  Lattice cohomology, defined by N\'emethi in (arXiv:0709.0841), is an
invariant of negative definite plumbed 3-manifolds which conjecturally computes
the Heegaard Floer homology HF^+. We prove a surgery exact triangle for the
lattice cohomology analogous to the one for HF^+. This is a step towards
comparing these two invariants.
