Sounds like your appraisal was done as part of probate. Appraisals are based on a point in time, and depending on the "use" of the appraisal, they may not be representative of what the house would actually sell for.
Your best bet is not to use a comparative market analysis as that would not stand up in court if contested. Consider getting a new appraisal from a licensed appraiser and make sure that you indicate your intended use is for "marketing" the home for sale. The appraisals for probate are typically done at the time of death for the decedent, and since probate typically takes a while, it's very likely your current appraisal is out of date. If more than 90 days has passed in your market, given the deterioration that has occurred of late, I think your appraisal is probably meaningless.
A new appraisal will probably run less than $400. Just be sure your siblings agree to the choice of appraisers, and don't use the one that did the probate appraisal.