Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 2212

December 25, 2012Ashley County, Chicot County, Arkansas; 19 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at Dec 25, 2012, 12:23 PM CST for Ashley County, Chicot County, Arkansas; 19 parishes in Louisiana. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued
Dec 25, 2012, 12:23 PM CST (18:23 UTC)
Expired
Dec 25, 2012, 1:30 PM CST
In force
67 min
Issued by
the Storm Prediction Center
All 21 counties

Ashley County, AR, Chicot County, AR, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Tensas Parish, LA, Union Parish, LA, West Carroll Parish, LA, Winn Parish, LA

The watches that followed

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

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 6.4 hours before the alert went out and 205 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-pSkew-T log-p diagram, Jackson, MS at 12:00Z on 2012-12-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Jackson, MS at 12:00Z on 2012-12-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 253 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
1 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
659 m above ground
0-6 km bulk shear
42 kt
0-1 km storm-relative helicity
253 m²/s²
0-3 km storm-relative helicity
361 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.4

Open this sounding in Storm Lab

The text

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

799 
ACUS11 KWNS 251824
SWOMCD
SPC MCD 251823
MSZ000-LAZ000-ARZ000-251930-

MESOSCALE DISCUSSION 2212
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CST TUE DEC 25 2012

AREAS AFFECTED...NERN TX INTO NRN MS

CONCERNING...SEVERE THUNDERSTORM WATCH 693...

VALID 251823Z - 251930Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 693
CONTINUES.

SUMMARY...SEVERE CONVECTIVE WIND GUSTS AND LARGE HAIL WILL CONTINUE
AS THE PRIMARY THREATS ACROSS THE WW AREA AS A QLCS PROGRESSES EWD.
AREAS IN THE WAKE OF THE QLCS MAY BE CLEARED FROM THE WW.
MEANWHILE...SUFFICIENT SURFACE-BASED DESTABILIZATION HAS OCCURRED
ACROSS THE SRN PORTION OF THE WW SUCH THAT A TORNADO THREAT EXISTS
/REF MD 2210/. A TORNADO WW WILL BE NEEDED DOWNSTREAM ACROSS
PORTIONS OF MS.

DISCUSSION...A QLCS HAS FORMED RAPIDLY IN RESPONSE TO STRONG FORCING
FOR ASCENT...WITH THE LEADING EDGE CLEARLY DEMARCATED ON 18Z WV
IMAGERY ACROSS E TX. AS THE WARM SECTOR CONTINUES TO EXPAND AND
CONVECTION BECOMES NEAR SURFACE-BASED...A COINCIDENT STRENGTHENING
OF DEEP LAYER WINDS WILL AID IN INCREASING DAMAGING WIND GUSTS
ACROSS THE WW AREA. RECENT SURFACE OBSERVATIONS ACROSS NRN LA
REFLECT GUSTS TO NEAR 50 MPH WITH THE PRIMARY LINE OF CONVECTION.
MEANWHILE...TORNADIC POTENTIAL IS INCREASING ACROSS SRN PORTIONS OF
THE WW /REF MCD 2210/...WITH A STRONG COUPLET RECENTLY NOTED OVER
VERNON PARISH JUST S OF SVR WW 693.

..DISPIGNA.. 12/25/2012

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

ATTN...WFO...JAN...LIX...LZK...LCH...SHV...

LAT...LON   31439254 31379312 32029312 32769295 33069309 33469121
            32479101 31929118 31169162 31499220 31439254

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 25, 9:02 AM CSTSevere Thunderstorm WatchSPCAshley, Chicot, Union7 hr
Dec 25, 12:11 PM CSTMesoscale DiscussionSPCCleburne, Conway, Crawford, Faulkner, Franklin, Garland and 20 more5 hr
Dec 25, 1:00 PM CSTMesoscale DiscussionSPCColumbia, Hempstead, Lafayette, Little River, Miller, Nevada5 hr
Dec 25, 2:14 PM CSTMesoscale DiscussionSPCBaxter, Boone, Carroll, Clay, Craighead, Cross and 10 more4 hr
Dec 25, 3:22 PM CSTMesoscale DiscussionSPCChicot53 min
Dec 25, 1:01 AM CSTMesoscale DiscussionSPCAllen, Beauregard, Sabine, Vernon59 min
Dec 25, 1:37 AM CSTSevere Thunderstorm WatchSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, De Soto and 9 more7 hr
Dec 25, 5:56 AM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, De Soto and 10 more94 min
Dec 25, 7:00 AM CSTMesoscale DiscussionSPCAcadia, Allen, Ascension, Assumption, Beauregard, Calcasieu and 24 more60 min
Dec 25, 7:28 AM CSTTornado WatchSPCAcadia, Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia and 19 more6 hr
Dec 25, 8:46 AM CSTMesoscale DiscussionSPCAllen, Avoyelles, Beauregard, Bienville, Calcasieu, Caldwell and 21 more59 min
Dec 25, 9:17 AM CSTTornado WatchSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 10 more8 hr
Dec 25, 12:19 PM CSTMesoscale DiscussionSPCAcadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 35 more71 min
Dec 25, 12:58 PM CSTTornado Watch PDSSPCAscension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 20 more9 hr
Dec 25, 3:44 PM CSTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 19 more91 min

Nearby

Mesoscale Discussions in Louisiana, 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.