Alert archive / Louisiana / Mesoscale Discussions in 2012
Mesoscale Discussion 2123
The Storm Prediction Center issued this mesoscale discussion at Nov 26, 2012, 3:34 PM CST for Columbia County, Lafayette County, Union County, Arkansas; 24 parishes in Louisiana; 22 counties in Texas. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Nov 26, 2012, 3:34 PM CST (21:34 UTC)
- Expired
- Nov 26, 2012, 5:00 PM CST
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 49 counties
Columbia County, AR, Lafayette County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Anderson County, TX, Angelina County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Gregg County, TX, Harrison County, TX, Henderson County, TX, Houston County, TX, Marion County, TX, Morris County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Smith County, TX, Trinity County, TX, Upshur County, TX, Van Zandt County, TX, Wood County, TX
The radar
The Shreveport radar (KSHV), 56 km from the middle of the area, began a volume at 21:36 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
Shreveport, LA (KSHV), launched 12:00Z, 9.6 hours before the alert went out and 60 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
- 15 J/kg
- Mixed-layer CIN
- -92 J/kg
- Mixed-layer LCL
- 473 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 218 m²/s²
- 0-3 km storm-relative helicity
- 158 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted, in the capitals the NWS used until 2016.
466
ACUS11 KWNS 262134
SWOMCD
SPC MCD 262134
LAZ000-ARZ000-TXZ000-262300-
MESOSCALE DISCUSSION 2123
NWS STORM PREDICTION CENTER NORMAN OK
0334 PM CST MON NOV 26 2012
AREAS AFFECTED...NERN TX...NRN LA...EXTREME SRN AR
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 262134Z - 262300Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...THUNDERSTORMS ARE FORECAST TO DEVELOP ACROSS NERN TX...NRN
LA AND EXTREME SRN AR LATE THIS AFTERNOON AND EVENING. ACTIVITY WILL
EVENTUALLY EVOLVE INTO A LINE AS A COLD FRONT ADVANCES EWD ACROSS
THE AREA. STORMS WILL PRIMARILY POSE A DAMAGING WIND AND LARGE HAIL
THREAT. A WW MAY NEED TO BE ISSUED DURING THE NEXT COUPLE OF HOURS.
DISCUSSION...MESOANALYSIS AT 21Z PLACES A SURFACE LOW IN FAR NERN
TX...WITH A WARM FRONT SLOWLY RETREATING EWD INTO CNTRL PORTIONS OF
LA...AND A COLD FRONT ADVANCING E-SEWD ACROSS CNTRL TX. AMPLE
SUNSHINE HAS AIDED IN WARM SECTOR TEMPERATURES WARMING INTO THE 70S
TO LOW 80S...WHILE AN AXIS OF LOW TO MID 60S DEWPOINTS EXTENDS
N-NEWD FROM THE TX GULF COAST INTO WRN LA. THE WARM/MOIST BOUNDARY
LAYER COMBINED WITH 700-500 MB LAPSE RATES NEAR 7 C/KM IS YIELDING
MLCAPE VALUES ESTIMATED TO BE AROUND 1000-2000 J/KG AHEAD OF THE
COLD FRONT.
VISIBLE SATELLITE IMAGERY AS OF 2115Z SHOWS THE WARM SECTOR IS
CAPPED...WHICH IS ALSO SUPPORTED BY 18Z SHV RAOB.
HOWEVER...LARGE-SCALE ASCENT ASSOCIATED WITH A SERIES OF SRN STREAM
DISTURBANCES EMANATING OUT OF NRN MEXICO...COMBINED WITH FRONTAL
CONVERGENCE/ASCENT ARE FORECAST TO ERODE THE CAPPING INVERSION
DURING THE 22-00Z TIME PERIOD. THIS WILL FAVOR THUNDERSTORM
DEVELOPMENT ALONG THE COLD FRONT AND PERHAPS EWD INVOF THE SURFACE
LOW AND WARM FRONT. DEEP-LAYER SHEAR ON THE ORDER OF 30-40 KT WILL
SUPPORT MULTICELL CLUSTERS AND PERHAPS A FEW SUPERCELLS POSING A
THREAT FOR LARGE HAIL AND DAMAGING WIND GUSTS. LOW-LEVEL SHEAR
PROFILES WILL NOT BE PARTICULARLY STRONG...THUS ANY TORNADO THREAT
IS EXPECTED TO BE BRIEF AND FOCUSED NEAR THE LOW WHERE BACKED
SURFACE WINDS WILL BE MOST PROBABLE.
BY NIGHT...STORMS ARE FORECAST TO ORGANIZE INTO A LINE AS THE COLD
FRONT ADVANCES EWD...WITH THE THREAT FOR HAIL AND STRONG/SVR WIND
GUSTS CONTINUING.
..GARNER/EDWARDS.. 11/26/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...JAN...LCH...SHV...HGX...FWD...
LAT...LON 30849533 31499614 32559605 33229461 33279249 32889138
31999124 31479198 30929358 30849533SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Nov 26, 5:08 PM CST | Mesoscale Discussion | SPC | Austin, Bastrop, Brazos, Burleson, Caldwell, Chambers and 23 more | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Arkansas, 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.