For nominating EXXX as your alternate, you have to go one-up from the best avaliable approach. Ie, you say CAT1 is avaliable, you then have to have localiser minima (which is cieling+vis/rvr) or better to nominate. (If you had CATII you would have to have cat1 minima (which is vis/rvr ONLY, not the difference))
At least where I work, cieling is considered to be BKN, OVC or VV. Do note, again, that this is only relevant for non-precision approaches, but that IS relevant in this case, because of the requirement to one-up your alternate
Edit: so to answer your question; unless localiser minima is lower than 349'/7000m vis, you cannot use EXXX as an alternate. And while we're at it: what are your policies on TEMPO, BECMG, PROB30, PROB40 and TEMPO SH for destination/alternate planning, gentlemen?