Alert archive / Utah / Mesoscale Discussions in 2021
Mesoscale Discussion 1811
The Storm Prediction Center issued this mesoscale discussion at Oct 8, 2021, 12:52 PM MDT for 7 counties in Idaho; White Pine County, Nevada; 9 counties in Utah. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 8, 2021, 12:52 PM MDT (18:52 UTC)
- Expired
- Oct 8, 2021, 3:15 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Bannock County, ID, Bear Lake County, ID, Caribou County, ID, Cassia County, ID, Franklin County, ID, Oneida County, ID, Power County, ID, White Pine County, NV, Box Elder County, UT, Cache County, UT, Davis County, UT, Juab County, UT, Morgan County, UT, Rich County, UT, Salt Lake County, UT, Tooele County, UT, Weber County, UT
The radar
The Salt Lake City radar (KMTX), 95 km from the middle of the area, began a volume at 18:51 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
Elko, NV (KLKN), launched 12:00Z, 6.9 hours before the alert went out and 58 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
- 1023 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 181 m²/s²
- 0-3 km storm-relative helicity
- 274 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
641
ACUS11 KWNS 081853
SWOMCD
SPC MCD 081852
UTZ000-IDZ000-NVZ000-082115-
Mesoscale Discussion 1811
NWS Storm Prediction Center Norman OK
0152 PM CDT Fri Oct 08 2021
Areas affected...portions of the northern Great Basin
Concerning...Severe potential...Watch unlikely
Valid 081852Z - 082115Z
Probability of Watch Issuance...5 percent
SUMMARY...Scattered thunderstorm beneath an upper trough may be
capable of producing strong wind gusts or hail this afternoon and
evening. Expected severe coverage will likely remain low enough that
a watch will not be needed.
DISCUSSION...As of 1900 UTC, regional radar and satellite imagery
showed increasing thunderstorm coverage across portions of eastern
NV and western UT. Located beneath a slow moving upper trough across
portions of the Great Basin, these storms are ongoing in a cool but
weakly unstable environment with SPC mesoanalysis showing between
250-500 J/kg of MLCAPE. Regional model soundings show long straight
line hodographs with bulk shear values of 35-50 kts. Despite the
weak buoyancy, the favorable shear may support a few organized
storms including a marginal supercell. Steep low and mid-level lapse
rates from the cold pocket aloft may support a few stronger
downdrafts and some hail potential into this evening.
While uncertainty on the overall severe threat remains large,
additional convective development appears likely over the next
couple of hours in response to increasing forcing for ascent ahead
of the trough and continued diurnal heating. Hi-res guidance shows
scattered storms moving out of eastern NV into northwestern UT and
southern ID late this afternoon and early this evening. Thus the
potential for isolated damaging wind gusts or hail may linger into
the evening before nocturnal inhibition limits the threat after
sunset.
..Lyons/Hart.. 10/08/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SLC...PIH...BOI...LKN...
LAT...LON 39741532 41041533 42101473 42701390 43221243 42731136
41681111 40391179 39801260 39291373 39171459 39741532Nearby
Mesoscale Discussions in Utah, 2021Mesoscale Discussions in Idaho, 2021Mesoscale Discussions in Nevada, 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.