Alert archive / Montana / Mesoscale Discussions in 2012

Mesoscale Discussion 1276

June 25, 201210 counties in Montana

The Storm Prediction Center issued this mesoscale discussion at Jun 25, 2012, 3:35 PM MDT for 10 counties in Montana. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Jun 25, 2012, 3:35 PM MDT (21:35 UTC)
Expired: Jun 25, 2012, 5:00 PM MDT
In force: 85 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Blaine County, MT, Chouteau County, MT, Garfield County, MT, Glacier County, MT, Hill County, MT, Liberty County, MT, Phillips County, MT, Pondera County, MT, Toole County, MT, Valley County, MT

The radar

The Great Falls radar (KTFX), 114 km from the middle of the area, began a volume at 21:35 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 430Jun 25, 4:00 PM MDT

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 9.6 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: 1300 J/kg
Mixed-layer CIN: -223 J/kg
Mixed-layer LCL: 551 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 17 m²/s²
0-3 km storm-relative helicity: 263 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.

572 
ACUS11 KWNS 252136
SWOMCD
SPC MCD 252135
MTZ000-252300-

MESOSCALE DISCUSSION 1276
NWS STORM PREDICTION CENTER NORMAN OK
0435 PM CDT MON JUN 25 2012

AREAS AFFECTED...NWRN THROUGH CNTRL MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 252135Z - 252300Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...POTENTIAL EXISTS FOR STORMS TO INCREASE IN INTENSITY AS
THEY MOVE NWD OFF THE HIGHER TERRAIN INTO THE HIGH PLAINS OF MT.
SUPERCELLS AND BOWING SEGMENTS WITH ISOLATED LARGE HAIL AND DAMAGING
WIND WILL BE THE PRIMARY THREATS.

DISCUSSION...EARLY THIS EVENING ELY LOW LEVEL POST FRONTAL WINDS
HAVE ADVECTED LOW 60S DEWPOINTS WWD THROUGH MUCH OF NRN AND CNTRL MT
BENEATH STEEP MID LEVEL LAPSE RATES CONTRIBUTING TO AN AXIS OF
1500-3000 J/KG MLCAPE. LATEST VISIBLE IMAGERY SHOWS CONVECTION
INCREASING OVER THE HIGHER TERRAIN OF SRN/CNTRL THROUGH WRN MT...AND
HIGH BASED STORMS ARE EXPECTED TO EVENTUALLY DEVELOP. NWRN FRINGE OF
UPPER RIDGE AXIS IS BEING SUPPRESSED BY A NNEWD EJECTING SPEED MAX
WITH MODEST HEIGHT FALLS INDICATED OVER WRN AND CNTRL MT.
TEMPERATURES HAVE RISEN INTO THE UPPER 80S AND LOWER 90S NE OF THE
HIGHER TERRAIN AND THE CAP IS SUFFICIENTLY WEAK FOR STORMS TO
DEVELOP OVER THE MOUNTAINS. ONCE INITIATED...VERTICAL SHEAR OF 40-50
KT WILL SUPPORT SUPERCELL STRUCTURES WHICH WILL LIKELY SURVIVE AND
INTENSIFY AS THEY MOVE INTO THE MOIST BOUNDARY LAYER.

..DIAL/MEAD.. 06/25/2012

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

ATTN...WFO...GGW...TFX...MSO...

LAT...LON   48891371 48800984 48410610 47020598 47330980 48011304
            48891371

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 25, 2:09 PM MDT	Mesoscale Discussion	SPC	Carter, Custer, Dawson, Fallon, Powder River, Prairie and 2 more	2 hr
Jun 25, 3:07 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Rosebud and 1 more	7 hr
Jun 25, 4:01 PM MDT	Severe Thunderstorm Watch	SPC	Blaine, Cascade, Chouteau, Daniels, Dawson, Fergus and 18 more	9 hr
Jun 25, 5:26 PM MDT	Mesoscale Discussion	SPC	Carter, Custer, Fallon, Powder River	94 min

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.