Alert archive / Montana / Mesoscale Discussions in 2014

Mesoscale Discussion 749

May 28, 201423 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at May 28, 2014, 2:12 PM MDT for 23 counties in Montana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 28, 2014, 2:12 PM MDT (20:12 UTC)
Expired: May 28, 2014, 4:15 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 23 counties

Big Horn County, MT, Blaine County, MT, Broadwater County, MT, Carbon County, MT, Cascade County, MT, Chouteau County, MT, Fergus County, MT, Gallatin County, MT, Golden Valley County, MT, Hill County, MT, Jefferson County, MT, Judith Basin County, MT, Liberty County, MT, Madison County, MT, Meagher County, MT, Musselshell County, MT, Park County, MT, Petroleum County, MT, Stillwater County, MT, Sweet Grass County, MT, Treasure County, MT, Wheatland County, MT, Yellowstone County, MT

The radar

The Billings radar (KBLX), 101 km from the middle of the area, began a volume at 20:11 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 8.2 hours before the alert went out and 143 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: 194 J/kg
Mixed-layer CIN: -319 J/kg
Mixed-layer LCL: 1098 m above ground
0-6 km bulk shear: 78 kt
0-1 km storm-relative helicity: 56 m²/s²
0-3 km storm-relative helicity: 161 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

815 
ACUS11 KWNS 282013
SWOMCD
SPC MCD 282012 
MTZ000-WYZ000-IDZ000-282215-

MESOSCALE DISCUSSION 0749
NWS STORM PREDICTION CENTER NORMAN OK
0312 PM CDT WED MAY 28 2014

AREAS AFFECTED...MUCH OF MT

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 282012Z - 282215Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...SEVERE STORMS ARE EXPECTED TO FORM LATER THIS
AFTERNOON...WITH LARGE HAIL...DAMAGING WINDS AND A TORNADO OR TWO
EXPECTED. A WATCH IS LIKELY BY 21Z.

DISCUSSION...SURFACE ANALYSIS SHOWS A CONTINUED INFLUX OF LOW-LEVEL
MOISTURE NWWD INTO CNTRL MT WHERE STRONG HEATING ALSO PERSISTS. THE
PRESENCE OF COOL TEMPERATURES ALOFT AS WELL AS AMPLE DEEP LAYER
SHEAR IS RESULTING IN A FAVORABLE ENVIRONMENT FOR SUPERCELLS CAPABLE
OF LARGE HAIL AND/OR BOWING SEGMENTS WITH DAMAGING WINDS. 

THE BEST TORNADO THREAT WOULD APPEAR TO BE ACROSS CNTRL AND NRN MT
WHERE LOW-LEVEL SHEAR IS STRONGER AND WHERE LCL HEIGHTS WILL REMAIN
LOWEST. ANY SUPERCELLS FORMING UPSTREAM AND MOVING INTO THIS
ENVIRONMENT COULD PRODUCE A TORNADO...ASSUMING OUTFLOW DOES NOT GET
OUT OF HAND.

..JEWELL/CORFIDI.. 05/28/2014

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BYZ...GGW...RIW...TFX...PIH...MSO...

LAT...LON   44711303 47191178 49031146 48980944 48290864 47110763
            46660683 45980672 45290734 44850855 44760991 44631210
            44711303

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 27, 6:12 PM MDT	Mesoscale Discussion	SPC	Broadwater, Cascade, Deer Lodge, Fergus, Golden Valley, Granite and 6 more	48 min
May 27, 10:58 PM MDT	Mesoscale Discussion	SPC	Custer, Fallon, Musselshell, Prairie, Rosebud, Treasure	62 min
May 28, 2:51 AM MDT	Mesoscale Discussion	SPC	Dawson, Prairie, Wibaux	114 min
May 28, 2:47 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Broadwater, Carbon, Cascade, Custer, Gallatin and 13 more	6 hr
May 28, 4:59 PM MDT	Severe Thunderstorm Watch	SPC	Blaine, Chouteau, Daniels, Dawson, Fergus, Garfield and 12 more	7 hr

Nearby

Mesoscale Discussions in Montana, 2014 Every mesoscale discussion in 2014

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.