PLT OF A C414 DECLARED MINIMUM FUEL ENRTE TO THE SECOND ALTERNATE ARPT AFTER 2 ARPT DIVERTS DUE TO WX.

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MISSED APCH AT INTENDED DEST. DIVERTED TO FILED ALTERNATE AND MISSED APCH AT ALTERNATE DUE UNFORECAST HVY SNOW. WAS REQUIRED TO DIVERT TO THIRD ARPT. DECLARED MINIMUM FUEL WHILE ENRTE TO THIRD ARPT. THE PROB AROSE WHEN I ENCOUNTERED MUCH LOWER THAN FORECAST WX AT BOTH DEST (OLE) AND ALTERNATE (BFD). ALTHOUGH I HAD LEGALLY REQUIRED FUEL RESERVE AFTER MISSED APCH AT BFD; REMAINING FUEL WAS MINIMUM NECESSARY TO DIVERT TO THIRD ARPT AND EXECUTE REQUIRED APCH THERE. DECLARED MINIMUM FUEL AS A PRECAUTION AND TO REQUEST EXPEDITED HANDLING FROM ATC. LANDED AT JHW WITH LESS THAN 30 MINS FUEL REMAINING. JUDGEMENT ERROR OCCURRED WHEN CHOOSING AN ALTERNATE THAT WAS ONLY 30 NM FROM PRIMARY DEST AND NOT CONSIDERING THAT BOTH ARPTS WOULD LIKELY BE SUBJECT TO SAME WX (BETTER OR WORSE). EVEN THOUGH FUEL PLANNING WAS PER FAR; SHOULD HAVE ADDED ADDITIONAL RESERVE FUEL FOR ADDED SAFETY MARGIN. WHILE THE FLT WAS COMPLETED UNEVENTFULLY; I CONSIDERED THE PREFLT PLANNING TO HAVE BEEN INADEQUATE WITH RESPECT TO THE POTENTIAL FOR UNFORECAST ADVERSE WX.