017
FXUS65 KSLC 200919
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
319 AM MDT Wed Aug 20 2025

.SYNOPSIS...High pressure will bring warm and mostly dry
conditions to the region today. A monsoon surge will bring
moisture into the area for the latter part of the week and into
next week.

&&

.DISCUSSION...An area of high pressure continues to strengthen
across the Four Corners region today, resulting in continued hot
and dry conditions across Utah and southwest Wyoming. Mid-level
moisture creeping up the western periphery of this Four Corners
high will result in PWAT values around 0.7-0.8" across far
northwest Utah and portions of southern and central Utah. These
values are sufficient enough to see some high-based, mainly dry
showers and thunderstorms developing across the high terrain of
the aforementioned those areas this afternoon, which will be
capable of producing gusty and erratic outflow winds. Temperatures
will be similar to those observed yesterday, with highs near 100
degrees across most valley locations including the Wasatch Front.

Monsoonal moisture continues to overspread the region through the
latter half of the week as the Four Corners high persists, keeping
afternoon showers and thunderstorms a daily threat through the
weekend. Deeper moisture advection mainly across southern and
northeastern Utah will lead to a more mixed wet and dry character
of storms on Thursday.

Storms will continue to trend wetter Friday and into the weekend
as PWAT anomalies push upwards of 150-200% of normal. The Weather
Prediction Center continues to highlight southern Utah for a
Marginal (level 1 of 4) risk, or at least 5% chance, for rainfall
to exceed flash flood guidance Friday and Saturday. By Sunday,
nearly the entire state of Utah has been placed under this
Marginal risk for excessive rainfall. Locations with greatest
threats for flash flooding include slot canyons, normally dry
washes, slickrock areas, and recent burn scars.

Despite increasing moisture across southern Utah on Thursday and
Friday, temperatures remain elevated across the area through this
period. High temperatures in the 105 to 109 degree range are
expected each afternoon for lower Washington County and Zion
National Park, resulting in Major to Extreme HeatRisk across these
areas. Overnight lows are not expected to offer much relief, with
temperatures only bottoming out in the high 70s to low 80s. As
such, an Excessive Heat Warning has been hoisted for both Zion and
lower Washington County for Thursday and Friday. We`ll see a
gradual downtrend in temperatures across the region this weekend
and into early next week.

&&

.AVIATION...KSLC...VFR conditions prevail under clear and dry
conditions at the KSLC terminal through the period. Winds are
expected to remain generally light, with southeasterly winds this
morning transitioning to the northwest around 19z.

.REST OF UTAH AND SOUTHWEST WYOMING...Winds remain generally light
and diurnally driven. A few high-based thunderstorms will be
possible across northwestern Utah and the southern Utah mountains.
Gusty and erratic winds will be the main threat.

&&

.FIRE WEATHER...Conditions remain hot and dry today, though increasing
mid-level moisture will lead to the development of isolated high-
based showers and thunderstorms across far northwest and south-
central Utah this afternoon. Dry lightning strikes and gusty,
erratic outflow winds will be the main concern for any
thunderstorms that develop.

Moisture deepens across Utah through the remainder of the week,
with thunderstorms gradually transitioning from mainly dry today
to mainly wet by Friday. Chances for widespread wetting rains
increase mainly across southern Utah through the weekend and into
early next week as monsoonal moisture continues to overspread the
region.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Extreme Heat Warning from noon Thursday to 9 PM MDT Friday for
     UTZ123-124.

WY...None.
&&

$$

Whitlam/Kruse

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