The Collaborative International Dictionary of English v.0.48:

Forewarn \Fore*warn"\ (f[=o]r*w[add]rn"), v. t. [imp. & p. p.
   Forewarned (f[=o]r*w[add]rnd"); p. pr. & vb. n.
   Forewarning.]
   To warn beforehand; to give previous warning, admonition,
   information, or notice to; to caution in advance.
   [1913 Webster]

         We were forewarned of your coming.       --Shak.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "forewarned":
   agape, agog, all agog, anticipant, anticipating, anticipative,
   anticipatory, awaiting, certain, confident, eager, expectant,
   expecting, forearmed, forestalling, gaping, hopeful,
   in anticipation, in expectation, looking for, looking forward to,
   not surprised, optimistic, prepared, ready, sanguine, sure,
   unsurprised, waiting, waiting for, watching for