ERRONEOUS ASOS PREVENTS THE ISSUANCE OF A VISUAL APCH CLRNC TO AN SMT.

Narrative

ON THE FLT LISTED ABOVE; THE ACFT DSNDED THROUGH THE CLRNC ALT WHILE APCHING THE ARPT. THE DEV OCCURRED DURING A DISCUSSION WITH ATC (GEG APCH) ABOUT AN APCH CLRNC. WHILE DSNDING; BUT BEFORE REACHING THE CLRNC ALT; THE ACFT DSNDED INTO VMC CONDITIONS (5000 FT OVCST AND 15+ MI VISIBILITY). THE ARPT WAS ACQUIRED VISUALLY AT A DISTANCE OF 12 MI. THE CTLR REFUSED TO ISSUE A VISUAL APCH CLRNC DUE TO THE ASOS RPT OF 2 MI VISIBILITY AT THE ARPT. WHILE THIS DISCUSSION ENSUED; THE ACFT DSNDED BELOW THE CLRNC LIMIT. THE DSCNT WAS NOT ARRESTED BECAUSE I; THE PIC; ANTICIPATED A CLRNC FOR A VISUAL APCH DUE TO HAVING THE FIELD IN SIGHT IN VFR WX. THIS HAS BEEN SOP FOR THE 4 YRS THAT I HAVE OPERATED OUT OF THIS ARPT. WHEN THE VISUAL APCH CLRNC WAS DENIED; THE APCH CTLR REQUESTED THAT THE ACFT CLB BACK TO THE PROPER ALT. WHEN THE FLT WAS 3 MI E OF THE MSO VOR; THE FLT WAS HANDED OFF TO THE TWR. WHEN THE TWR WAS INFORMED OF THE VISUAL CONTACT WITH THE ARPT; A CLRNC FOR A VISUAL APCH WAS ISSUED. THIS CLRNC WAS CANCELED WHEN THE TWR CTLR WAS REMINDED OF THE 'RPTED' VISIBILITY. WHEN THE FLT REACHED THE VOR; THE CTLR CLRED THE FLT TO ENTER THE PATTERN AND LAND. AFTER LNDG; THE TWR CTLR DISCUSSED THE RPTED VISIBILITY WITH ME AND STATED THAT THE ASOS WAS OFTEN INACCURATE. I FEEL THAT THE BLIND TRUST IN THE ASOS SYS OVER THE RPT OF EXPERIENCED PLTS AND CTLRS IS ONE CONTRIBUTING FACTOR TO THIS INCIDENT. THE FACT THAT THE RPT OF THE ASOS WAS ERRONEOUS SHOULD HAVE BEEN CONSIDERED BY THE CTLRS. ANOTHER FACTOR IN THIS INCIDENT WAS THE PAST HISTORY OF HAVING A CLRNC FOR A VISUAL APCH BEING ISSUED IN THIS SIT.