Area Forecast Discussion
Issued by NWS Salt Lake City, UT
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239
FXUS65 KSLC 210017
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
617 PM MDT Mon Jul 20 2026
.KEY MESSAGES, Issued 117 PM MDT Mon Jul 20 2026...
- Scattered showers and thunderstorms are expected to develop across
portions of central, southern, northeast UT, and southwest WY each
afternoon within this forecast as monsoonal moisture continues
making its way north.
- The risk for flash flooding continues across the majority of the
forecast area, highlighted by WPC with a Marginal Risk (1/4) of
exceeding flash flood guidance each day encompassing nearly all of
UT through at least Friday. A Slight Risk (2/4) of exceeding flash
flood guidance exists across the majority of UT Tuesday and
Wednesday afternoon, expanding into southwest WY Wednesday afternoon.
- Hazardous temperatures look to develop across northern UT this
afternoon, particularly along the I-15 corridor and Great Salt Lake
Desert. As such, a heat advisory remains in effect.
&&
.DISCUSSION, Issued 117 PM MDT Mon Jul 20 2026...
Monsoonal moisture remains in place across the
southwest as high pressure meanders over the four corners. Beneath
this ridge, PWATs in excess of 1" continue to push north across most
valley locations this afternoon. Daily chances for showers,
thunderstorms, and potentially flash flooding continue through at
least Friday across much of UT with this pattern in place, expanding
into southwest WY Tuesday and Wednesday. Deeper moisture looks to
advect further north starting Tuesday as some stronger synoptic
forcing moves in from the west, increasing PoPs Tuesday afternoon
bringing heavy rainfall and potentially flash flooding to all of UT
and southwest WY.
Thunderstorm development across central and southern UT will occur
around 1200-1400 this afternoon. PWAT anomalies across southern and
central UT once again range from 0.5-1" of water supporting a heavy
rain threat. However, compared to other days, mid-level moisture has
decreased slightly as dry air has moved into the mid-levels. This
will serve to impact vertical development and overall intensity of
storms this afternoon. Regardless, instability in excess of 1000J/kg
with deep warm cloud layers up to 3km continue to support the
development of efficient rainmakers, though more isolated this
afternoon, with heavy rain expected from well established storms.
One failure mode that may occur today would be the increase in 500mb
flow, assisting storms off the terrain which have otherwise remained
anchored over the past few days. With faster moving storms, heavier
rain rates may be needed in order to produce flash flooding,
yielding some uncertainty with todays forecast given moisture
quality is not as good as previous days keeping the flash flooding
threat more isolated.
As the ridge builds overhead, temperatures this afternoon are
forecast to reach into the upper 90s to low 100s across most valley
locations across northwest UT. This has resulted in widespread
"major" HeatRisk values, primarily within valley locations along the
I-15 corridor and Great Salt Lake Desert, with a few areas reaching
"major". As such, a heat advisory has been issued for the
aforementioned locations.
On Tuesday and Wednesday, moisture return increases with the mid-
levels moistening once again ahead of stronger synoptics further
west. Additionally, moisture is forecast to advect further north
during this time expanding the flash flooding threat to northern UT
on Tuesday, then to southwest WY on Wednesday. Enhanced flow aloft
may hinder the overall flooding threat, though anomalously deep
moisture (PWAT anomalies on the order of 0.5-1") remain in place,
supporting potentially heavy rainmakers. Additionally, some shear
will be in place (0-6km shear on the order of 20-30kts) which will
help storms sustain themselves rather than pulsing and gusting out,
potentially enhancing the flash flood threat. Currently, the WPC has
outlined much of UT on Tuesday and Wednesday in a Slight Risk (2/4)
for exceeding flash flood guidance, with southwest WY outlined in a
Slight Risk on Wednesday.
Some severe potential exists on both Tuesday Wednesday across
northern UT and southwest WY as a few shortwaves traverse the Great
Basin in the afternoon hours. With ample shear (0-6km 20-30kts) with
CAPE from 500-800J/kg, a few longer-lived storms, perhaps a couple
transient supercells, may develop in the afternoon hours each day.
Confidence regarding timing and location of these shortwaves remain
highly uncertain at this time, though the broad synoptic pattern
associated with this would support a potential damaging wind threat
and potentially some small hail if it were to materialize.
&&
.AVIATION...
KSLC...Downsloping easterly wind gusts due to convective activity
over the Wasatch will continue through around 01z before decreasing
and easing back northwesterly through the remainder of the night.
Nocturnal shower activity will result in periods of variable winds
at the terminal between roughly 07-11z tonight, with gusts exceeding
25 kts possible through this period. Winds increase out of the
northwest after 18z, before convective activity developing after 20z
brings more gusty and erratic winds through the remainder of the
afternoon and evening. VFR conditions prevail at the terminal,
though heavier rainfall tomorrow afternoona and evening could result
in brief MVFR conditions.
REST OF UTAH AND SOUTHWEST WYOMING...Convective activity dwindles
through the remainder of the evening. There is a threat for
nocturnal showers and thunderstorms overnight across most of the
airspace, mainly between the 07-12z timeframe; this activity will be
capable of producing variable gusty winds for most regional
terminals overnight. Otherwise, widely scattered showers and
thunderstorms redevelop after around 19z on Tuesday, with MVFR
conditions possible for many terminals through the evening as heavy
rainfall may bring lowered CIGS/VIS at times.
&&
.FIRE WEATHER, Issued 117 PM MDT Mon Jul 20 2026...
Monsoonal moisture remains across UT increasing
humidities while raising chances for showers and thunderstorms
across the state moderating fire weather conditions overall. Chances
for showers and thunderstorms continue to be elevated across central
and southern UT this afternoon, and the Uintas ranging from 50-80%.
A wetting rain remains favored this afternoon across each mentioned
location. Expect showers and thunderstorms to develop along higher
terrain parallel to I-15 each afternoon over the next several days
around 1200-1400 with gusty outflow winds, heavy rainfall, and
lightning. Winds will generally remain light terrain driven /
diurnal over the next several days. Chances for showers and
thunderstorms increase across northern UT starting Tuesday with
notably higher chances across the entirety of UT Tuesday and
Wednesday afternoons.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory until midnight MDT tonight for UTZ101>105.
Flood Watch from Tuesday afternoon through late Tuesday night
for UTZ113-115>131.
WY...None.
&&
$$
PUBLIC...Worster
AVIATION...Whitlam
FIRE WEATHER...Worster
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity
