AN LTT HOLDS FOR LNDG AT ROC; NY. WHEN THE WX REMAINS LOW THEY DIVERT TO THEIR ALTERNATE. FLC COMPLAINS THERE SHOULD HAVE BEEN ANOTHER ALTERNATE LISTED FOR GREATER RELIABILITY OF DIVERTING TO A USEFUL ARPT. THERE WAS A WAY TO LIST MORE THAN ONE ALTERNATE; BUT COM WAS LACKING BTWN FLC AND DISPATCH.

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I WAS THE CAPT OF A FLT THAT DEPARTED ROCHESTER; NY; ON OCT/XX/97. THE FO AND I RPTED TO WORK ON SCHEDULE AND I OBTAINED MY RELEASE AND WX FROM THE STATION PERSONNEL AT THAT TIME. WE COMPLETED OUR RUN-UP AND PROCEEDED BACK TO THE GATE FOR AN ON-TIME DEP. AFTER THE RUN-UP; THE FO INQUIRED ABOUT THE WX. I TOLD HIM THE ARR ARPT; WHITE PLAINS; WAS RPTING 1/4 MI VISIBILITY; BUT THE FORECAST CALLED FOR 2 MI VISIBILITY WITH OCCASIONAL 1 MI VISIBILITY. HE ASKED ME IF I WAS GOING TO CALL PLATTSBURG DISPATCH. I TOLD HIM NO; BECAUSE THE FORECAST WAS OK AND THEY WOULD ADVISE US TO GO. WHILE ENRTE; ATC ADVISED US THAT THE RVR AT WHITE PLAINS WAS DOWN TO 1200 FT. I TOLD THE FO TO CALL DISPATCH ON THE RADIO AND INFORM THEM OF OUR SIT. THEY ASKED US HOW MUCH FUEL WAS ONBOARD AND CONTINUE TO OUR DEST. APPROX 35 MI FROM THE ARPT; WE ENTERED A HOLDING PATTERN AND THE RVR AT THE ARPT WAS NOW 800 FT. I COMMENTED TO THE FO HOW THE WX SVC MISS FORECASTING THE FOG. AFTER HOLDING FOR 45 MINS; WE CONTACTED DISPATCH AND THEY INFORMED US TO DIVERT TO STEWART-NEWBURGH WHICH WE DID WITH NO TROUBLES. THE PROB THAT ARISES IS DISPATCH HAD AN AMENDED FORECAST FOR WHITE PLAINS WHICH HAD THE VISIBILITY FORECASTED TO BE 1/2 MI VISIBILITY AND OCCASIONAL 1/4 MI VISIBILITY. OUR RELEASE SHOULD HAVE BEEN AMENDED TO INCLUDE THE EXEMPTION WHICH WOULD HAVE REQUIRED AN ADDITIONAL ALTERNATE. OUR DISPATCH DID AMEND OUR RELEASE WHEN WE DIVERTED TO STEWART- NEWBURGH TO BE LISTED ON THE RELEASE.