B737-800 CAPT REPORTS DISCOVERING ICE ON UPPER WING ROOT DURING PREFLIGHT AFTER LONG FLIGHT. NO PRECIPITATION WAS FALLING.

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INBOUND ACFT ARRIVED ON TIME AND AFTER TOWING FROM INTL TERMINAL I BOARDED ACFT AND BRIEFED FLT ATTENDANTS. UPON LOOKING THROUGH THE CABIN; I DID A CURSORY LOOK OUT THE OVERWING WINDOWS AND NOTICED A SHEET OF ICE ON BOTH WING ROOTS. I NOTIFIED MAINT AND THEY SENT A MECH OUT SEVERAL MINS LATER; WHO SHORTLY THEREAFTER DECLARED THAT ALL THE ICE WAS MELTED. FROM MY PREVIOUS EXPERIENCE ON THE MD80; AND KNOWING THAT ICE OF THOSE PROPORTIONS TAKES A WHILE TO MELT; I HAD A SUSPICION THAT THE ICE WAS STILL THERE. I DID ANOTHER CHK FROM INSIDE THE CABIN AND SURE ENOUGH THE SAME ICE SHEETS WERE STILL PRESENT. I NOTIFIED MAINT AND THEY SENT OUT THE MECH AGAIN; AND WE BOTH VISUALLY INSPECTED THE WING ROOT FROM THE CABIN. UPON SEEING THE ICE; THE MECH DECLARED THAT IT WAS GOING TO BE A 1.5 HR DELAY. THIS TURNED OUT TO NOT BE THE CASE; BUT IT POINTS OUT A SERIOUS DEFICIENCY IN THE ICE INSPECTION PROCESS FOR THE B737. 1) THE HIGHER WINGS ON THE B737 (ESPECIALLY THE NG'S) DO NOT ALLOW A GOOD VANTAGE POINT FOR THE MECHS TO VISUALLY INSPECT THE WINGS FROM THEIR EXISTING LADDERS. 2) THERE IS NO ANTI-SKID FEATURE FOR THE MECHS TO 'FEEL' A DIFFERENCE (OR NOT) AS ON THE MD80'S. 3) I THINK THERE IS A BELIEF THAT THIS IS AN MD80-ONLY PROB AND NOT AS MUCH A CONCERN FOR THE B737 FLEET. 4) FLT CREWS NEED TO TAKE THE TIME TO LOOK FOR THEMSELVES TO ENSURE THE WINGS ARE CLR. THIS ACFT CAME IN FROM A LONG FLT WITH EXTRA SUPER-COOLED FUEL (I ASSUME FOR ANTICIPATED ARR DELAYS) INTO A HUMID ENVIRONMENT. THESE CONDITIONS SHOULD TRIGGER A BRIGHT LIGHT IN EVERYBODY'S HEAD TO BE ON THE WATCH FOR THE POTENTIAL FOR WING ICING TO DEVELOP. I THINK WITH OUR LONGER RANGE FLTS THIS IS AN ISSUE MANY ARE NOT ADEQUATELY AWARE OF. FOR BOTH PLTS AND MAINT -- EMPHASIZE TO ALL CONCERNED TO BE AWARE THAT THIS IS A SERIOUS THREAT THAT DESERVES INCREASED ATTN.