Small Craft Advisory: what it means for a coastal sailor
A Small Craft Advisory is a US National Weather Service notice about conditions that may be hazardous to smaller vessels in a named marine area. It is a reason to examine the forecast and your boat's limits closely. It is not a worldwide wind-speed rule, and the words “small craft” do not refer to one legally fixed boat length.
The National Weather Service marine FAQ says advisory thresholds vary by geographic area. Wind, waves and, in some places, hazardous ice can lead to an advisory. The skipper's experience and the vessel's type, size and seaworthiness also matter. Sailors outside the US should use the warning terms and instructions issued by their own maritime authority.
Read the area and time before the headline
An advisory applies to the waters and time shown in the notice. Start with the named forecast zone, its start and end times, and the expected wind or sea conditions. Then compare that area with your intended departure point, passage and destination. Conditions may also change while a trip is under way, so check the most recent official update before leaving.
Do not assume a notice for a neighbouring zone describes your route exactly. Likewise, the absence of an advisory at one point does not mean every part of a passage is comfortable or suitable for your vessel. Official zone forecasts, point forecasts, observations and local notices each answer a different part of the question.
Does a modest wind forecast mean the sea is safe?
No. A wind number on its own leaves out wave systems and local effects. The National Weather Service explains that a reported sea height is generally a *significant wave height*: an average of the highest third of waves, so individual waves can be higher. Wave period, current and shallow water also affect how conditions develop and how a vessel handles them. Read the NWS explanation.
That is why MARLOG's Home sailing window deliberately shows wind only. It highlights stronger wind in a 12-hour view, but it cannot turn wind bars into a departure recommendation. Open the wider MARLOG Forecast to inspect waves and other available conditions for a chosen point, then check the official marine forecast and warning for the operating area.
What should I check before deciding?
- Read the current official advisory and the forecast zone it names.
- Check the timing against the whole intended trip, including the return.
- Review wind, gusts, waves and local effects, not only a single hourly number.
- Consider the boat, crew and alternatives if conditions worsen.
- Recheck official updates and observations close to departure.
These checks support a decision; they do not replace local rules, a skipper's judgement or required safety equipment. The NWS marine forecast portal is the starting point for US waters. Elsewhere, use the responsible national or local service.
MARLOG can help you inspect wind, waves and currents at a chosen location while learning what the numbers mean. See MARLOG Forecast or get MARLOG for iPhone.
Sources: US National Weather Service marine FAQ; NWS significant wave height explainer; NWS marine forecast portal. MARLOG product details were checked against its Forecast page on September 22, 2026.