ZCZC SPCSWOMCD ALL
ACUS11 KWNS 182306 
SPC MCD 182306 
LAZ000-TXZ000-190030-

MESOSCALE DISCUSSION 0170
NWS STORM PREDICTION CENTER NORMAN OK
0506 PM CST MON FEB 18 2013

AREAS AFFECTED...ERN TX...WRN LA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 182306Z - 190030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG A
DRYLINE/PRE-FRONTAL CONFLUENCE ZONE AND SEWD PROGRESSING COLD FRONT
DURING THE EVENING OVER ERN TX. IF STORMS DEVELOP...THEY ARE
EXPECTED TO MOVE EWD INTO WRN LA BY 03Z...BEHIND PRE-FRONTAL WARM
CONVEYOR BELT CONVECTION. MARGINALLY SEVERE HAIL WOULD BE THE
PRIMARY THREAT...ALONG WITH ISOLATED DAMAGING WIND GUSTS IF ACTIVITY
CAN ORGANIZE INTO A LINE.

DISCUSSION...MESOANALYSIS AT 22-23Z SHOWS A SURFACE COLD FRONT WAS
PROGRESSING ESEWD INTO CNTRL AR AND NERN TX. A DRYLINE/PRE-FRONTAL
CONFLUENCE ZONE EXTENDED SWWD FROM THE NERN TX FRONTAL
SEGMENT...WHILE WARM CONVEYOR BELT SHOWERS AND ISOLATED
THUNDERSTORMS WERE OCCURRING ALONG AN AXIS FROM HOU INTO NRN LA.
VISIBLE SATELLITE IMAGERY SHOWS TOWERING CUMULUS OCCURRING ALONG THE
DRYLINE...WHERE STEEP LOW-LEVEL LAPSE RATES ARE AIDING IN STRONG
BOUNDARY LAYER DESTABILIZATION. UPPER 50S TO LOW 60S DEWPOINTS WERE
PRESENT AHEAD OF THE CUMULUS LINE...WHICH IS AIDING IN SBCAPE VALUES
FROM 500-1500 J/KG. 

AS THE EVENING PROGRESSES...THE COLD FRONT WILL CONTINUE TO OVERTAKE
THE DRYLINE...LEADING TO INCREASING MESOSCALE FORCING FOR ASCENT AND
AN INCREASED PROBABILITY FOR THUNDERSTORM DEVELOPMENT/COVERAGE.
HOWEVER...SHORT-TERM MODEL GUIDANCE INDICATES MIDLEVEL HEIGHTS AND
TEMPERATURES WILL BEGIN TO RISE DURING THE NIGHT...WHICH WILL BE A
NEGATIVE FACTOR FOR ROBUST DEEP MOIST CONVECTION. THUS...THE SEVERE
WEATHER THREAT IS CURRENTLY EXPECTED TO BE MARGINAL...MAINLY IN THE
FORM OF ISOLATED SPORADIC HAIL NEAR 1 INCH IN DIAMETER. IF STORMS
HAPPEN TO ORGANIZE INTO A LINE...THEN THE POTENTIAL FOR ISOLATED
DAMAGING WIND GUSTS WOULD INCREASE. CONVECTIVE TRENDS WILL CONTINUE
TO BE MONITORED.

..GARNER/EDWARDS.. 02/18/2013

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

ATTN...WFO...LCH...SHV...HGX...FWD...EWX...

LAT...LON   30689730 32109551 31829334 30679320 30079691 30689730 

NNNN