Zarun gives each of you a bandoleer full of potions (healing, enlarge for the fighter-types, etc), and you leave. After some more preparations, Barnak teleports everyone to spot that had been chosen.
From cover on the mountain, you can see the seige. Things are looking slightly better than reported. Silverymoon is located in the middle of a very large river, small in diameter but built quite vertically. The city has force bridges which are about 100 feet long each, which connect it to the banks. Obviously, they are presently deactivated. It also has the most powerful known Mythal remaining on Faerun, which blocks the enemy from entering, prevents most harmful magic from coming in (death magic, evocation, summoning, evil) or being used without the proper authorization, and provides a number of minor magics for the cities defenders. The forces inside include over 50 L8-13 military individuals and at least as many equally powerful civilians, and about 1,000 military personal overall. Alustriel, the archwizard who ruled the city, disappeared recently, but the High Mage of Silverymoon, Taern Hornblade (Evoker18) remains in charge.
While the further cities of the Lords' Alliance have yet to send forces, about 6,000, mostly human with a very large number of dwarves, are arrayed on the opposite side of the river from the enemy army.
The enemy is more numerous even than the defenders, however, numbering 10,000 or more. While their evocation magic is ineffective and they apparently havent figured out how to penetrate the wards physically yet, their arrows, catapults, cannons, boulders, and that giant, firey-rock-blasting thing periodically assault the city. Hundreds of workers are cutting down trees, building raft bridges, and breaking rocks off the mountainside for the giants, seige engines, and the aformentioned giant, firey, rock-blasting creature.
The fact that they are building the bridges to put on the river is a bit disturbning. That could be a sign that they have a way through.
The group of command tents is towards the back of the camp, with only the workers in between you and them. The supplies stream in two trails on either side of them up to the seige engines. Beyond the command tents are rows and rows of arrayed armies, with the cannon-beast in the center of everything.
The command tents contain at least a dozen ogre and giant guards, as well as a few other assorted leaders of lesser types.