Alert archive / Montana / Mesoscale Discussions in 2012

Mesoscale Discussion 1099

June 8, 20129 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jun 8, 2012, 2:52 PM MDT for 9 counties in Montana. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued: Jun 8, 2012, 2:52 PM MDT (20:52 UTC)
Expired: Jun 8, 2012, 3:45 PM MDT
In force: 53 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Blaine County, MT, Daniels County, MT, Fergus County, MT, Garfield County, MT, McCone County, MT, Musselshell County, MT, Petroleum County, MT, Phillips County, MT, Valley County, MT

The radar

The Glasgow radar (KGGW), 82 km from the middle of the area, began a volume at 20:53 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.

Severe Thunderstorm Watch 363Jun 8, 5:45 PM MDT

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 8.9 hours before the alert went out and 84 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: 1188 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 42 m²/s²
0-3 km storm-relative helicity: 98 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

651 
ACUS11 KWNS 082053
SWOMCD
SPC MCD 082052
MTZ000-082145-

MESOSCALE DISCUSSION 1099
NWS STORM PREDICTION CENTER NORMAN OK
0352 PM CDT FRI JUN 08 2012

AREAS AFFECTED...NERN MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 082052Z - 082145Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...A GRADUAL INCREASE IN TSTM COVERAGE IS EXPECTED THROUGH
LATE AFTERNOON ACROSS NERN MT. THE ENVIRONMENT WILL BECOME
INCREASINGLY FAVORABLE FOR LARGE HAIL AND ISOLATED DMGG WIND
GUSTS...AND CONVECTIVE TRENDS WILL BE MONITORED FOR POTENTIAL WW
ISSUANCE LATER THIS AFTERNOON AND EVENING.

DISCUSSION...RECENT VISIBLE SATELLITE LOOP SHOWS INCREASING TOWERING
CU FIELD /PRIMARILY ANCHORED TO THE HIGHER TERRAIN/ OVER PORTIONS OF
CNTRL MT. ONE EXCEPTION IS A PERSISTENT/REGENERATING STORM OVER
BLAINE COUNTY...WHICH HAS SHOWN RADAR INDICATIONS FOR POTENTIALLY
SUB-SEVERE HAIL. STRONG SFC HEATING /TEMPS IN THE UPPER 70S AT 20Z/
...UPSLOPE E-SELY LOW-LEVEL FLOW...AND INCREASING LARGE-SCALE
ASCENT/HEIGHT FALLS ASSOCIATED WITH A POWERFUL NWRN CONUS UPPER
TROUGH...SHOULD SUPPORT AN INCREASE IN TSTM COVERAGE DURING THE NEXT
2-3 HRS. THE EXACT EVOLUTION OF CONVECTION IS SOMEWHAT
UNCERTAIN...BUT RECENT CONVECTION-ALLOWING GUIDANCE /INCLUDING THE
18Z WRF-HRRR/ INDICATES DISCRETE STORMS OR SMALL CLUSTERS SHOULD
EVENTUALLY MOVE OFF THE HIGHER TERRAIN EWD TOWARDS THE HIGH PLAINS
OF ERN MT.

ALTHOUGH INSTABILITY APPEARS RATHER MARGINAL /MLCAPE VALUES AOB 500
J/KG PER MODIFIED 20Z GGW SOUNDING/...FURTHER HEATING AND MOISTURE
ADVECTION FROM THE SE WILL CONTINUE TO DESTABILIZE THE ENVIRONMENT
THROUGH THIS EVENING...BECOMING MORE FAVORABLE FOR SUSTAINING STRONG
UPDRAFTS. ADDITIONALLY...ESELY LOW-LEVEL FLOW BENEATH MODERATE
MIDLEVEL SWLYS WILL YIELD EFFECTIVE SHEAR VALUES OF 50-60 KTS. THIS
ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELLS CAPABLE OF PRODUCING
LARGE HAIL AND DMGG WIND GUSTS...AND MAY NECESSITATE ISSUANCE OF A
WW BY THE EARLY EVENING.

..ROGERS/MEAD.. 06/08/2012

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

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

LAT...LON   48990556 48080527 47200534 46560592 46270739 46340860
            46760963 47760980 48970926 48990556

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 8, 5:07 PM MDT	Mesoscale Discussion	SPC	Custer, Daniels, Dawson, Garfield, McCone, Petroleum and 6 more	53 min
Jun 8, 5:41 PM MDT	Severe Thunderstorm Watch	SPC	Custer, Daniels, Dawson, Fallon, Garfield, McCone and 10 more	9 hr

Nearby

Mesoscale Discussions in Montana, 2012 Every mesoscale discussion in 2012

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.