Strong Wind in Utah, May 29, 2025

Area Forecast Discussion
National Weather Service Salt Lake City UT
348 AM MDT Thu May 29 2025

.SYNOPSIS...Temperatures will be on the rise into the weekend as
higher pressure builds in, along with a decreasing trend in daily
shower/thunderstorm chances. Much cooler and wetter conditions are
then likely by early next week, remaining unsettled into the
workweek.

&&

Key Points:

- Scattered showers/thunderstorms today will carry a medium chance
  of breezy outflow winds gusting over 30 mph. Such storms will be
  mostly east of I-15 and tied to higher terrain, with a low chance
  of drifting into the Uinta Basin and Castle County.

- Temperatures will climb to 10-15 degrees above normal by the
  weekend, bringing a very high chance of the first 90 degree day
  of the year for SLC and first 100 for St George.

- A much cooler and wetter pattern will arrive next week. There is
  potentially for significant widespread precipitation, though
  important forecast details have yet to be sorted out.

.SHORT TERM...(Through 12Z/6AM Saturday)...
Satellite and upper-air analysis early this morning reveals a
ridge of high pressure centered over the Great Basin and a closed
low offshore of SoCal. A weak shortwave trough is on the
downstream side of the ridge near the Utah/Wyoming border, and a
deformation axis stretches from the closed low to the Utah/Arizona
border. Light radar returns have been noted overnight with both
features, though given dry surface conditions it is unlikely that
anything is reaching the ground, especially in the lower
elevations. Within the northwest flow aloft and the embedded
shortwave ripple along the UT/WY border mentioned above, PWATs
remain a bit elevated (up to 140% of normal), though soundings
reveals that this is all at mid levels with fairly dry surface
dewpoints (mostly in the 30s).

Generally weak convection is expected to fire again this
afternoon over the higher terrain, with a few hundred J/Kg
instability available per HREF means. The northwest flow
direction will favor areas east of I-15, with some potential of
cells drifting east into the Uinta Basin and Castle Country in the
late afternoon and evening. As has been the case the last few
days, the main threat is gusty outflow winds in the 30-40 mph
range, along with a low lightning threat.

The ridge axis mentioned earlier will continue to approach our
area into Friday, bringing hotter temperatures, subsidence, and a
decreasing amount of mid-level moisture. Thus, cumulus buildups
will become more suppressed Friday with more isolated coverage of
any thunderstorm chances and limited to only the mountains. As
temperatures climb a few degrees, the NBM currently shows a 60%
chance of the first 90 degree day at SLC and a 90% chance of the
first triple digit day for St George (both of which are around a
week ahead of the average over the period of record).

.LONG TERM (After 12Z/6AM Saturday)...Warm and generally dry
weather continues through the weekend as a Rex block remains the
dominant pattern across the western US. The area of high pressure
over the PacNW shifts eastward on Saturday in response to a
downstream shortwave trough, with the ridge axis centering
overhead. Temperatures continue to warm aloft as a result, with H7
temperatures topping out around 14-16C across Utah and southwest
Wyoming. This will result in some of the warmest temperatures of
the year so far across the region, with temperatures in the low-
mid 90s for most valley locations except lower Washington county,
where highs are expected to break the century mark.

The Rex block pattern begins to break down on Sunday, with the
persistent area of low pressure over the Baja Peninsula finally
becoming dislodged before a closed low tracks northeast into the
Desert Southwest late Sunday into Monday. Temperatures aloft cool
significantly across southwestern Utah as a result, with highs
running a few degrees cooler in some locations on Sunday afternoon.
Otherwise, temperatures are expected to remain largely unchanged
across the remainder of the forecast area.

The aforementioned closed low will bring with it an influx of
tropical moisture as it moves into the Desert Southwest, aided by a
decaying tropical system. Chances for precipitation increase as
early as Sunday afternoon mainly across southern Utah, before
becoming more widespread into Monday. PWATs gradually rise to around
0.8-1.0 inches across Utah and southwest Wyoming by early Monday,
indicating increased potential for heavy rains across the region.
The ECMWF Extreme Forecast Index continues to highlight notable
shift-of-tails values across southern Utah, with increased
probability from previous forecast. As such, total QPF on Monday has
increased substantially across the area. This tropical moisture
lingers across the region on Tuesday, allowing for widespread
precipitation to continue before drier air under northwesterly flow
behind this system works its way into the region into Wednesday.

The pattern appears to remain quite progressive Wednesday onward,
keeping temperatures near seasonal averages with additional chances
for precipitation through the remainder of the week.

&&

.AVIATION...KSLC...Winds remain generally light, following diurnal
trends through the remainder of the TAF period. Southeasterly winds
this morning transition northwest this afternoon, though isolated
convection developing again this afternoon off the higher terrain
may lead to periods of variable winds.

.REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions continue for
all regional terminals throughout the TAF period. Another round of
afternoon convection is expected once again today mainly between 18-
02z, but will mostly remain tied to higher terrain. There is a 30%
chance for convection to impact KEVW/KCDC/KBCE this afternoon, with
potential to produce gusty and erratic outflow winds.

.FIRE WEATHER...A grazing system with limited moisture will yield
one more day of isolated to scattered diurnal convection today.
This activity will once again favor high terrain with limited
drifting into adjacent valleys. Gusty erratic outflow winds and
lightning will be possible with this convection with low chances
of wetting rain. A strengthening ridge of high pressure then
becomes the dominant forecast influence Friday on into the
weekend, raising temperatures and causing the daily thunderstorm
chances to trend downward Friday to almost nil by Saturday.

Forecast models continue to advertise a moisture-rich weather
disturbance lifting through the Desert Southwest and into the
Four Corners region late Sunday into Monday, with more widespread
precipitation and wetting rain chances accompanying it. The
forecast pattern evolution then becomes a bit chaotic as a deep
area of low pressure shifts into the Great basin, but in general
the consensus supports a continuation of unsettled conditions
along with cooler temperatures. Wetting rains are likely across
much of the region by Monday and Tuesday, though there is still
some forecast uncertainty as to which areas of the state might be
most favored for more significant precipitation.

&&

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

SHORT TERM...Van Cleave
LONG TERM...Whitlam
AVIATION...Whitlam
FIRE WEATHER...Van Cleave

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