SOUTHEAST TEXAS FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 239 AM CDT WED OCT 22 1997 RAPID WEATHER CHANGES ON THE WAY FOR SE TX. AT 05Z...WEAK COLD FRONT EXTENDED FROM CENTRAL LA TO JUST NORTH OF CRP TO NORTH OF LAREDO. WIND SHIFT AND DRIER AIR WERE ASSOCIATED WITH THE FRONT. INTERESTING FEATURES NOTED ON SATELLITE...EXTENSIVE LOW CLOUD DECK DEVELOPING OVER NE TEXAS CONTINUES TO SINK S AND SW. A STRONG SURGE OF PACIFIC MOISTURE IN THE SUBTROPICAL JET (STJ) IS STREAMING TOWARD SOUTH TEXAS AND EXPECT THESE TWO AREAS OF CLOUDS TO MERGE OVER SE TX AND KEEP SKIES CLOUDY TODAY. A FEW S/WVS IN THE STJ MAY PRODUCE A FEW -SHRA OVER MAINLY SOUTHERN PORTIONS OF FA. CLOUDS WILL KEEP TEMPS LOWER TODAY AS PREVIOUS FCST NOTED. THINGS CHANGE LATE TONIGHT INTO THURSDAY. AS UPPER LOW PRESSURE OPENS UP OVER THE SOUTHWEST U.S. AND SHIFTS EASTWARD...LOW LEVEL WINDS WILL BECOME EAST..THEN SE AND INCREASE TO 15 TO 20 KTS. LOW LEVEL MOISTURE WILL INCREASE RAPIDLY. WOULD NOT BE SURPRISED IF TEMPS ACTUALLY WARMED WED NITE IN RESPONSE TO RETURN FLOW. WEAK COLD FRONT OVER S TX WILL RETURN NORTH AS A WARM FRONT THURSDAY. ATTM...IT LOOKS LIKE THE FRONT WILL LIE ACROSS PORTIONS OF SE TX. A STRONG VORT MAX WILL APPROACH THE FA THURSDAY AFTERNOON ENHANCING LIFT. TSRA WILL LIKELY DEVELOP LATE MORNING OR EARLY AFTERNOON AND ORGANIZE INTO A SQUALL LINE AS IT MOVES ACROSS SE TX. INGREDIENTS COMING TOGETHER FOR A POTENTIALLY SERIOUS (SEVERE) WX EVENT. A SPLITTING JETSTREAM...A 110 KT 250 MB SPEED MAX EMBEDDED IN STJ...A 30 TO 40 KT LLJ...MID LEVEL DRY AIR INTRUSION AND A 30H CIRCULATION WILL INTERACT TO PRODUCE TSRA ACROSS THE AREA. VERTICAL WIND PROFILES INDICATE SUFFICIENT SPEED AND DIRECTIONAL SHEAR TO PRODUCED SUPERCELLS AND POSSIBLE TORNADOES. WOULD LIKE SEVERE MENTIONED IN ALL ZONES FOR THURSDAY...HOWEVER THE GREATEST THREAT FOR SVR WX WILL BE OVER THE NORTH HALF OF SE TX. WEST WINDS WILL BUILD IN BEHIND THIS SYSTEM AND FRIDAY LOOKS TO BE DRY AND ON THE WARM SIDE AS COMPRESSIONAL HEATING FROM SINKING AIR BEHIND THIS SYSTEM ENTERS THE AREA...THEN COOLER FOR THE WEEKEND. SPS FOR THURSDAYS SEVERE WX THREAT WL BE ISSUED BY 10Z. PRELIMS... CLL E/E E/A 071/059 077/059 -172 NE E/E E/B 070/058 077/059 -183 IAH E/E E/B 072/060 077/059 -273 GLS E/E E/A 073/064 075/062 -262 3RD PD ALL ZONES...MAINLY AFTN SHRA/TSRA - SOME POSSIBLY SVR 43/42