ZCZC SPCSWOMCD ALL
ACUS11 KWNS 191730 
SPC MCD 191730 
TNZ000-ALZ000-MSZ000-ARZ000-192000-

MESOSCALE DISCUSSION 1717
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED AUG 19 2015

AREAS AFFECTED...CNTRL/NRN/ERN MS...NRN/WRN AL...MIDDLE/WRN
TN...SERN AR

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 191730Z - 192000Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTMS AFFECTING THE REGION THIS AFTERNOON WILL HAVE THE
POTENTIAL TO POSE A RISK FOR PRODUCING ISOLATED TO PERHAPS WIDELY
SCATTERED DMGG WIND GUSTS. WHILE NOT IMMEDIATELY LIKELY...THE
ISSUANCE OF A SEVERE THUNDERSTORM WATCH MAY BE NEEDED FOR PARTS OF
THE AREA THIS AFTERNOON.

DISCUSSION...WITHIN A NIL-CAPPING...RICH-TROPOSPHERIC-MOISTURE
REGIME SAMPLED BY AREA 12Z RAOBS...CONVECTION WILL CONTINUE TO
DEVELOP AND SPREAD NEWD ACROSS THE REGION THROUGH THE AFTERNOON. THE
NRN EXTENT OF THE LEADING EDGE OF A LOOSELY ORGANIZED MCS OVER THE
CNTRL GULF COAST IS SPREADING NEWD THROUGH THE VICKSBURG MS AND
JACKSON MS AREAS TO THE PINE BELT...AND WILL CONTINUE DEVELOPING
NEWD ACROSS PARTS OF THE ARKLAMISS REGION AND SURROUNDING AREAS.
VISIBLE SATELLITE IMAGERY INDICATES CONVECTION DEEPENING IN ADVANCE
OF THIS ACTIVITY IN TANDEM WITH DIURNALLY INVIGORATED PBL
CIRCULATIONS INTO NRN MS. FRONTAL ASCENT OFFERED BY A BAROCLINIC
ZONE PROGRESSING SEWD ACROSS THE MID-SOUTH MAY ALSO OFFER EVENTUAL
DEVELOPMENT OF SFC-BASED CONVECTION FOLLOWING ONGOING ANA-FRONTAL
ACTIVITY PROVIDED ADDITIONAL PRE-FRONTAL SFC DIABATIC HEATING.

JACKSON MS...MEMPHIS TN...AND NASHVILLE TN VWPS ARE SAMPLING
AROUND-30-KT MID-LEVEL SWLYS WITH MODERATE 1-2-KM-AGL FLOW /20-30
KT/ THAT MAY SUPPORT NEWD-MOVING COLD POOLS OFFERING A RISK FOR
STRONG TO PERHAPS DMGG WIND GUSTS -- ASSISTED BY VERTICAL TRANSPORT
OF RELATED HORIZONTAL MOMENTUM IN CONVECTION. LOCAL MULTICELL
CLUSTERS EMANATING FROM AMALGAMATING COLD POOLS WOULD LOCALLY
ENHANCE SUCH POTENTIAL...AS MLCAPE AROUND 1000-2500 J/KG SUPPORTS
SOME INTENSE UPDRAFTS. PW VALUES AROUND 2.0-2.3 INCHES PER GPS DATA
IMPLY THAT WATER-LOADING WILL FURTHER AUGMENT WET-MICROBURST
POTENTIAL.

REGARDLESS...EARLIER RAOBS INDICATE POOR MID-LEVEL LAPSE
RATES...WHICH MAY BE A SUBSTANTIAL DETERRENT TO THE OVERALL SVR-TSTM
THREAT. FURTHERMORE...WATER-VAPOR LOOPS IMPLY A DEARTH OF UPWARD
MOTION AT THE SYNOPTIC SCALE...REDUCING OVERALL CONFIDENCE IN A
WW-WARRANTING SVR RISK. REGARDLESS...CONVECTIVE TRENDS WILL BE
MONITORED THROUGHOUT THE DAY...AND A WW COULD BE NEEDED IF A MORE
ORGANIZED SVR RISK WERE TO BECOME APPARENT.

..COHEN/CORFIDI.. 08/19/2015

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

ATTN...WFO...MRX...OHX...BMX...HUN...MOB...MEG...JAN...LZK...

LAT...LON   31918839 31438920 31788986 32489032 33519129 34059145
            34589099 35099017 36148844 36448728 36368603 35878563
            34878593 33498688 32458784 31918839 

NNNN