Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 901
The Storm Prediction Center issued this mesoscale discussion at Jun 9, 2021, 4:43 PM MDT for Lemhi County, Idaho; 8 counties in Montana. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Jun 9, 2021, 4:43 PM MDT (22:43 UTC)
- Expired
- Jun 9, 2021, 6:15 PM MDT
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Lemhi County, ID, Deer Lodge County, MT, Granite County, MT, Lake County, MT, Lewis and Clark County, MT, Missoula County, MT, Powell County, MT, Ravalli County, MT, Teton County, MT
The radar
The Missoula radar (KMSX), 100 km from the middle of the area, began a volume at 22:48 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
Spokane, WA (KOTX), launched 12:00Z, 10.7 hours before the alert went out and 254 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
- 1475 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km storm-relative helicity
- -34 m²/s²
- 0-3 km storm-relative helicity
- 303 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
568
ACUS11 KWNS 092243
SWOMCD
SPC MCD 092243
MTZ000-IDZ000-100015-
Mesoscale Discussion 0901
NWS Storm Prediction Center Norman OK
0543 PM CDT Wed Jun 09 2021
Areas affected...southwest Montana and northeast Idaho
Concerning...Severe potential...Watch unlikely
Valid 092243Z - 100015Z
Probability of Watch Issuance...20 percent
SUMMARY...An isolated severe threat may develop over the next couple
of hours as storms begin to intensify ahead of a shortwave trough.
Cool temperatures aloft and strong mid-level flow will support a
hail and damaging wind threat with the stronger storms. A watch will
likely not be needed but convective trends will be monitored.
DISCUSSION...Late afternoon satellite imagery showed a western US
trough nudging eastward across portions of the northern and central
Rockies. Recent visible data has shown a general increase in
clusters of towering cumulus within the higher terrain of
northeastern Idaho and southwestern Montana. Destabilization remains
somewhat weak, but south of a differential heating axis, surface obs
indicate dewpoints in the 40s to 50s F are contributing to MUCAPE
around 500 J/kg. As ascent from the approaching trough overspreads
the warming and moistening arimass, additional storm development
appears probable. Strong deep-layer shear 55-65 kts will favor a
discrete storm mode with the potential for hail and damaging wind
gusts. Storms have struggled to become established so far suggesting
coverage may be lower than initially forecast.
..Lyons/Dial.. 06/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TFX...PIH...MSO...BOI...
LAT...LON 45961501 48201412 48471300 48221222 47411213 46711238
45321309 44561407 44301460 44451516 44971540 45271528
45961501SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 8, 6:15 PM MDT | Mesoscale Discussion | SPC | Carter, Custer, Daniels, Dawson, Fallon, McCone and 8 more | 90 min |
| Jun 9, 5:05 PM MDT | Mesoscale Discussion | SPC | Blaine, Cascade, Chouteau, Fergus, Hill, Judith Basin and 2 more | 85 min |
Nearby
Mesoscale Discussions in Montana, 2021Mesoscale Discussions in Idaho, 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.