ACR CAPT REPORTS JAC AWOS EXTREMELY WEAK AND NEARLY UNREADABLE.

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COULD NOT OBTAIN AWOS DATA FOR APCH ON TWR OPERATING AWOS FREQ. AUDIO WAS TOO WEAK. I LATER SWITCHED TO THE TWR CLOSED AWOS (AS TWR WAS NOW CLOSED FOR THE NIGHT) AND AGAIN FOUND THE AUDIO UNUSUALLY WEAK/UNUSABLE. ASKED SLC ARTCC WHAT WAS RWY IN USE AND WAS TOLD RWY 19. CTLR GAVE ME WX BUT STATED 'IT WAS OLD; OVER ONE HR OLD.' THAT MOST RECENT WX RPT PLUS VMC CAUSED ME TO BELIEVE THAT OBTAINING A MOST RECENT WX RPT WAS REALLY JUST A 'PAPERWORK' FORMALITY. WE WERE STILL COMMITTED TO FLYING AN ILS RWY 19. AS WE PROCEEDED CLOSER TO JAC I KNEW I WAS NOT COMPLYING WITH THE FAR THAT REQUIRES A CURRENT WX RPT. SO I TRIED YET AGAIN AND FINALLY WAS ABLE TO BARELY COMPREHEND AN EXTREMELY WEAK; ALMOST UNUSABLE AUDIO AWOS ON 120.62 TWR CLOSED FREQ. GUESS WHAT? THE WINDS WERE OUT OF THE N AT 11 KTS! WE THEN TOLD SLC ARTCC THAT WE NEED THE VOR 1 FOR LNDG N. THE REST OF THE FLT WAS UNEVENTFUL. 2 OUTCOMES: 1) I CALLED THE FLT DISPATCH MGR BEFORE THE NEXT FLT TO DEPART FOR JAC AND TOLD HIM THAT THE TWR CLOSED AWOS WAS NEARLY UNUSABLE AND THE NEXT CREW NEEDS AN ALERT. I URGED THE DISPATCH MGR TO ALSO HAVE THAT PARTICULAR AWOS INSPECTED/INVESTIGATED. 2) JUST WHEN YOU THINK YOU CAN SLIDE BY WITH A 'MINOR' FAR VIOLATION; DON'T EVEN THINK OF IT. MY GUILTY CONSCIENCE PUSHED ME TO CHK THE AWOS ONE LAST TIME; AND LO AND BEHOLD; IN DOING SO IT SAVED US FROM A NASTY SURPRISE; OR WORSE.