Area Forecast Discussion
Issued by NWS Salt Lake City, UT
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152
FXUS65 KSLC 091932
AFDSLC
Area Forecast Discussion
National Weather Service Salt Lake City UT
132 PM MDT Fri Oct 9 2026
.KEY MESSAGES...
- Widespread heavy rainfall is expected to occur across the entirety
of the forecast area starting Saturday afternoon/evening as Tropical
Storm Rachel transitions to an extratropical system to our southwest
and interacts with a strong midlevel trough. Widespread rainfall
amounts from 2-4" are expected across much of the forecast area,
with localized amounts potentially reaching 6-8" across locations
such as higher terrain locations across southwest Utah, the Book
Cliffs, and locations within and adjacent to the Bear River Range.
- A wind threat is expected to accompany this system as it begins to
take on extratropical characteristics. Initially, advisory level
winds will begin to develop across most Utah valley locations
starting just after midnight tonight, becoming more widespread
Saturday afternoon. Advisory level winds are forecast to remain in
place through at least Monday afternoon.
- A more notable high wind threat looks to develop across the
valleys and high terrain of southwest Utah as the potential
development of a sting jet looks to occur Sunday. This would bring
widespread lower elevation winds in excess of 40mph with high
terrain and ridgelines seeing gusts potentially exceed 70mph.
- The potential for severe weather exists across southern and
eastern Utah Sunday into Monday morning. The primary threat will be
severe thunderstorm gusts, though a couple brief tornadoes cannot be
ruled out if discrete convection is realized.
&&
.DISCUSSION... Currently, broad westerly flow aloft is yielding
pleasant conditions across much of the forecast area ahead of
Tropical Storm Rachel. This evening, a deep mid-level trough will
begin to slide southeast toward the Great Basin with mid-level flow
increasing out of the southwest. Additionally, the pressure gradient
is forecast to continually tighten overnight increasing winds
further. As such, winds will begin to gradually mix to the surface
overnight resulting in downslope winds along southwesterly flow
favored terrain (such as the Oquirrhs) across northern UT. Into the
morning and early afternoon hours, we will continue to see more
widespread mixing to the surface, with most valley locations west of
and along I-15 seeing gusts through much of the day in excess of
30mph out of the southwest.
Through much of tomorrow, moisture associated with Tropical Storm
Rachel will gradually push ahead of the main system as the
aforementioned trough slowly moves southeast. With strong ascent in
place as the trough moves in, widely scattered showers and
thunderstorms are expected to develop along and east of I-15 in the
afternoon hours. As ascent continues to strengthen into the evening,
lower elevation locations will begin to see more showers and
thunderstorms overnight, particularly along a strengthening frontal
boundary across northern Utah. This may be the onset of a
Predecessor Rainfall Event (PRE), serving to saturate soils markedly
ahead of the main rainfall event later on in the forecast period. A
PRE is when moisture advects well ahead of the main storm (in this
case, Rachel), and interacting with a frontal boundary producing
heavy rainfall well ahead of the storm. The potential for flash
flooding will gradually increase across southwest Utah later
Saturday evening as more robust moisture pushes north overnight.
Additionally, some severe threat may develop, though would largely
be limited to far southern Utah as instability profiles leave much
to be desired.
On Sunday, numerous hazards are expected to develop across much of
the state with heavy rainfall continuing across the entirety of
Utah, strong winds developing across southwest Utah, and a severe
threat across southwest Utah. The midlevel trough will continue to
gradually deepen as it progresses southeast with Tropical Storm
Rachel pushing inland and phasing into the mean flow, becoming
extratropical with time. Flooding is expected to be a major concern
through the period with widespread 2-4" of rain in the forecast
across much of the state associated with deep tropical moisture.
With recent burn scars such as Forsyth, Cottonwood, Widemouth 2,
Silver King, and more, flash flooding is a concern primarily across
the southern 2/3rds of Utah where the potential for heavier rainfall
amounts appear likely. Additionally, southwesterly flow upslope
favored terrain such as higher terrain across southwest Utah and the
Book Cliffs yield some concern where heavily localized amounts could
potentially reach as high as 6-8" with this event. Location remains
extremely uncertain regarding highest precipitation amounts, but
given the anomalous moisture and forcing in place, these amounts may
be realized. Along the northern 1/3rd of Utah where the potential
PRE may occur followed by persistent moderate rainfall, widespread
areal flooding concerns continue to rise given the large rainfall
totals expected. This is particularly interesting across the Bear
River Range and areas adjacent, where precipitation totals through
the event may also reach 6-8", aided by the PRE. Rainfall is
expected to continue through Tuesday across both locations, with an
attendant flooding/flash flooding threat each day.
