ms duck, think you might be a little low on your power estimates, if only because any magic emanating from Mab (either by choice or by happenstance) should have been grounded by the water (ie the big damn lake). so any cold front would actually require much more energy (Im remembering molly and the fog and the fairies on jet-skies). I see it this way: if the cold front would usually take some amount of energy to create, and water counteracts this (both due to "leaching" the magic away and due to the high specific heat of water) Mab would have to use some amount of magic in serious excess to any calculation. we know that fairies are limited in their magic in/on/around water (see the above mentioned fog incident with the fairy assassins). Anyway, just my two cents.