Alert archive / Utah / Mesoscale Discussions in 2021
Mesoscale Discussion 1545
The Storm Prediction Center issued this mesoscale discussion at Aug 17, 2021, 12:49 PM MDT for 13 counties in Utah. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Aug 17, 2021, 12:49 PM MDT (18:49 UTC)
- Expired
- Aug 17, 2021, 2:45 PM MDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Beaver County, UT, Carbon County, UT, Emery County, UT, Garfield County, UT, Iron County, UT, Juab County, UT, Millard County, UT, Piute County, UT, Sanpete County, UT, Sevier County, UT, Utah County, UT, Wasatch County, UT, Wayne County, UT
The radar
The Cedar City radar (KICX), 148 km from the middle of the area, began a volume at 18:48 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Salt Lake City I, UT (KSLC), launched 12:00Z, 6.8 hours before the alert went out and 218 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 3488 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 8 m²/s²
- 0-3 km storm-relative helicity
- 26 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
030
ACUS11 KWNS 171850
SWOMCD
SPC MCD 171849
UTZ000-NVZ000-172045-
Mesoscale Discussion 1545
NWS Storm Prediction Center Norman OK
0149 PM CDT Tue Aug 17 2021
Areas affected...Central to Western Utah
Concerning...Severe potential...Watch possible
Valid 171849Z - 172045Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorms are expected to increase in coverage through
the mid to late afternoon hours. Increasing instability and hot
surface temperatures will support the potential for severe downburst
winds. A watch is possible in the coming hours to address this
concern.
DISCUSSION...Latest surface observations across UT show temperatures
climbing into the mid to upper 80s with a slight increase in
dewpoints for some locations thanks to modest low-level moisture
advection from AZ. This is allowing MUCAPE values to increase well
above 1000 J/kg from southwest to central UT. This is priming the
thermodynamic environment for thunderstorm development through the
mid to late afternoon hours as an upper-level wave and attendant
surface trough push into the region from the west. Growing cumulus
fields across eastern NV and west/central UT and a few transient
thunderstorms have been noted over the past 1-2 hours, and are
further evidence of destabilization. Boundary-layer mixing is
forecast to deepen substantially as temperatures warm into the low
90s due to an elevated mixed layer noted in the 12z SLC sounding.
This will allow for efficient downward mixing and evaporative
cooling conducive to severe downburst winds with any strong
thunderstorm. Convective coverage may increase gradually through a
combination of orographic ascent and more focused lift along the
surface trough/ahead of the upper-level wave, but coverage may be
sufficient to warrant a severe thunderstorm watch in the coming
hours.
..Moore/Hart.. 08/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SLC...VEF...LKN...
LAT...LON 38721454 39741425 40651252 40591154 40271070 39161045
38311079 37671159 37451273 37731401 37941441 38721454Nearby
Mesoscale Discussions in Utah, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.