The second threat to develop Sunday afternoon is the potential for
strong wind gusts across southwestern Utah. As Tropical Storm Rachel
transitions to an extratropical system, it will begin to broaden in
size and expand its wind field as well as strengthening aloft.
Additionally, hi-res guidance hints at drying occurring in the
midlevels where winds look to strengthen the most. This may indicate
the potential for the development of a sting jet, which would
translate strong wind gusts to the surface in excess of 40-50mph,
with ridgelines potentially seeing gusts in excess of 70mph. This
solution would be particularly concerning given heavy rainfall
totals resulting in saturated soils which may result in a locally
widespread tree blowdown event. As such, a high wind watch has been
issued for portions of southwestern Utah.
Lastly, a severe weather threat looks to develop primarily across
southern Utah and potentially east-central Utah. This setup remains
largely conditional on cloud breaks occurring in order to support
destabilization, though multiple CAM suites hint at this with CAPE
values reaching 1000-1500J/kg across much of the area in question.
In the afternoon hours, a strong shortwave impulse (the main
remnants of Tropical Storm Rachel) will eject northeast as it begins
to phase into the mean flow. Midlevel winds in excess of 60-70kts
with strong surface winds will yield large, looping hodographs
across much of southern Utah with effective shear values ranging
from 40-60kts. Additionally, a few pieces of guidance continue to
indicate the presence of drier air in the midlevels which would
support more isolated convection developing rather than a persistent
stratiform rainfall event, with some concern for the development of
low topped supercells across southern Utah in the afternoon hours.
The drier air pushing in will assist with increasing DCAPE values to
over 1000J/kg, and with strong gradient winds ongoing at the time,
will yield a convectively enhanced downburst threat with these
storms. A conditional threat for a couple tornadoes exists as well
given the shear and instability in place, though some caveats to
this exist. In particular, the tornado threat is heavily dependent
on afternoon clearing in order to preserve lapse rates greater than
7C/km. Additionally, with the potential for highly sheared low-
topped supercells, or "mini spinnies", there is potential that the
higher DCAPE may result in RFD winds shredding the storm apart
leading toward a more pronounced wind threat. However, storm-
relative flow to around 30-40kts may assist with balancing the
inflow/RFD with these storms, which may result in a couple
tornadoes, potentially brief in nature. Terrain interactions may
also assist this process as well, though locations regarding this
are highly uncertain.
Come Monday, the remnants of Rachel will continue ejecting northeast
away from Utah as it continues to phase into the mid-level trough.
The midlevel trough will meander across the Great Basin through at
least Tuesday providing ample ascent with moisture remaining in
place bringing even more rainfall to the area. This may result in an
extension of any Flood/Flash Flood products issued shortly.
Additionally, this will keep the wind threat in place throughout
Monday across much of the state.
Come Wednesday, the mid-level trough will push east with a cold
front sweeping across the forecast area ushering in cooler
temperatures statewide. With this frontal boundary pushing through
and moisture remaining in place, high elevation snow is expected
across primarily northern Utah. Amounts are not forecast to be high
given snow ratios on the order of 4:1, but hopefully this is a good
sign for the winter season moving forward. Lastly, this frontal
passage will bring temperatures statewide to near-normal
temperatures for this time of year.
&&
.AVIATION...
KSLC...VFR conditions will continue at the KSLC terminal through the
TAF period. Winds are expected to remain southerly through the day
today, although there is a 15 percent chance of a brief shift to
northwest within the 21-00z timeframe. A few high-based showers and
thunderstorms may develop in the vicinity of the terminal after 21Z
with some increase in coverage in the overnight hours.
REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will prevail
across all regional terminals through the TAF period. Diurnal winds
this morning will trend more southerly this afternoon. Isolated
showers and thunderstorms will develop over the higher terrain this
afternoon, with more focus on northern Utah overnight. These storms
could bring some gusty and erratic winds, lightning, and brief
mountain obscurations.
&&
.FIRE WEATHER...Ahead of Tropical Storm Rachel, a system will begin
to push southeast with widespread gusty winds developing this
evening through early next week. Through this weekend, widespread
wetting rain is expected across the entirety of the state as the
remnants of Rachel move into the area. Following Rachels
departure, a cool and dry pattern is forecast to develop around
midweek next week.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from 3 AM Saturday to 6 AM MDT Sunday for
UTZ101>109-115-116-118-119-122-126-127.
Flood Watch from late Saturday night through Monday afternoon
for UTZ101>112-114-115.
Flood Watch from Saturday afternoon through Monday afternoon for
UTZ113-116>131.
High Wind Watch from Sunday morning through late Sunday night
for UTZ115>117-119-122-125>127.
WY...None.
&&
$$
PUBLIC...Worster
AVIATION...Mahan
FIRE WEATHER...Worster
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity