WWJP74 RJTD 171800 IMPORTANT WARNING FOR OTARU NAVTEX AREA 171800UTC ISSUED AT 172100UTC WARNING(DENSE FOG) SEA OFF SOUTHERN COAST OF MARITIME PROVINCE POOR VIS 0.3 MILES OR LESS IN PLACES WARNING(ICING) SEA WEST OF SAKHALIN, SEA WEST OF HOKKAIDO NXT WARNING WILL BE ISSUED BEFORE 180300UTC =