Alert archive / Montana / Mesoscale Discussions in 2017
Mesoscale Discussion 935
The Storm Prediction Center issued this mesoscale discussion at Jun 1, 2017, 12:42 PM MDT for Custer County, Lemhi County, Idaho; 12 counties in Montana. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 1, 2017, 12:42 PM MDT (18:42 UTC)
- Expired
- Jun 1, 2017, 3:15 PM MDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Custer County, ID, Lemhi County, ID, Beaverhead County, MT, Broadwater County, MT, Cascade County, MT, Chouteau County, MT, Deer Lodge County, MT, Granite County, MT, Jefferson County, MT, Lewis and Clark County, MT, Meagher County, MT, Powell County, MT, Silver Bow County, MT, Teton County, MT
The radar
The Missoula radar (KMSX), 137 km from the middle of the area, began a volume at 18:45 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, 6.7 hours before the alert went out and 207 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
- 21 J/kg
- Mixed-layer CIN
- -406 J/kg
- Mixed-layer LCL
- 2141 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 8 m²/s²
- 0-3 km storm-relative helicity
- 128 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
402
ACUS11 KWNS 011843
SWOMCD
SPC MCD 011842
MTZ000-IDZ000-012115-
Mesoscale Discussion 0935
NWS Storm Prediction Center Norman OK
0142 PM CDT Thu Jun 01 2017
Areas affected...north central Idaho and southwest through western
Montana
Concerning...Severe potential...Watch unlikely
Valid 011842Z - 012115Z
Probability of Watch Issuance...20 percent
SUMMARY...Widely scattered thunderstorms are expected to continue
developing through north central Idaho into parts of western
Montana. Some of the storms may become capable of producing isolated
downburst winds and hail this afternoon. Due to the anticipated
sparse coverage of any severe events, a watch is not anticipated.
DISCUSSION...Showers and thunderstorms have begun developing over
the mountains of north central ID into western MT. The combination
of pockets of diabatic warming over the higher terrain and
increasing forcing for ascent through a deep layer downstream from a
progressive shortwave trough will continue to promote
destabilization and thunderstorm development in this region. Latest
objective analysis shows a corridor of 500 J/kg MLCAPE, and the 18Z
special sounding from Great Falls indicates steep 700-500 mb lapse
rates and inverted-V profiles evolving in the sfc-600 mb layer.
Moreover, a belt of moderate winds aloft is overspreading this
region in association with the approaching upper trough. This
environment will promote a threat for isolated downburst winds as
storms intensify this afternoon. Due to limited instability and
expected sparse coverage of the more intense storms, a WW will
probably not be needed.
..Dial.. 06/01/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TFX...PIH...MSO...
LAT...LON 45541437 47361277 48351182 48531050 47580990 45971126
44881263 44081397 44481481 45541437Nearby
Mesoscale Discussions in Montana, 2017Mesoscale Discussions in Idaho, 2017Every mesoscale discussion in 2017
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.