to stock up on something
maryam: have you seen the weather forecast?
francis: no, i've been too busy to watch tv today.
maryam: well, they're forecasting heavy snow from wednesday on. it could last for a few days.
francis: oh, no! i haven't done my weekly shopping yet.
maryam: you'd better get down to the supermarket as soon as you can.
francis: you bet. i'm going to stock up on essentials like bread and milk in case the snow lasts longer than expected.