These limber grades are governed by the amount of clear lumber which can be cut out of a board. Higher quality timber yields higher quality lumber - for a higher price. In addition, veneer from high quality timber adds additional value. There is little government intervention that supplements lumber supply and demand in the North East United States. Lumber prices will rise and fall as determined by the free market.
Weather can cause disruption in the log supply and it can be very localized.
Heavy snow or rain can curtail logging in any area. This disruption will affect the amount of logs that are available to be milled. If market prices are suppressed due to demand, mills will curtail operations to reduce inventory backlogs at the mill. If timber is scarce, mills will have no need to increase production capacity. If production capacity is static, lumber prices will rise when demand isn't met.