Mooring overnight at Trellis Basin requires two checks
Trellis Basin sits behind a narrow throat that drains hard on the back half of the ebb. If you plan to moor overnight, you need to clear two separate gates: the harbor master's availability board and the actual water under your keel.
The four o'clock posting
The basin holds fourteen moorings. The harbor master updates the chalkboard outside the fuel dock at 1600 sharp. Any mooring marked with a single white stripe is available for transient use that night. Most summer evenings you'll see two or three open. By mid-July, one.
The board does not take reservations. You confirm the mooring by radio once you're inside the basin. That means you need to be through the throat before the window closes, which brings us to the second check.
Entry window: two hours either side of high
The throat carries six feet at high water, sometimes seven if the moon is right. Two hours before high and two hours after, most cruising keels clear without trouble. Outside that window the bottom comes up fast. I've watched boats touch at three hours past high in August when the spring tides were running weak.
The practical implication: if high water is at 1730, your entry window closes at 1930. But the availability board doesn't post until 1600. That leaves you three and a half hours to check the board, return to your boat if you're ashore, and make the approach.
Sounds comfortable. It is not.
The arithmetic tightens in the afternoon
Say high tide falls at 1500. Your window runs from 1300 to 1700. The board won't be updated until 1600, which gives you one hour to enter. If you're anchored outside the harbor or tied at one of the day slips near Prescott Dock, that hour disappears quickly.
I've seen crews motor past the fuel dock at 1605, read the board from the cockpit, then turn straight into the throat with twenty minutes of depth left. It works if you know the channel. If you don't, you'll spend the night somewhere else.
Checking before you commit
The harbor master will not answer questions about overnight availability before four o'clock. The VHF stays quiet on that subject. You can walk up to the fuel dock earlier in the day and look at yesterday's board, but it won't tell you anything useful about tonight.
Some crews call it planning. I call it a lottery with a two-hour ticket window.
If your arrival tide is late afternoon, you're fine. If it's morning or midday, you'll need to decide whether to wait around or move on. The basin is worth the wait if you want a quiet night with no roll and access to the dinghy dock. It is not worth missing your weather window for the next leg.
What to do if you miss both
If the board shows no availability or the tide has already turned against you, the outer anchorage off Salter Pier holds well in anything but a southeast blow. You'll roll a bit, but the holding is good and you're still inside the breakwater.
The basin is not the only overnight option in the harbor. It is simply the one that requires you to solve two problems in the correct order, on someone else's schedule, with no margin for delay.