Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 24

January 17, 201220 parishes in Louisiana; 30 counties in Mississippi; Sabine County, San Augustine County, Shelby County, Texas

The Storm Prediction Center issued this mesoscale discussion at Jan 17, 2012, 9:26 AM CST for 20 parishes in Louisiana; 30 counties in Mississippi; Sabine County, San Augustine County, Shelby County, Texas. It was in force for 34 min.

The area

The outline as issued.

The facts

Issued
Jan 17, 2012, 9:26 AM CST (15:26 UTC)
Expired
Jan 17, 2012, 10:00 AM CST
In force
34 min
Issued by
the Storm Prediction Center
All 53 counties

Avoyelles Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, De Soto Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Vernon Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Greene County, MS, Hinds County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Newton County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Walthall County, MS, Warren County, MS, Wayne County, MS, Wilkinson County, MS, Sabine County, TX, San Augustine County, TX, Shelby County, TX

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 3.4 hours before the alert went out and 190 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 2012-01-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 83 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 2012-01-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 419 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
83 J/kg
Mixed-layer CIN
-191 J/kg
Mixed-layer LCL
583 m above ground
0-6 km bulk shear
48 kt
0-1 km storm-relative helicity
419 m²/s²
0-3 km storm-relative helicity
425 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.3

Open this sounding in Storm Lab

The text

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

051 
ACUS11 KWNS 171526
SWOMCD
SPC MCD 171526 
ALZ000-MSZ000-LAZ000-TXZ000-171600-

MESOSCALE DISCUSSION 0024
NWS STORM PREDICTION CENTER NORMAN OK
0926 AM CST TUE JAN 17 2012

AREAS AFFECTED...EXTREME E TX/NRN AND CENTRAL LA/SRN MS

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 171526Z - 171600Z

WW WILL LIKELY NEED TO BE ISSUED FROM EXTREME E TX EWD THROUGH MUCH
OF NRN/CENTRAL LA TO SRN MS.

REGIONAL RADAR IMAGERY SHOWED TSTMS CONTINUING TO DEVELOP WITHIN A
CORRIDOR OF ONGOING LOW LEVEL MOISTURE/WAA ACROSS THE WARM SECTOR. 
ASCENT IN ADVANCE OF A SRN STREAM SHORTWAVE TROUGH...CURRENTLY
MOVING INTO CENTRAL TX PER WATER VAPOR IMAGERY...AND WEAK HEIGHT
FALLS ATTENDANT TO A PROGRESSIVE TROUGH LOCATED N OF THE DISCUSSION
AREA COMBINED WITH LOW LEVEL WAA APPEAR TO BE THE PRIMARY FORCING
MECHANISMS.  DESPITE RELATIVELY WEAK LOW LEVEL LAPSE RATES AT THIS
TIME AND CLOUDINESS LIMITING DIABATIC HEATING...THE PRESENCE OF
STEEP MIDLEVEL LAPSE RATES AND SURFACE DEWPOINTS IN THE 60S ARE
SUPPORTING A MODERATELY UNSTABLE AIR MASS ACROSS LA /MLCAPE AOA 1000
J PER KG/.

12Z RAOBS AND FORECAST SOUNDINGS INDICATE A WARM NOSE/LAYER ACROSS
THE LOWER MS VALLEY THAT MAY CONTINUE TO ACT AS A LIMITING FACTOR
FOR OVERALL COVERAGE OF MORE ROBUST UPDRAFTS/STRONGER ACTIVITY. 
HOWEVER...GIVEN THE PRESENCE OF MODERATE INSTABILITY AND EFFECTIVE
BULK SHEAR OF 40-50 KT ORIENTED PARALLEL TO THE SWD ADVANCING COLD
FRONT...ORGANIZED LINEAR STRUCTURES REMAIN LIKELY WITH AT LEAST A
THREAT FOR ISOLATED HAIL AND DAMAGING WINDS.  FORCING FOR ASCENT
ATTENDANT TO THE TX SHORTWAVE TROUGH COULD WEAKEN THE CAP
SUFFICIENTLY FOR SURFACE BASED STORMS WHICH WOULD INCREASE THE
TORNADO POTENTIAL LATER THIS MORNING INTO THE AFTERNOON...GIVEN
STRONG LOW LEVEL SPEED SHEAR AND SRH EXCEEDING 300 M2/S2.

..PETERS.. 01/17/2012

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

ATTN...WFO...MOB...JAN...LIX...LCH...SHV...

LAT...LON   31069420 31799431 32269358 32519235 32599043 32508856
            31698844 30998848 30949107 30909346 30909381 31069420

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jan 17, 3:45 PM CSTMesoscale DiscussionSPCAllen, Avoyelles, Beauregard, Concordia, East Feliciana, Evangeline and 5 more60 min

Nearby

Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Texas, 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.