[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 201823
SWOMCD
SPC MCD 201823 
TXZ000-202100-

MESOSCALE DISCUSSION 2412
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CST SAT NOV 20 2004

AREAS AFFECTED...SRN AND S CNTRL TX

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 201823Z - 202100Z

POTENTIAL FOR SURFACE BASED STORMS EXPECTED TO INCREASE THROUGH THE
AFTERNOON OVER PARTS OF S TX. PRIMARY THREATS WILL BE FOR AN
ISOLATED TORNADO OR TWO...ISOLATED STRONG WIND GUSTS AND MARGINALLY
SEVERE HAIL. OVERALL THREAT DOES NOT APPEAR TO WARRANT A WW AT THIS
TIME...BUT AREA WILL CONTINUE TO BE MONITORED FOR A POSSIBLE WW FOR
LATER THIS AFTERNOON.

AT MID-DAY A QUASISTATIONARY FRONT EXTENDS FROM OFF THE SE TX COAST
WSWWD TO JUST S OF VICTORIA TO NEAR LAREDO. A LONG FETCH OF
SUBTROPICAL MOISTURE HAS CONTRIBUTED TO EXTENSIVE MIDDLE AND HIGH
LEVEL CLOUDS ACROSS MUCH OF S TX AND CONTINUES TO MITIGATE SURFACE
HEATING. THINNING/BREAKS IN CLOUDS ALONG COASTAL S TX HAVE ALLOWED
TEMPERATURES TO WARM INTO THE UPPER 70S JUST S OF THE FRONT WITH
MLCAPE FROM 1000 TO 1500 J/KG.
 
RUC DATA SHOW NOSE OF WARMER MID LEVEL AIR ADVECTING NEWD THROUGH 
COASTAL S TX WITH TIME...RESULTING IN AN INVERSION AROUND 2.6 KM.
THIS WILL LIMIT LAPSE RATES AND CAPE IN THE 1-3 KM LAYER...SLOW THE
DEVELOPMENT OF DEEPER MORE ROBUST CONVECTION...AND HAS POTENTIAL TO
MITIGATE OVERALL SEVERE POTENTIAL. HOWEVER...AS THE BOUNDARY LAYER
CONTINUES TO WARM...A SLOW INCREASE IN CONVECTIVE INTENSITY IS
EXPECTED IN VICINITY OF THE BOUNDARY THROUGH THE AFTERNOON WHERE
DEEP LAYER AND LOW LEVEL SHEAR IS SUPPORTIVE OF SUPERCELLS. 

OTHERWISE...ELEVATED CONVECTION WILL CONTINUE N OF THE BOUNDARY INTO
S CNTRL AND CNTRL TX. EFFECTIVE SHEAR IS SUPPORTIVE OF ELEVATED
SUPERCELLS WITH THREAT FOR MAINLY HAIL. HOWEVER... OVERALL HAIL
POTENTIAL WILL BE LIMITED BY MODEST MID LEVEL LAPSE RATES AND CAPE.

..DIAL.. 11/20/2004

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

ATTN...WFO...HGX...CRP...EWX...

28349671 28789560 29259599 28999771 28159829 27789762 

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