Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 152239
SWOMCD
SPC MCD 152238
ALZ000-MSZ000-LAZ000-160045-

MESOSCALE DISCUSSION 1979
NWS STORM PREDICTION CENTER NORMAN OK
0438 PM CST MON DEC 15 2014

AREAS AFFECTED...PORTIONS OF MISSISSIPPI...WESTERN
ALABAMA...SOUTHEAST LOUISIANA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 152238Z - 160045Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...THE RISK FOR A WEAK TORNADO/STRONG WIND GUST WILL NOT BE
ENTIRELY NEGLIGIBLE INTO THE EARLY EVENING...THOUGH WW ISSUANCE WILL
NOT BE NEEDED.

DISCUSSION...VIS SATELLITE IMAGERY AND SFC OBSERVATIONS INDICATE
ISOLATED TO WIDELY SCATTERED LOW-TOPPED CONVECTION PRODUCING LITTLE
TO NO LIGHTNING EVOLVING IN TWO REGIMES:

/1/ ALONG A REMNANT TROUGH/WIND-SHIFT AXIS ANALYZED ALONG THE MS
RIVER FROM THE GREENVILLE AREA SWWD INTO CNTRL LA -- WHICH IS
SHIFTING EWD...
/2/ ALONG A CONFLUENCE AXIS ANALYZED TO THE E OF THE TROUGH --
EXTENDING FROM S-CNTRL LA INTO CNTRL MS E OF JACKSON TO NEAR
STARKVILLE.

MOISTURE-CHANNEL IMAGERY INDICATES A PROMINENT DRY SLOT SPREADING
ACROSS THE AREA...WITH LARGE-SCALE DCVA BEING RELEGATED TO HIGHER
LATITUDES /E.G. MID MS VALLEY/. THIS IS LARGELY LIMITING THE
CONVECTIVE COVERAGE. HOWEVER...WITH 30-40 KT OF 1-2-KM FLOW SAMPLED
BY THE JACKSON VWP...SUFFICIENT LOW-LEVEL SHEAR EXISTS FOR A FEW
ROTATING CONVECTIVE ELEMENTS -- E.G. ONE CURRENTLY ALONG THE
SIMPSON/JEFFERSON DAVIS COUNTY LINE. MODIFICATIONS TO THE 12Z
JACKSON RAOB TO ACCOUNT FOR MODEST BOUNDARY-LAYER MOISTENING AND
DIURNAL DIABATIC HEATING SUGGEST AROUND 500 J/KG OF SBCAPE E OF THE
WIND-SHIFT AXIS. THIS COULD SUPPORT A FEW MORE INSTANCES OF MODESTLY
ROTATING UPDRAFTS...WITH THE RISK FOR A WEAK TORNADO/STRONG WIND
GUST NOT ENTIRELY NEGLIGIBLE. HOWEVER...PROMINENT CAPPING LAYERS
BETWEEN H7 AND H6 WILL LARGELY STUNT VERTICAL VORTICITY
STRETCHING/STORM-INDUCED MID-LEVEL HYDRODYNAMIC PRESSURE
PERTURBATIONS THAT WOULD OTHERWISE YIELD A MORE SUBSTANTIAL SVR-TSTM
RISK. ANY SVR RISK WILL QUICKLY CEASE FOLLOWING DUSK.

..COHEN/EDWARDS.. 12/15/2014

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

ATTN...WFO...BMX...MOB...MEG...JAN...LIX...

LAT...LON   33699001 33908893 33598823 32448820 31198908 30659003
            30629113 31029161 31609150 32709087 33699001



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