988
FXUS65 KSLC 181018
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
418 AM MDT Thu Jul 18 2024

.SYNOPSIS...High pressure will persist across the region for the
next week. Very hot temperatures are expected to increase the risk
of heat-related illness across lower Washington County and Zion
National Park this weekend.

&&

.SHORT TERM (Through 12Z Saturday)...A higher threat of flash
flooding is expected today, especially across southern Utah. Early
morning upper air and satellite analysis indicates an upper level
ridge centered near the 4-Corners region. As per usual, several
shortwaves are rotating around the western periphery of this
ridge.

PWs have increased over the last 12 hours or so as the position of
the ridge moved into a better position for moisture advection, not
above 1" in the St. George area. By this evening, the 1" contour
should include much of the lower elevations of southern and
western.

Looking at the trends in CAMS for SBCAPE this afternoon and
evening, now expect SBCAPE values around 500-1000 J/kg across much
of the state. While deep layer shear will be less than 20 kts,
given deep moisture and sufficient instability, along with slow
storm motions, the threat of flash flooding will be elevated today
across southern Utah.

Friday looks like somewhat of a repeat, with the threat of flash
flooding persisting across southern Utah.

.LONG TERM (After 12Z Saturday)...Much of the long-term period
will feature a highly-amplified ridge just to our west, remaining
largely unchanged until the arrival of a PacNW trough that may
begin to flatten the ridge heading into mid-week.

Overall, southern Utah can expect daily afternoon showers and
thunderstorms developing due to persistent mid-level moisture.
While highest across the south, these precipitation chances expand
into central UT and even up into the Uinta Mtns. Currently, the
low levels are looking quite dry, thus gusty microburst winds are
the main threat, in addition to an isolated flash flood threat.
Moisture will gradually increase through the work week, thus we`ll
have to keep an eye on that flash flood threat heading into mid-
week.

Temperatures will remain fairly consistent, around 5 degrees
above normal. One area to watch for heat concerns is far
southwestern UT, which, although only a few degrees warmer on
Saturday than previous days, may struggle with continued lack of
overnight relief with lows in the low-80s.

Finally, regarding that PacNW trough next week...this is unlikely
to have any sensible impacts in the long-term period, though we
may start to see more of an increase in moisture and slight
decrease in temperatures late in the work week.

&&

.AVIATION...KSLC...Southeasterly winds are likely to transition
to northwesterly around 18-19z, but may become variable and gusty
during the afternoon near any showers. Confidence is low regarding
an exact direction after 20z, when showers and thunderstorms
begin to develop. There is currently a 25% chance that
thunderstorms move over the terminal between 20-04z.

.REST OF UTAH AND SOUTHWEST WYOMING...Widely scattered showers
and thunderstorms are expected to develop after 18z, with the
highest coverage across southern UT and across higher terrain.
These showers may cause periods of heavy rain, MVFR VIS, and gusty
and erratic outflow winds.

&&

.FIRE WEATHER...As moisture increases today into Friday, showers
and thunderstorms will be likely, especially across central and
southern Utah. Heavy rain and wetting rains are most likely south
of I-70. Daily shower and thunderstorms can be expected through
midweek next week, especially across central and southern Utah.

Humidity trends will see minimum humidities highest through
Friday; 15-20% for most valleys and 30-40% for most mountain
areas. By the weekend, these values will fall around 3-5%.
Overnight recoveries will start to trend poorer this weekend for
the valleys especially across northern and western Utah...however
remain good to excellent for the higher terrain.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Excessive Heat Watch from Saturday morning through Sunday
     evening for UTZ123-124.

WY...None.
&&

$$

Kruse/Cunningham

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