Alert archive / Montana / Mesoscale Discussions in 2017

Mesoscale Discussion 973

June 8, 20174 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jun 8, 2017, 9:12 PM MDT for 4 counties in Montana. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Jun 8, 2017, 9:12 PM MDT (03:12 UTC)
Expired: Jun 8, 2017, 10:45 PM MDT
In force: 93 min
Issued by: the Storm Prediction Center

Counties Blaine County, MT, Chouteau County, MT, Fergus County, MT, Hill County, MT

The radar

The Great Falls radar (KTFX), 135 km from the middle of the area, began a volume at 03:16 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, 3.2 hours before the alert went out and 79 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 568 J/kg
Mixed-layer CIN: -34 J/kg
Mixed-layer LCL: 3116 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 65 m²/s²
0-3 km storm-relative helicity: 109 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.2

Open this sounding in Storm Lab

The text

As transmitted.

352 
ACUS11 KWNS 090313
SWOMCD
SPC MCD 090312 
MTZ000-090445-

Mesoscale Discussion 0973
NWS Storm Prediction Center Norman OK
1012 PM CDT Thu Jun 08 2017

Areas affected...Portions of northern Montana

Concerning...Severe Thunderstorm Watch 307...

Valid 090312Z - 090445Z

The severe weather threat for Severe Thunderstorm Watch 307
continues.

SUMMARY...While some threat of gusty winds and marginally severe
hail remains, the overall severe threat should continue to diminish
this evening.

DISCUSSION...Driven by a powerful cold pool (e.g., wind damage and a
significant severe gust reported along I-15 earlier), convection has
lifted northeast across Watch 307 this evening. This trend should
continue into the late evening, with the strongest cells likely
pushing into southern Alberta/Saskatchewan over the next hour or so.
Nonetheless, large temperature/dew point spreads ahead of the
surging outflow imply that the boundary layer remains favorable for
occasional gusty, locally damaging winds across far northeastern
portions of the watch. 

Additionally, a few stronger cells have developed over Judith Basin
and Fergus counties this evening, with occasional 9km CAPPI cores
upwards of 50 dBZ. Residual steep mid-level lapse rates and the
continued influence of an approaching shortwave trough are likely
sufficient for the maintenance of these cells. While adequate
mid-level buoyancy profiles and vigorous southwesterly flow aloft
may provide a brief opportunity for strong winds and marginally
severe hail, increasing convective inhibition will likely temper the
overall threat. Therefore, new watch issuance is not expected.

..Picca.. 06/09/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BYZ...GGW...TFX...

LAT...LON   46950973 48171105 49041097 49080872 48090854 46880900
            46740927 46950973

Nearby

Mesoscale Discussions in Montana, 2017 Every 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.