Alert archive / Utah / Mesoscale Discussions in 2021
Mesoscale Discussion 1552
The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2021, 11:34 AM MDT for 14 counties in Utah. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Aug 18, 2021, 11:34 AM MDT (17:34 UTC)
- Expired
- Aug 18, 2021, 1:00 PM MDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
Counties Beaver County, UT, Carbon County, UT, Duchesne 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), 170 km from the middle of the area, began a volume at 17:36 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Salt Lake City I, UT (KSLC), launched 12:00Z, 5.6 hours before the alert went out and 212 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
- 7 J/kg
- Mixed-layer CIN
- -398 J/kg
- Mixed-layer LCL
- 1192 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- -6 m²/s²
- 0-3 km storm-relative helicity
- 17 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
706
ACUS11 KWNS 181735
SWOMCD
SPC MCD 181734
UTZ000-NVZ000-181900-
Mesoscale Discussion 1552
NWS Storm Prediction Center Norman OK
1234 PM CDT Wed Aug 18 2021
Areas affected...Western to central Utah
Concerning...Severe potential...Watch likely
Valid 181734Z - 181900Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorm coverage is expected to increase across
western to central Utah through the afternoon hours. Severe wind
gusts and perhaps isolated hail will be possible. A watch is likely
soon to address this concern.
DISCUSSION...Latest IR imagery shows deepening convection across
northern UT along and ahead of a cold front as well as developing
storms across southern portions of the state forced via orographic
ascent. Unusually high low-level moisture across the state (denoted
by dewpoints in the mid 50s to low 60s in a few locations) is
supporting 500-1000 J/kg MLCAPE. Instability will continue to
increase as diurnal heating warms temperatures into the upper 80s
this afternoon. Additionally, strong flow aloft associated with the
leading edge of an upper-level wave to the west is supporting
effective bulk shear values on the order of 35-45 knots. Deep-layer
shear and mean flow vectors are roughly oriented along the
initiating cold front, which will likely support clusters and linear
segments capable of an organized wind threat - especially where
boundary-layer lapse rates are greater than 6-7 C/km. Storms
developing off the terrain ahead of the front may develop
supercellular characteristics and pose both a wind and hail threat.
Given the relatively strong forcing for ascent and favorable
environment, a watch is likely soon to address this concern.
..Moore/Dial.. 08/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GJT...SLC...VEF...LKN...
LAT...LON 38761429 39471330 40411203 40541096 40090999 39460959
38690968 38011038 37401133 37321212 37611373 38761429SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 12:14 PM MDT | Severe Thunderstorm Watch | SPC | Beaver, Carbon, Daggett, Duchesne, Emery, Garfield and 15 more | 8 hr |
| Aug 18, 2:35 PM MDT | Mesoscale Discussion | SPC | Beaver, Emery, Garfield, Grand, Iron, Piute and 3 more | 115 min |
Nearby
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.