisture is expected following 6pm this evening
across far southwestern UT which may result in scattered dry
thunderstorms capable of gusty winds. While moisture quality is
expected to diminish with northeastern extent, PWATs in excess of
around 1" are expected to overspread southern UT by 12z (6am)
Friday. Hi-res guidance also indicates that some localized PWATs may
be in excess of around 1.2-1.3" across far southwestern UT,
particularly across lower Washington county.
This parameter space may raise some eyebrows, though there are two
factors working against it. First, ascent appears broad and weak
which may result in storms struggling to become more robust and
sustained for a longer time. Second, the morning hours seem more
conducive toward a flooding rain threat across southern UT as it
appears to possess the most favorable overlap of stronger ascent
with the initial push of deeper moisture. Cloud cover is expected to
diminish in the afternoon hours, with guidance indicating that a
good amount of the moisture will begin to mix out. This would not be
nearly as favorable for heavy rainfall given weaker ascent. However,
terrain driven storms remain possible later on in the afternoon with
locally heavier rainfall possible.
Further north across central UT in the afternoon hours, storms may
form across the higher terrain across central UT and across the West
Desert as moisture continues to surge north. Given the lower levels
are expected to remain relatively dry, gusty and erratic winds
appear possible with any storm that develops across the area. These
storms are expected to weaken as sunset draws near with mostly
isolated showers scattered across the forecast area during the
overnight hours.
.LONG TERM (After 12Z/6AM Saturday), Issued 348 AM MDT...
Above-normal moisture will be
in place at the start of the long-term period, reaching up to 200%
of normal across western Utah (150% across eastern Utah/southwest
Wyoming). Mid-level flow will be largely zonal on Saturday, though
weak synoptic dynamics from a 80-90kt jet streak and subtle
shortwave trough will help scattered showers and thunderstorms to
develop across the forecast area by Saturday afternoon. Despite
appreciable column moisture, model soundings actually suggest that
drier air will move into the mid levels across the state,
potentially limiting convective development and flash flood
potential. By Sunday, this trend will continue, with most convection
expected across northern Utah and primarily over higher terrain
given an overall lack of synoptic lift.
By late Sunday, a grazing trough will advect much drier air into the
region, with PWATs dipping down to 50% of normal by late Monday.
Interestingly, there are still roughly 20% of ensemble members that
actually favor a stronger trough overhead instead of just grazing
our area; this could produce cooler and wetter conditions to start
the work week, if this scenario were to pan out. High pressure will
then build over Utah behind this trough, though forecast confidence
decreases significantly after Tuesday. Models can agree on the
development of a cutoff low over SoCal, but they diverge greatly
with regards to where/when this low moves by mid-week. Ultimately,
this will impact how long high pressure resides over our area. By
Day 7/Thursday, now 61% of ensemble members favor high pressure
still overhead, with or without an strong upstream trough. Another
23% favor a weak trough, while the remaining 16% are still hanging
onto a potent trough over the western US...lower than where chances
were yesterday.
&&
.AVIATION...KSLC...VFR conditions will persist for the KSLC
terminal through the period. Dry conditions will continue with some
increasing mid level clouds. Winds will remain light and diurnally
driven.
.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will persist
for the entire airspace through the period. Dry conditions with
light and diurnally driven winds will continue across the north with
increasing mid level clouds. Across the south moisture will increase
with a mix of stratiform precipitation and isolated convection
overnight. Winds across the south will be light and diurnally driven
aside from gusty erratic winds associated with any convection
overnight.
&&
.FIRE WEATHER...High pressure is expected to gradually slide east
this evening as moisture begins to push into UT via persistent
southwesterly winds through the weekend increasing humidities across
the state. Dry thunderstorms appear possible with the initial
moisture surge this evening across far southwestern UT ahead of
better moisture. Coverage for showers and thunderstorms see an
increase tomorrow with better moisture moving in across southern and
central UT featuring the best chance for a wetting rain over the
next few days. On Saturday and Sunday, chances for showers and
thunderstorms shift to northern UT before another drying trend takes
hold on Monday.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Worster
LONG TERM...Cunningham
AVIATION...Mahan
FIRE WEATHER...Worster
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

NWS SLC Office Area Forecast Discussion