UPDATE December 10th, 2020, please also see: https://www.odoo.com/documentation/user/14.0/db_management/hosting_changes.html 

Generally it is.  Please try these steps.

1. Plan a time to do this after the weekly update of Odoo.sh, and update your On Premise Enterprise server to the lastest daily build of Odoo.  This is important.  Odoo.sh is updated at the start of each week and the code on your Enterprise Server needs to be similarly updated.  You need to make sure the same custom code repositories are available on your enterprise server as are available to your Odoo.sh database.  This means cloning the same GITHUB repository on your Enterprise machine.  Note that your GITHUB repository won't be deleted if you delete the Odoo.sh Project.

2. Take a backup from the BUILDS tab of your Odoo.sh database:

Select EXACT DUMP and WITH FILESTORE.

3.  On your Odoo Server matching the same release as your Odoo.sh database, restore it:

Select THIS DATABASE WAS MOVED.

4. Find the BASE module and upgrade it: