  Let F be a p-adic field, W_F its absolute Weil group, and let k be an
algebraically closed field of prime characteristic l different from p. Attached
to any l-adic representation of W_F are local epsilon- and L-factors. There are
natural notions of families of l-adic representations of W_F, such as the
theory of Galois deformations or, more generally, families over arbitrary
Noetherian W(k)-algebras. However, the epsilon and L-factors do not interpolate
well in such families. In this paper it is shown that the gamma factor, which
is the product of the epsilon factor with a ratio of L-factors, interpolates
over such families.
