The answer to 'why is my underlayment wind damage' is that your roof underlayment is likely damaged due to high winds or a severe storm. Underlayment is the protective layer installed beneath the roof shingles, and it can be vulnerable to wind damage if not properly installed or if it is older and deteriorating.
Some common causes of wind-damaged underlayment include: insufficient fastening, poor quality underlayment material, old or worn underlayment, and extreme weather events like hurricanes or tornados. Symptoms may include visible tears, lifting, or missing sections of the underlayment. If left unrepaired, wind-damaged underlayment can lead to leaks and further roof damage.