DOCS-460 correction

Author: Sam Kleinman

source/reference/mongodump.txt

@@ -187,6 +187,17 @@ Options
       in the ``_id`` index.
    2. Your database uses a custom ``_id`` field.
 
+   When you run with :option:`--forceTableScan`, :program:`mongodump`
+   does not use :operator:`$snapshot`. As a result, the dump produced
+   by :program:`mongodump` can reflect the state of the database at
+   many different points in time.
+
+   .. warning:: Use :option:`--forceTableScan` with extreme caution
+      and consideration.
+
+   operations 
+
+
 .. _mongodump-behavior:
 
 Behavior