J. Crew sister label Madewell has won the hearts and wallets of many with its booming ecommerce business, and now SF shoppers can try before they buy the hipster-prep apparel. Madewell opens its first Bay Area location in the Westfield Centre tomorrow, and the shop will fête its arrival Thursday from 6 to 8 p.m. with delicious snacks from Le Truc, drinks from some favorite local watering holes, and a DJ spinning stylish tunes. Better yet, the shop is also offering Madewell mailing list members 15 percent off all jeans through July 25. To attend, RSVP by email or sign up on Facebook.