Alert archive / Montana / Mesoscale Discussions in 2017

Mesoscale Discussion 977

June 9, 2017Custer County, Prairie County, Rosebud County, Montana

The Storm Prediction Center issued this mesoscale discussion at Jun 9, 2017, 7:37 PM MDT for Custer County, Prairie County, Rosebud County, Montana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jun 9, 2017, 7:37 PM MDT (01:37 UTC)
Expired: Jun 9, 2017, 10:00 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Custer County, MT, Prairie County, MT, Rosebud County, MT

The radar

The Billings radar (KBLX), 170 km from the middle of the area, began a volume at 01:40 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

Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 1.6 hours before the alert went out and 251 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2931 m above ground
0-6 km bulk shear: 63 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: 31 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

996 
ACUS11 KWNS 100137
SWOMCD
SPC MCD 100137 
MTZ000-100400-

Mesoscale Discussion 0977
NWS Storm Prediction Center Norman OK
0837 PM CDT Fri Jun 09 2017

Areas affected...Southeast MT

Concerning...Severe potential...Watch unlikely 

Valid 100137Z - 100400Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms are likely to increase in coverage and
intensity across southeast MT through the evening hours. Some of the
stronger storms will be capable of severe-caliber wind gusts and
some hail.

DISCUSSION...Thunderstorms have shown signs of intensification early
this evening across southeast MT, particularly near/between
Interstates 90 and 94 from near Hardin to the Forsyth/Rosebud areas
(southwest of Miles City) as of 0130Z. While the boundary layer is
not overly moist or potentially unstable in the presence of lower
40s F surface dewpoints, weak CAPE/steep lapse rates and
strengthening deep-layer southwesterly winds (noted in upstream 00Z
upper-air data) above the surface will support some stronger
updrafts/downdrafts. This may especially be the case as stronger
forcing for ascent currently overspreading eastern ID/southwest
MT/far western WY approaches the region, while low-level upslope
trajectories continue to gradually increase within the post-frontal
environment. 

Any severe risk across southeast MT over the next few hours should
remain relatively localized, although a somewhat more organized
cluster of storms capable of localized severe-caliber winds could
eventually materialize and spread northeastward later this evening.

..Guyer/Weiss.. 06/10/2017

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

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

LAT...LON   45920807 47020500 45920418 45040677 45920807

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.