The Collaborative International Dictionary of English v.0.48:

Supernal \Su*per"nal\, a. [L. supernus, from super above: cf. F.
   supernel. See Super-.]
   1. Being in a higher place or region; locally higher; as, the
      supernal orbs; supernal regions. "That supernal judge."
      --Shak.
      [1913 Webster]

   2. Relating or belonging to things above; celestial;
      heavenly; as, supernal grace.
      [1913 Webster]

            Not by the sufferance of supernal power. --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

supernal
    adj 1: being or coming from on high; "interpret the plague as a
           visitation from heaven, a supernal punishment for the
           sins of men" [ant: infernal]
    2: of heaven or the spirit; "celestial peace"; "ethereal
       melodies"; "the supernal happiness of a quiet death" [syn:
       celestial, ethereal, supernal]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "supernal":
   Elysian, Olympian, aerial, airy, altitudinous, ascending, aspiring,
   beatific, beatified, blessed, celestial, colossal, dominating,
   elevated, eminent, ethereal, exalted, extramundane,
   extraterrestrial, from on high, glorified, haughty, heavenly, high,
   high-pitched, high-reaching, high-set, high-up, in glory, lofty,
   monumental, mounting, otherworldly, outtopping, overlooking,
   overtopping, paradisaic, paradisal, paradisiac, paradisic,
   prominent, soaring, spiring, steep, sublime, superlative, topless,
   toplofty, topping, towering, towery, transcendental, transmundane,
   unearthly, unworldly, uplifted, upreared