Alert archive / Utah / Mesoscale Discussions in 2021

Mesoscale Discussion 1684

September 2, 20216 counties in Utah

The Storm Prediction Center issued this mesoscale discussion at Sep 2, 2021, 2:41 PM MDT for 6 counties in Utah. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Sep 2, 2021, 2:41 PM MDT (20:41 UTC)
Expired: Sep 2, 2021, 5:15 PM MDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Box Elder County, UT, Davis County, UT, Morgan County, UT, Salt Lake County, UT, Tooele County, UT, Weber County, UT

The radar

The Salt Lake City radar (KMTX), 58 km from the middle of the area, began a volume at 20:42 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, 8.7 hours before the alert went out and 69 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 268 J/kg
Mixed-layer CIN: -170 J/kg
Mixed-layer LCL: 1693 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 108 m²/s²
0-3 km storm-relative helicity: 101 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

329 
ACUS11 KWNS 022041
SWOMCD
SPC MCD 022041 
UTZ000-IDZ000-022315-

Mesoscale Discussion 1684
NWS Storm Prediction Center Norman OK
0341 PM CDT Thu Sep 02 2021

Areas affected...Northern Utah

Concerning...Severe potential...Watch unlikely 

Valid 022041Z - 022315Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated thunderstorms are expected to develop this
afternoon and early evening across northern Utah, posing a threat
for damaging winds.  The limited coverage of severe thunderstorms
will likely preclude the necessity of a watch.

DISCUSSION...Strong heating in the presence of anomalous low-level
moisture (exceeding 90th percentile values for this date) has
resulted in modest destabilization across the area, characterized by
MLCAPE values around 1000 J/kg per mesoanalysis.  Recent VWPs from
Salt Lake City (MTX) indicate increasing west-southwesterly flow
aloft (~30 knots at 2-km AGL) as the positively tilted trough
approaches from the west.  Consequently, a favored corridor with
overlapping instability and shear is developing across northern
Utah.  

The lack of forcing will likely limit thunderstorm coverage and
severe potential; nevertheless, thunderstorms are trying to develop
in the drier air over the higher terrain of far eastern Nevada and
far western Utah.  As these storms move into a more favorable
thermodynamic environment (including DCAPE over 1200 J/kg) to the
east, they should intensify and organize, posing a threat for
isolated damaging winds.

..Jirak/Grams.. 09/02/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...SLC...PIH...

LAT...LON   40331403 40831402 41241380 41691312 42021236 41761176
            41291153 40771150 40551162 40401171 40081227 39871289
            39841347 40331403

Nearby

Mesoscale Discussions in Utah, 2021 Every 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.