Post by SKYSUMMIT on Mar 3, 2016 13:42:00 GMT -6
MESOSCALE DISCUSSION 0173
NWS STORM PREDICTION CENTER NORMAN OK
0113 PM CST THU MAR 03 2016
AREAS AFFECTED...PORTIONS OF SRN MS...SRN LA...SWRN AL...WRN FL
PANHANDLE
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 031913Z - 032145Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THERE WILL BE A GRADUALLY INCREASING POTENTIAL FOR
SEVERE-THUNDERSTORM DEVELOPMENT DURING THE NEXT FEW HOURS ACROSS
PARTS OF THE LOWER MS VALLEY / DEEP SOUTH AND VICINITY. SVR
HAIL/WIND AND PERHAPS A COUPLE OF TORNADOES MAY OCCUR. THERE IS SOME
UNCERTAINTY REGARDING THE MAGNITUDE OF THE SVR RISK. WHILE NOT
IMMEDIATELY LIKELY...THE ISSUANCE OF A WW WILL BE POSSIBLE.
DISCUSSION...RADAR AND SATELLITE LOOPS IMPLY CONVECTION BECOMING
INCREASINGLY AGITATED ACROSS SRN MS -- WITHIN A BAND OF MID-LEVEL
ASCENT THAT TRAILS TO THE WSW OF AN IMPULSE TRACKING ACROSS PARTS OF
THE TN VALLEY AND SRN APPALACHIANS. SFC OBSERVATIONS HIGHLIGHT AN
OUTFLOW BOUNDARY EXTENDING FROM N OF THE JACKSON MS METRO AREA
ARCING THROUGH THE MERIDIAN MS AREA TO N OF MONTGOMERY AL. TO THE S
OF THIS BOUNDARY...THETA-E IS INCREASING WITHIN THE BOUNDARY
LAYER...AS THE FLOW S/SE OF SFC LOW PRESSURE ANALYZED OVER THE
ARKLAMISS DELTA REGION FACILITATES NEWD/ENEWD FLUXES OF RICHER GULF
MOISTURE INTO THE REGION.
AHEAD OF A COLD FRONT ANALYZED FROM CNTRL AR TO CNTRL TX...POCKETS
OF DIABATIC SFC HEATING OWING TO INSOLATION HAVE BEEN MOST ROBUST
ACROSS PARTS OF CNTRL/SRN LA...WHICH WILL SUPPORT AN INFLUX OF
INSTABILITY ACROSS THE MCD AREA FROM THE W. MEANWHILE...SFC
DEWPOINTS ARE CLIMBING INTO THE MIDDLE 60S ACROSS PARTS OF S-CNTRL
LA...AND SIMILAR/BETTER-MODIFIED GULF MOISTURE WILL SPREAD ACROSS
THE MCD AREA BENEATH A RESIDUAL EML SAMPLED BY EARLIER 12Z LCH AND
LIX RAOBS. THIS WILL SUPPORT MLCAPE INCREASING TO 500-1250 J/KG WITH
DECREASING MLCINH...ENCOURAGING INCREASINGLY INTENSE UPDRAFTS ACROSS
THE MCD AREA IN THE NEXT FEW HOURS. THIS MAY DEVELOP FROM ONGOING
ACTIVITY WITH ADDITIONAL CONVECTIVE DEVELOPMENT POSSIBLE...
ESPECIALLY AS A SECONDARY MID-LEVEL VORT MAX AND RELATED DCVA OVER
THE ARKLAMISS REGION EVENTUALLY GLANCE THE AREA.
VWP DATA AT JACKSON MS AND SLIDELL LA SAMPLED ABUNDANT DEEP SHEAR
SUPPORTING ROTATING TSTMS CAPABLE OF POTENTIALLY SVR HAIL/WIND.
SUFFICIENT LOW-LEVEL HODOGRAPH CURVATURE IN PROXIMITY TO A BOUNDARY
FROM JACKSON MS TO SERN LA/SERN MS SUGGESTS A COUPLE OF TORNADOES
COULD OCCUR -- PARTICULARLY WITH MORE DISCRETE UPDRAFTS THAT INGEST
HIGHER-DEWPOINT/MORE-BUOYANT INFLOW.
PRESENTLY...THERE IS UNCERTAINTY REGARDING THE OVERALL MAGNITUDE OF
THE SVR-TSTM POTENTIAL...OWING TO THE LACK OF SPATIAL OVERLAP
BETWEEN STRONGER DEEP ASCENT AND RICHER MOISTURE/HIGHER INSTABILITY.
FURTHERMORE...THE TENDENCY FOR SFC WINDS TO BE RELATIVELY MORE
VEERED IN THE HIGHER-INSTABILITY AIR...AND THIS INFLUENCE ON
VERTICAL-SHEAR PROFILES...CAST DOUBT ON THE EFFICIENCY FOR
DEEP/ROTATING TSTMS TO MATERIALIZE. THE SVR RISK MAY ONLY GRADUALLY
INCREASE...AND ITS PEAK INTENSITY IS UNCERTAIN. AS SUCH...THE
EVOLVING METEOROLOGICAL SCENARIO WILL BE RE-EVALUATED THROUGHOUT THE
AFTERNOON FOR THE INCREASING SEVERE-THUNDERSTORM POTENTIAL AND
POSSIBLE WATCH ISSUANCE.
..COHEN/HART.. 03/03/2016
