The WGA walkout goes into effect at 12:01 a.m. on Monday, the WSJ is now posting. Picketing at the major movie studios and networks would begin later in the day. Both the writers and producers are holding out a very small chance of weekend talks that could be productive enough to avoid a walkout. But unless both sides are about to make some serious concessions - and they're not - we'll see a work stoppage. No mention at today's WGA news conference on which studios/networks will be picketed.
Updated post