Restore server instance using logical backup and wal files
Yes it is possible the logical backup will be having data before failover say u took it on 3pm it will have complete data till 3pm 

And suppose you fail-over the master say on 4 pm the wal-files will have records of changes done from 3pm to 4pm.

So just create a postgresql instance with help of pg_createcluster 
and inserted the dump file first.

then copy the wall files to /var/lib/postgresql/9.1/main/pg_xlog/ 
path which is default path for most postgresql installation.
then finally 
restart the services service postgresql restart