Alert archive / Montana / Mesoscale Discussions in 2021
Mesoscale Discussion 970
The Storm Prediction Center issued this mesoscale discussion at Jun 14, 2021, 2:27 PM MDT for 23 counties in Montana. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 14, 2021, 2:27 PM MDT (20:27 UTC)
- Expired
- Jun 14, 2021, 4:30 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 23 counties
Broadwater County, MT, Carbon County, MT, Cascade County, MT, Chouteau County, MT, Deer Lodge County, MT, Fergus County, MT, Garfield County, MT, Golden Valley County, MT, Granite County, MT, Jefferson County, MT, Judith Basin County, MT, Lewis and Clark County, MT, Meagher County, MT, Musselshell County, MT, Park County, MT, Petroleum County, MT, Powell County, MT, Stillwater County, MT, Sweet Grass County, MT, Teton County, MT, Treasure County, MT, Wheatland County, MT, Yellowstone County, MT
The radar
The Billings radar (KBLX), 129 km from the middle of the area, began a volume at 20:25 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, 8.5 hours before the alert went out and 106 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
- 13 J/kg
- Mixed-layer CIN
- -695 J/kg
- Mixed-layer LCL
- 2646 m above ground
- 0-6 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- 61 m²/s²
- 0-3 km storm-relative helicity
- 277 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
482
ACUS11 KWNS 142028
SWOMCD
SPC MCD 142027
MTZ000-142230-
Mesoscale Discussion 0970
NWS Storm Prediction Center Norman OK
0327 PM CDT Mon Jun 14 2021
Areas affected...portions of central into northern Montana
Concerning...Severe potential...Watch unlikely
Valid 142027Z - 142230Z
Probability of Watch Issuance...20 percent
SUMMARY...A couple stronger thunderstorms may develop later this
afternoon into the evening. Damaging gusts are expected to be the
primary threat. A WW issuance is not anticipated given the expected
sparse coverage of severe.
DISCUSSION...Visible satellite trends depict increasing CU across
the higher terrain of the Rockies across southern MT. Meridional
mid/upper flow is in place due to an impinging upper trough to the
west. Southeasterly surface flow is advecting 50 F dewpoints into
central MT, contributing to the gradual erosion of convective
inhibition and boosting instability (500-1000 J/kg MLCAPE per 20Z
mesoanalysis). Isolated thunderstorms are expected to gradually
develop and intensify through the afternoon/early evening. Veering
in the sfc-500 mb layer is promoting 30 kts of effective bulk shear
and the potential for some updrafts to become somewhat organized
atop a deep, dry boundary layer.
8.5-9.5 C/km surface-500 mb lapse rates are present across much of
central and northern Montana. While flow aloft is overall weak,
microphysical cooling may compensate via downward momentum transport
in the deep sub-cloud layer to support a few strong to potentially
damaging gusts. Any of the more established updrafts may also
produce a brief instance or two of large hail given the depth of the
steep lapse rates. Nonetheless, with very warm low-level
temperatures and a 4000+ m AGL freezing level, most hail that falls
is expected to be small. Overall, the severe threat is expected to
be sparse, and a WW issuance is not expected.
..Squitieri/Grams.. 06/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BYZ...GGW...TFX...MSO...
LAT...LON 46491387 47391321 48191235 48451055 48340909 47920767
47650717 47230690 46640677 46270685 45680740 45340772
45120829 45250959 45561114 46021317 46491387Nearby
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.