Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 1612
The Storm Prediction Center issued this mesoscale discussion at Aug 26, 2021, 2:06 PM MDT for 9 counties in Montana. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Aug 26, 2021, 2:06 PM MDT (20:06 UTC)
- Expired
- Aug 26, 2021, 4:00 PM MDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Big Horn County, MT, Fergus County, MT, Garfield County, MT, Golden Valley County, MT, Musselshell County, MT, Petroleum County, MT, Rosebud County, MT, Treasure County, MT, Yellowstone County, MT
The radar
The Billings radar (KBLX), 117 km from the middle of the area, began a volume at 20:08 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
Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 8.1 hours before the alert went out and 187 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
- 1259 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 171 m²/s²
- 0-3 km storm-relative helicity
- 227 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
038
ACUS11 KWNS 262006
SWOMCD
SPC MCD 262006
MTZ000-262200-
Mesoscale Discussion 1612
NWS Storm Prediction Center Norman OK
0306 PM CDT Thu Aug 26 2021
Areas affected...central Montana
Concerning...Severe potential...Watch possible
Valid 262006Z - 262200Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated strong/severe storms including a few supercells
may develop late this afternoons across central Montana. Damaging
winds and hail will be the primary severe risk.
DISCUSSION...Ahead of a mid-level shortwave trough evident from
afternoon WV imagery, deepening cumulus towers were noted along the
eastern edge of the Rockies across central Montana. Here, diurnal
heating and weak upslope flow are supporting gradual destabilization
with 500-1000 J/kg of MLCAPE present according to SPC mesoanalysis.
Mid-level flow associated with the trough is also supporting between
25 and 35 kt of effective shear favorable for organized clusters and
perhaps a few supercell structures. Relatively dry low levels
suggest downdraft and cold pool development will favor a damaging
wind threat with the stronger storms. Cool temperatures aloft
beneath the mid-level trough may also support the potential for
severe hail, especially with any rotating storms.
Storm development and an increase in severe risk appears possible by
22-23z as initial updrafts begin to move off of the the higher
terrain into central Montana. Considerable uncertainty remains on
the magnitude of severe threat as hi-res guidance suggests storm
coverage may be quite limited. Despite the uncertainty, the
CAPE/Shear space would support at least an isolated severe wind/hail
risk with any storms that develop. Convective trends will be
monitored for a possible weather watch.
..Lyons/Dial.. 08/26/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BYZ...GGW...TFX...
LAT...LON 47890892 48070757 47460677 46640623 46060627 45160698
45220817 46410931 47080982 47890892Nearby
Mesoscale Discussions in Montana, 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.