WordNet (r) 3.0 (2006):

unpredicted
    adj 1: without warning or announcement; "they arrived
           unannounced"; "a totally unheralded telegram that his
           daughter...died last night"- M.A.D.Howe [syn:
           unannounced, unheralded, unpredicted]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "unpredicted":
   abrupt, electrifying, extraordinary, hasty, headlong, impetuous,
   improbable, impulsive, more than expected, nerve-shattering,
   out-of-the-way, past expectation, precipitant, precipitate,
   precipitous, quick, shocking, speedy, startling, sudden,
   surprising, swift, unannounced, unanticipated, undivined,
   unexpected, unforeseeable, unforeseen, unguessed, unheralded,
   unhoped for, unlooked-for, unpredictable, unprepared for,
   without warning