B737-300 FO RPTS COMPANY'S COMPUTER SYS RETAINS FIELD CONDITION RPTS WELL BEYOND WHEN THEY ARE STILL ACCURATE AND TIMELY UPDATES ARE NOT ALWAYS FORTHCOMING.

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THIS RPT IS GENERAL IN NATURE. THE FLT LISTED ABOVE HAPPENS TO BE THE LAST TIME THE ISSUE CAME TO MY ATTN. THE SEATTLE WX THAT EVENING WAS A RAIN/SNOW MIXTURE WITH BELOW FREEZING TEMPS AT THE SURFACE. RWY PLOWING AND CHEMICAL TREATING WAS IN PROGRESS; AND PRIOR TO TOP OF DSCNT; A FIELD CONDITION RPT WAS REQUESTED VIA ACARS. THE RPT THAT WAS GENERATED BORE NO RESEMBLANCE TO ACTUAL FIELD CONDITIONS; FOR THE GOOD REASON THAT IT WAS 3 WKS OLD. I HAVE NOTICED THIS BEFORE. APPARENTLY ONCE A FIELD CONDITION RPT IS ISSUED; THE COMPUTER KEEPS IT IN MEMORY AND REGENERATES IT INDEFINITELY WHENEVER REQUESTED UNLESS A REPLACING FIELD CONDITION RPT IS ISSUED; SOMETIMES WKS OR MONTHS AFTER THE DAY IN QUESTION. VERY OFTEN NO REPLACING/CANCELING RPT IS ISSUED. UNDER SEPARATE COVER; I AM SENDING A PARTICULARLY EGREGIOUS EXAMPLE OF THIS: THE WX FOR IDAHO FALLS EARLIER THIS YR -- A FIELD CONDITION RPT LISTING THE RWY AS 'BARE AND DRY' WAS ISSUED ONCE DURING THE MONTH. OVER 2 WKS LATER; THIS WAS STILL BEING MERRILY PRINTED OUT WITH EACH WX REQUEST; AT THE SAME TIME AS THERE WERE NOTAMS LISTING ICE ON THE RWYS WITH MU METER READINGS AS LOW AS 22. IN THIS INSTANCE; THE ARPT AUTHS USED NOTAMS RATHER THAN A FIELD CONDITION RPT TO ADVISE OF THE RWY CONDITIONS; AND THE OLD FIELD CONDITION RPT WAS STILL IN OUR COMPUTER SYS. A FLT CREW INBOUND TO THE FIELD CALLING UP FIELD CONDITION INFO ON ACARS WOULD HAVE RECEIVED A RPT OF 'BARE AND DRY.' THIS IS; TO SAY THE LEAST; A SUB-OPTIMAL ARRANGEMENT. MAY I RESPECTFULLY SUGGEST THAT FIELD CONDITION RPTS BE AUTOMATICALLY ERASED 24 HRS AFTER ISSUE.