ZCZC SPCSWOMCD ALL ACUS11 KWNS 030823 SPC MCD 030823 TXZ000-031100- MESOSCALE DISCUSSION 1863 NWS STORM PREDICTION CENTER NORMAN OK 0223 AM CST SAT DEC 03 2016 AREAS AFFECTED...PORTIONS OF THE IMMEDIATE UPPER TEXAS COAST CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 030823Z - 031100Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...A CONDITIONAL RISK EXISTS FOR SURFACE-BASED SUPERCELLS TO AFFECT THE IMMEDIATE COASTAL AREAS BETWEEN MATAGORDA AND CHAMBERS COUNTIES...AND A TORNADO CANNOT BE RULED OUT FOR ANY WELL-ORGANIZED STORM-SCALE CIRCULATIONS THAT CAN REACH THE SHORE. DUE TO THE CONDITIONALITY AND LIMITED SPATIAL EXTENT OF THE THREAT AREA...A WATCH APPEARS UNLIKELY AT THIS TIME. DISCUSSION...SURFACE MESOANALYSES SHOWS A SLOW-MOVING WARM FRONT FROM ZAPATA...BROOKS AND NORTHERN KENEDY COUNTIES NORTHEASTWARD... OFFSHORE BUT VERY CLOSE TO THE COAST BETWEEN NORTH PADRE ISLAND AND THE BRAZORIA COUNTY COASTAL WATERS...THEN GENTLY ARCHING EASTWARD FROM THERE AT AN OBLIQUELY OFFSHORE ANGLE WITH RESPECT TO THE GALVESTON AREA. THIS BOUNDARY IS FORECAST TO DRIFT NORTHWARD THROUGH THE REMAINING PRE-DAWN HOURS...IMPAIRED SOMEWHAT BY CONVECTIVELY PRECIP-RELATED REINFORCEMENT OF STATIC STABILITY AND BAROCLINICITY TO ITS NORTH. HGX RADAR IMAGERY CONSISTENTLY HAS SHOWN EPISODIC MESOCYCLONES WITHIN A CLUSTER OF CONVECTION LOCATED OFFSHORE FROM BRAZORIA...GALVESTON AND CHAMBERS COUNTIES...ALONG AND NORTH OF THE VORTICITY-LADEN SURFACE FRONTAL ZONE. GIVEN ITS LOCATION IN THE STABLE AIR...WITH EAST-NORTHEAST SURFACE WINDS AND TEMPS IN THE 60S F...THE VERY LARGE HODOGRAPHS OF THE HGX VWP QUITE LIKELY OVERSTATE THE ACTUAL SRH AVAILABLE TO SURFACE-BASED CONVECTION INTERACTING WITH THE FRONT. NONETHELESS...0-1 KM SRH 200-400 J/KG IS POSSIBLE ALONG THE UPPER TEXAS COAST FRONTAL SEGMENT...WHERE IT UNDERLIES A DEEP...35-40-KT...SOUTHEASTERLY TO SOUTHERLY LLJ. THE LLJ SHOULD BE MAINTAINED THROUGH AT LEAST MIDMORNING WITHIN A BROAD WARM-ADVECTION ZONE...IN TURN RELATED TO MASS RESPONSE AHEAD OF A SLOW-MOVING UPPER CYCLONE OVER NORTHERN MEXICO. ROUGHLY 50 KT EFFECTIVE-SHEAR MAGNITUDES ALSO SHOULD BE MAINTAINED OVER THE AREA GIVEN ESSENTIALLY STEADY-STATE MID/UPPER-LEVEL FLOW. THOUGH MOST OF THE SURFACE-BASED CONVECTION SHOULD REMAIN OVER THE GULF...THAT MASS RESPONSE MAY ALLOW A SLIVER OF FAVORABLE WARM-SECTOR AIR (WITH MLCAPE AROUND 500-800 J/KG) TO REACH THE COAST BENEATH THE LLJ...ACCOMPANIED BY A MARGINAL TORNADO RISK. ..EDWARDS.. 12/03/2016 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LCH...HGX... LAT...LON 28639602 28949561 29529497 29699445 29619430 29579429 29419464 29369471 29319471 29119507 29039513 28819548 28679578 28639602 NNNN