The Topsfield Planning Board plans to discuss some elements of the medical marijuana laws Tuesday at a public hearing, but will likely put off the determination of zoning locations for medical marijuana centers. Community development coordinator Roberta Knight said that at its March 5 meeting, the board began a discussion about proposing an article for the May 7 annual Town Meeting for a temporary moratorium (likely for one year) as it awaits state Department of Public Health rules and regulations for medical marijuana use, which will be used to determine local zoning issues. Those regulations are expected to be delivered this spring. The board’s discussion is expected to continue at its April 2 meeting. At Tuesday’s meeting, the board will also hold a public hearing on modification of storm-water rules and regulations. The Planning Board meeting will take place at the Town Library, 1 South Common St., at 8 p.m.