Identify the total weight of shipments transported to San Mateo, California, in 2016.
"San Mateo" is the city_name; in 2016 refers to Cast(ship_date as DATE) = 2016
SELECT SUM(T1.weight) FROM shipment AS T1 INNER JOIN city AS T2 ON T1.city_id = T2.city_id WHERE T2.city_name = 'San Mateo' AND STRFTIME('%Y', T1.ship_date) = '2016'