Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 1189
The Storm Prediction Center issued this mesoscale discussion at Jul 7, 2021, 5:48 PM MDT for 14 counties in Montana. It was in force for 117 min.
The area
The outline as issued.
The facts
- Issued
- Jul 7, 2021, 5:48 PM MDT (23:48 UTC)
- Expired
- Jul 7, 2021, 7:45 PM MDT
- In force
- 117 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 346
Counties Big Horn County, MT, Carbon County, MT, Custer County, MT, Fergus County, MT, Garfield County, MT, Golden Valley County, MT, Musselshell County, MT, Petroleum County, MT, Rosebud County, MT, Stillwater County, MT, Sweet Grass County, MT, Treasure County, MT, Wheatland County, MT, Yellowstone County, MT
The radar
The Billings radar (KBLX), 57 km from the middle of the area, began a volume at 23:48 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
Great_falls, MT (KTFX), launched 12:00Z, 11.8 hours before the alert went out and 235 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
- 42 J/kg
- Mixed-layer CIN
- -360 J/kg
- Mixed-layer LCL
- 2232 m above ground
- 0-6 km bulk shear
- 36 kt
- 0-1 km storm-relative helicity
- -61 m²/s²
- 0-3 km storm-relative helicity
- 70 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
150
ACUS11 KWNS 072349
SWOMCD
SPC MCD 072348
MTZ000-080145-
Mesoscale Discussion 1189
NWS Storm Prediction Center Norman OK
0648 PM CDT Wed Jul 07 2021
Areas affected...Montana
Concerning...Severe Thunderstorm Watch 346...
Valid 072348Z - 080145Z
The severe weather threat for Severe Thunderstorm Watch 346
continues.
SUMMARY...The threat for severe winds continues across WW346 as
storms transverse southern and central Montana.
DISCUSSION...A few broken convective lines continue to move eastward
across southern and central MT with several measured severe gust and
wind damage reports noted over the past hour. Although MLCAPE
remains modest per recent mesoanlysis estimates (upwards of 500
J/kg), mid and upper-level winds remain strong over the region with
60-80 knot westerly winds noted in recent KBLX and KGGW VWP
observations. The strong shear and modest instability will continue
to support loosely organized bands of storms capable of severe winds
at least through 03z and possibly later as diurnal cooling gradually
increases inhibition. The highest wind threat may reside along/ahead
of the intersection of a western band of storms and the outflow from
a leading cluster where lift will be maximized. Storms approaching
eastern portions of WW 346 will encounter better boundary-layer
moisture and slightly decreased MLCIN that may allow the severe risk
to persist into far eastern MT, though radar presentation of the
leading convection has been poor over the past 30 minutes,
introducing uncertainty into this potential. New development is also
noted west of the Glasgow, MT area where the CAPE/shear parameter
space is similar to locations further south, though weaker forcing
for ascent should support more isolated cells (and perhaps a higher
hail threat).
..Moore.. 07/07/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BYZ...GGW...TFX...
LAT...LON 45411042 46401049 47171024 47500919 47390735 47310645
46880585 46290548 45760563 45180621 45090763 45120981
45411042SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 6, 6:40 PM MDT | Mesoscale Discussion | SPC | Blaine, Fergus, Garfield, Hill, Musselshell, Petroleum and 4 more | 95 min |
| Jul 6, 10:27 PM MDT | Mesoscale Discussion | SPC | Custer, Garfield, Phillips, Powder River, Rosebud | 93 min |
| Jul 7, 2:03 PM MDT | Mesoscale Discussion | SPC | Broadwater, Cascade, Custer, Fergus, Garfield, Golden Valley and 13 more | 117 min |
| Jul 7, 3:03 PM MDT | Severe Thunderstorm Watch | SPC | Big Horn, Broadwater, Carbon, Carter, Cascade, Chouteau and 19 more | 8 hr |
Nearby
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.