How to survive server restart with sequelize postgres database and migrations

In my express application I use Sequelize to manage the database. Here's my bootstrap code.

db.sequelize
  .sync({ force: true})
  .complete(function(err) {
    if (err) {
      throw err[0];
    } else {
       //seed
       require('../db/seed')(db);
        app.listen(app.get('port'), function() {
          console.log('express listening on ' + app.get('port'));
        });
    }
});

As you can see, everytime I start the server first I seed the database with hard coded data.

Here's the code to initialize sequelize:

if (process.env.NODE_ENV === 'test') {
  console.log('[test] using in memory database');
  sequelize = new Sequelize('marbles-site-db', null, null, {
    dialect: 'sqlite',
    storage: ':memory:'
  });
} else if (process.env.HEROKU_POSTGRESQL_WHITE_URL) {
  var match = process.env.HEROKU_POSTGRESQL_WHITE_URL
                .match(/postgres:\/\/([^:]+):([^@]+)@([^:]+):(\d+)\/(.+)/);

  sequelize = new Sequelize(match[5], match[1], match[2], {
    dialect: 'postgres',
    protocol: 'postgres',
    port: match[4],
    host: match[3],
    logging: true // false
  });
} else {
  sequelize = new Sequelize('marbles-site-db', null, null, {
    dialect: 'sqlite',
    storage: './db/development.sqlite'
  });
}

As you can see, I use SQlite with flat file as storage for development and Postgres for production.

The problem is each time I restart the server, data in the database are gone. This is the case with SQlite, I suppose it's the same with Postgres too.

So what do I have to do to keep the data in the database even though I restart the server, and is this related to database migrations?

Note that the seed should not be needed after the initial boot.