* WHAT...Heavy lake effect snow. Additional snow accumulations between 5 and 8 inches. Amounts near 12 inches are possible over northern Warren County. * WHERE...McKean and Warren Counties. * WHEN...Until 7 PM EST Thursday. * IMPACTS...Travel will be very difficult at times. The hazardous conditions could impact the evening and Thursday commutes. * ADDITIONAL DETAILS...Heavy snow bands will drift south into the region later this evening, significantly ramping up the snow accumulation and greatly reducing this visibility at times to below one quarter of a mile. Wind chills will be near zero later tonight and Thursday.