Choosing a departure window

By Tyler Wilson · September 2026

A departure window is good when four things hold at once: forecast wind and seas stay inside your boat and crew limits for the whole run, not just the start; the current works with, or at least does not fight, the legs where it matters; daylight covers the trip with margin; and no active marine warning touches your water. Pick the window first and fit the trip to it, not the other way around.

The window is a whole-run question

The most common mistake is reading the forecast for the hour you leave the dock. A five-hour run meets five different forecast hours, and the one that bites is usually the last one, when you are furthest from home, the crew is tired, and the afternoon wind has filled in. Check the forecast at each leg’s estimated time, not the marina’s morning.

Mornings usually beat afternoons on protected water. Daytime heating drives afternoon wind in most Pacific Northwest summer patterns, and we have run enough early Jervis Inlet mornings to trust glassy water at 0700 that turns to whitecaps by 1500. That is a pattern, not a rule: the forecast for your hours is the authority.

Current sets the gates

On tidal water, some parts of a route only make sense at certain stages of current: a rapids at slack, a long channel with the flood behind you, an inlet entrance before the wind turns against the ebb. Treat those as fixed gates and build the window backward from them. Timing beats horsepower: we learned to run Malibu Rapids on the tide in a light, well-powered boat, and knowing the gate mattered more than the power did.

The checklist

Check	What good looks like
Wind at each leg's ETA	Sustained and gusts inside your crew's limit for every hour of the run, with the trend flat or easing
Seas and period	Height inside your limit and a period long enough that the ride is a ride, not a pounding
Current at the gates	Slack or favorable at rapids, entrances, and long channels; never wind against a strong ebb at an exposed mouth
Warnings and advisories	Nothing active or forecast for your zones during the window
Daylight	Departure and arrival in daylight, with an hour of margin at the far end
The bailout	A place to duck into partway, and the conditions to reach it, if the forecast is wrong

Try a window

A sample summer day, hour by hour. Set your crew’s limits and watch the window open and close: solid hours are inside your limits, hollow hours are not.

Wind limit: 15 kn

Seas limit: 3 ft

Your window: 0500 to 1200, 8 hours. It closes at 1300, when the wind tops your limit.

A sample day, not a forecast. The lesson is the shape: the window is the hours the whole read stays inside your limits, not the hour you leave the dock.

Margin is part of the window

A window that only works if everything goes right is not a window. Add margin three ways: leave earlier than the math requires, hold a fallback anchorage or harbor partway, and decide before departure what forecast change would turn you around. Deciding at the dock is easy; deciding in building seas is not.

Sources

Planning, not navigation

Everything on this page is homework for before you leave the dock. Plan here; navigate on your charts and your plotter. And what the water is actually doing always outranks a forecast, this page included.

TidePilot is a planning advisor, not a navigation system. Always confirm conditions with current observations and use a marine chartplotter for navigation underway.

Where TidePilot comes in

Everything on this page is the homework a TidePilot brief does for your specific boat, route, and crew. Share a start and a destination and the brief comes back with the read at each leg's arrival time, your wind and sea limits applied, and the reasoning shown. The call stays yours. Start a brief.

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