Alert archive / Montana / Mesoscale Discussions in 2012
Mesoscale Discussion 1346
The Storm Prediction Center issued this mesoscale discussion at Jul 1, 2012, 4:34 PM MDT for 25 counties in Montana. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Jul 1, 2012, 4:34 PM MDT (22:34 UTC)
- Expired
- Jul 1, 2012, 6:00 PM MDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 80%
All 25 counties
Beaverhead County, MT, Blaine County, MT, Broadwater County, MT, Carbon County, MT, Cascade County, MT, Chouteau County, MT, Deer Lodge County, MT, Fergus County, MT, Gallatin County, MT, Golden Valley County, MT, Hill County, MT, Jefferson County, MT, Judith Basin County, MT, Lewis and Clark County, MT, Liberty County, MT, Madison County, MT, Meagher County, MT, Musselshell County, MT, Park County, MT, Powell County, MT, Silver Bow County, MT, Stillwater County, MT, Sweet Grass County, MT, Wheatland County, MT, Yellowstone County, MT
The radar
The Great Falls radar (KTFX), 121 km from the middle of the area, began a volume at 22:37 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, 10.6 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.
- Mixed-layer CAPE
- 14 J/kg
- Mixed-layer CIN
- -587 J/kg
- Mixed-layer LCL
- 1687 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 117 m²/s²
- 0-3 km storm-relative helicity
- 36 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
541
ACUS11 KWNS 012235
SWOMCD
SPC MCD 012234
MTZ000-020000-
MESOSCALE DISCUSSION 1346
NWS STORM PREDICTION CENTER NORMAN OK
0534 PM CDT SUN JUL 01 2012
AREAS AFFECTED...PORTIONS WRN/CENTRAL MT.
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 012234Z - 020000Z
PROBABILITY OF WATCH ISSUANCE...80 PERCENT
SUMMARY...CONVECTIVE COVERAGE IS INCREASING OVER MTNS OF SWRN MT AND
ADJACENT PORTIONS E-CENTRAL ID...INITIALLY WELL W OF WW 449...IN
ENVIRONMENT CHARACTERIZED BY FAVORABLE MOISTURE AND DEEP-LAYER
SHEAR. DAMAGING GUSTS AND LARGE HAIL EACH ARE ANTICIPATED WITH MOST
INTENSE/PERSISTENT CELLS AS REGIME SPREADS/EXPANDS NEWD ACROSS
PORTIONS WRN/CENTRAL MT THRU REMAINDER AFTERNOON INTO EVENING.
DISCUSSION...MOISTURE CHANNEL IMAGERY INDICATES SHORTWAVE TROUGH
ALOFT...MOVING NEWD ACROSS CENTRAL ID TOWARD WRN MT. IN ADVANCE OF
THIS FEATURE...VWP...MODIFIED RAOBS AND MODEL SOUNDINGS SHOW
FAVORABLE DEEP-LAYER SHEAR OVER THIS REGION...JUXTAPOSING WITH
INCREASING LARGE-SCALE ASCENT/DESTABILIZATION ALOFT. BROAD AREA OF
50-60 KT EFFECTIVE SHEAR MAGNITUDE IS EVIDENT OVER WRN TO CENTRAL
MT...IN SUPPORT OF ORGANIZED SVR POTENTIAL INCLUDING A FEW
SUPERCELLS. SFC MESOANALYSIS SHOWED CYCLONES OVER ERN AB AND ALSO
NERN MT NEAR GGW...CONNECTED BY OCCLUDED FRONT. COLD FRONT IS DRAWN
FROM MT LOW ARCHING SWD/SWWD TO ANOTHER LOW NEAR GEY. BEHIND THIS
FRONT...MOISTURE REMAINS AT LEAST MRGLLY FAVORABLE WITH WWD EXTENT
AND ELEVATION...INCLUDING ANOMALOUSLY HIGH 50S/60S DEW POINTS IN
COOLER AIR OVER NRN ID/NWRN MT...W OF GREATEST SVR POTENTIAL.
DIABATIC SFC HEATING AND VERTICAL MIXING HAS RENDERED LOWER DEW
POINT VALUES OVER WRN/CENTRAL MT AND E-CENTRAL ID...BUT MAINTAINED
500-1500 MLCAPE AND MINIMAL MLCINH IN SUPPORT OF TSTM
FORMATION/MAINTENANCE. IN THIS ENVIRONMENT...PRIND TSTMS ALREADY
MOVING NEWD ACROSS SWRN MT WILL BE MAINTAINED AND POSE SVR RISK...AS
WILL ANY ADDITIONAL/SUSTAINED DEVELOPMENT OVER DISCUSSION AREA.
..EDWARDS/HART.. 07/01/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BYZ...GGW...RIW...TFX...MSO...
LAT...LON 49000823 47840883 46800865 46660778 46020770 45060840
44951209 44811301 45851375 47261273 49041122 49000823SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 30, 8:33 PM MDT | Mesoscale Discussion | SPC | Flathead, Lake, Lincoln, Mineral, Missoula, Sanders | 2 hr |
| Jul 1, 2:40 PM MDT | Mesoscale Discussion | SPC | Carter, Custer, Daniels, Dawson, Fallon, Garfield and 10 more | 2 hr |
| Jul 1, 4:04 PM MDT | Severe Thunderstorm Watch | SPC | Big Horn, Carter, Custer, Daniels, Dawson, Fallon and 13 more | 9 hr |
| Jul 1, 5:04 PM MDT | Severe Thunderstorm Watch | SPC | Beaverhead, Blaine, Broadwater, Carbon, Cascade, Chouteau and 18 more | 6 hr |
Nearby
Mesoscale Discussions in Montana, 2012Every 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.