Freeze-thaw and why it matters
Water that gets into even a small gap in flashing, sealant or shingle overlap expands by roughly nine percent when it freezes, which is enough to widen a small crack a little more with every cycle. A Centre County winter can run through dozens of freeze-thaw cycles between November and March, and each one takes a tiny problem and makes it slightly worse, which is why a leak that seemed minor in December can be significantly bigger by the time March arrives.
This is part of why we check flashing and sealant details even during a routine inspection outside of storm season. A gap that looks harmless in October has a whole winter of freeze-thaw ahead of it.
Ice damming at the eaves
Heat escaping from a poorly insulated or poorly ventilated attic melts the snow directly above the warm section of roof, and that meltwater runs down and refreezes once it reaches the colder eave overhang, where there is no warm attic space underneath it. Over time this builds a dam of ice that backs water up under the shingle courses above it, and that backed-up water finds its way through nail holes and seams that were never designed to handle standing water.
Proper attic insulation and ventilation are the actual fix for repeated ice damming, not more roof cement at the eave each spring. Ice-and-water membrane at the eaves provides a backup layer of protection, but it works best alongside a properly ventilated attic rather than as a substitute for one.
Snow load, especially at higher elevation
Properties at higher elevation toward Philipsburg and up the slopes near Boalsburg see heavier and longer-lasting snow accumulation than the valley floor around State College itself, and that extra weight matters most on older roofs where the decking has already been weakened by a prior leak. A structurally sound roof handles a typical Centre County snow load without concern, but a roof with existing rot in the decking is a different situation, which is part of why the attic inspection matters as much as the surface condition of the shingles.
What to watch for during the season
Icicles along the eave are not automatically a problem on their own, but a thick ridge of ice building up at the roof edge, especially paired with water stains appearing on an interior ceiling, is worth a call before it gets worse. The same goes for any noticeable sagging along the roofline after a heavy snowfall, which should be looked at promptly rather than waiting for the snow to melt on its own.