(Portland, OR)  --  Safety concerns have led to the closure of all grass Portland Parks and Recreation sports fields through the weekend, as bad weather continues.  Officials say the closure affects grass fields at PP&R sites, as well as events permitted by the department at Portland Public Schools facilities.  However, all fields with synthetic turf will remain open.  The Parks and Recreation Department says the wet conditions present safety hazards, and use of the grass fields could impede efforts to maintain and care for them.