Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 904
The Storm Prediction Center issued this mesoscale discussion at Jun 9, 2021, 8:34 PM MDT for 7 counties in Montana. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Jun 9, 2021, 8:34 PM MDT (02:34 UTC)
- Expired
- Jun 9, 2021, 10:00 PM MDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 250
Counties Blaine County, MT, Chouteau County, MT, Fergus County, MT, Hill County, MT, Judith Basin County, MT, Petroleum County, MT, Phillips County, MT
The radar
The Great Falls radar (KTFX), 174 km from the middle of the area, began a volume at 02:33 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 00:00Z, 2.6 hours before the alert went out and 125 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
- 22 J/kg
- Mixed-layer CIN
- -195 J/kg
- Mixed-layer LCL
- 1287 m above ground
- 0-6 km bulk shear
- 71 kt
- 0-1 km storm-relative helicity
- 12 m²/s²
- 0-3 km storm-relative helicity
- 408 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.1
The text
As transmitted.
407
ACUS11 KWNS 100234
SWOMCD
SPC MCD 100234
MTZ000-100400-
Mesoscale Discussion 0904
NWS Storm Prediction Center Norman OK
0934 PM CDT Wed Jun 09 2021
Areas affected...North-central MT
Concerning...Severe Thunderstorm Watch 250...
Valid 100234Z - 100400Z
The severe weather threat for Severe Thunderstorm Watch 250
continues.
SUMMARY...The threat for isolated large hail and damaging wind may
continue into the late evening. Some threat may spread downstream of
WW 250 in the short term.
DISCUSSION...At 0230Z, a long-lived supercell is ongoing across
Phillips County MT, where it earlier produced 3-inch diameter hail.
Trends in visible satellite and objective mesoanalysis suggest that
MLCINH is increasing downstream, so the longevity of this cell is
uncertain. However, given the well-organized nature of the storm and
still-favorable MUCAPE and effective shear, some threat may spread
downstream of WW 250 into Valley County, MT in the short term.
Further west, convection has occasionally pulsed up to near severe
limits, though individual cells have struggled to remain organized.
While MLCINH may be too prohibitive for surface-based storms in that
area, persistent large-scale ascent and favorable instability may
allow for occasionally organized clusters or perhaps an elevated
supercell, with a continued threat for hail and perhaps an isolated
strong wind gust.
..Dean.. 06/10/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GGW...TFX...
LAT...LON 48971054 49030909 48940823 48660707 47580723 46920832
46781048 47091090 48751065 48971054SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 9, 6:42 PM MDT | Severe Thunderstorm Watch | SPC | Blaine, Chouteau, Fergus, Hill, Judith Basin, Petroleum and 1 more | 5 hr |
| Jun 9, 10:51 PM MDT | Mesoscale Discussion | SPC | Blaine, Fergus, Petroleum, Phillips | 84 min |
| Jun 10, 1:47 PM MDT | Mesoscale Discussion | SPC | Blaine, Fergus, Golden Valley, Musselshell, Petroleum, Phillips and 4 more | 88 min |
| Jun 10, 1:56 PM MDT | Mesoscale Discussion | SPC | Daniels, Richland, Roosevelt, Sheridan, Valley, Wibaux | 94 min |
| Jun 10, 2:30 PM MDT | Tornado Watch | SPC | Daniels, Richland, Roosevelt, Sheridan, Wibaux | 6 hr |
| Jun 10, 2:51 PM MDT | Mesoscale Discussion | SPC | Carter | 114 min |
| Jun 10, 2:52 PM MDT | Severe Thunderstorm Watch | SPC | Blaine, Custer, Dawson, Fergus, Garfield, Golden Valley and 7 more | 6 hr |
| Jun 10, 4:36 PM MDT | Mesoscale Discussion | SPC | Fallon, Richland, Roosevelt, Sheridan, Wibaux | 114 min |
| Jun 10, 4:48 PM MDT | Mesoscale Discussion | SPC | Garfield, Golden Valley, Musselshell, Petroleum, Phillips, Treasure and 2 more | 87 min |
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.