The marine headline ladder
Definitions are from NWS Instruction 10-303. The last column is what Boat or Nope does when that headline is in effect for your marine zone.
| Headline | What triggers it | Boat or Nope call |
|---|---|---|
| Marine Weather Statement | Details on significant conditions not covered by another warning | Caution |
| Dense Fog Advisory | Visibility at or below a regional limit no greater than 1 nautical mile | Caution |
| Small Craft Advisory | Eastern Region: 25-33 kt sustained or frequent gusts (20-25 kt in some harbors and bays) and/or seas of 4-7 ft or more | Caution at best |
| Brisk Wind Advisory | A small craft advisory issued for ice-covered waters | Caution |
| Gale Watch | Increased risk of 34-47 kt winds, timing or location still uncertain | Caution |
| Gale Warning | Sustained winds or frequent gusts of 34-47 kt, not from a tropical cyclone | No-Go |
| Storm Warning | Sustained winds or frequent gusts of 48-63 kt, not from a tropical cyclone | No-Go |
| Hurricane Force Wind Warning | Sustained winds or frequent gusts of 64 kt or more, not from a tropical cyclone | No-Go. Stay in port. |
| Hazardous Seas Warning | Wave heights and/or steepness meeting local warning criteria | No-Go |
| Heavy Freezing Spray Warning | Ice building up at 2 cm per hour or more (0.7 cm/hr in Alaska) | No-Go |
| Special Marine Warning | Usually 2 hours or less: thunderstorm winds or gusts of 34 kt or more, hail 3/4 inch or larger, and/or waterspouts | No-Go |
Tropical storm and hurricane watches and warnings come from the National Hurricane Center and take priority over other marine headlines when a tropical system threatens.
Small Craft Advisory: the one you will see most
The Coast Survey warning page says there is no precise definition of a small craft. Any vessel that could be adversely affected should consider itself one. Operator experience, vessel type, size, and seaworthiness all matter.
Criteria vary by region. In the Eastern Region, which covers Maine to South Carolina plus Lakes Erie and Ontario, it is 25 to 33 knots of sustained wind or frequent gusts, with a lower 20 to 25 knot threshold for some lakes, harbors, and bays, and/or seas of 4 to 7 feet or more depending on the area. The NWS counts gusts as frequent when they last more than about two hours in a 12-hour forecast period. An advisory can be raised for gusts even when the sustained wind is below 25 knots.
A real example: on Friday, October 16, 2026, NWS Boston extended a Small Craft Advisory for Buzzards Bay, Vineyard Sound, Nantucket Sound, Rhode Island Sound, and Block Island Sound until 8 AM Sunday. The forecast called for northwest winds 15 to 25 knots with gusts up to 30 knots and seas 3 to 5 feet, and a Gale Watch was cancelled in the same message. A sustained wind of 15 to 25 knots sounds borderline. Gusts to 30 and 3 to 5 foot seas in a shallow bay do not.
The NWS advice that comes with a Small Craft Advisory: inexperienced mariners, especially those operating smaller vessels, should avoid navigating in hazardous conditions.
Gale, storm, and hurricane force
These three are wind warnings, defined by sustained wind or frequent gusts.
- Gale Warning: 34 to 47 knots. On the Beaufort scale that is force 8 to 9, gale to strong gale.
- Storm Warning: 48 to 63 knots.
- Hurricane Force Wind Warning: 64 knots or more, from a non-tropical storm such as a strong nor'easter. In Boat or Nope that headline is a No-Go on its own.
Each has a matching watch, meaning the risk has increased but timing or location is still uncertain. A Gale Watch for tomorrow is a reason to plan around it now, not to find out at the dock.
The Coast Pilot notes that from October through March, gales in the Nantucket Sound area can be expected about 3 to 6 percent of the time and frequently come from the west and northwest. That is worth remembering when you plan a late-season trip or a ride to the yard for haul-out. The Nantucket Sound forecast and the Cape Cod Bay forecast are the regional pages I open next to Buzzards Bay.
Special Marine Warning: the short-fuse one
Special Marine Warnings cover fast-moving, short-lived hazards, usually two hours or less: thunderstorm winds or gusts of 34 knots or more, large hail, waterspouts, or a squall line or sharp cold front producing those winds. They are issued for specific areas and often for a specific storm. The Coast Pilot notes that local squall lines can bring winds gusting to 60 knots.
If one is issued for where you are, head for the nearest safe harbor, get everyone in life jackets, and stay low. Do not try to outrun a storm across open water.
Hazardous seas and freezing spray
A Hazardous Seas Warning is about the waves, not the wind. It is issued when wave height or steepness crosses locally defined warning levels, sometimes on days when the wind itself is not remarkable. Heavy Freezing Spray is a winter warning for ice building up on a boat fast enough to affect its stability: 2 centimeters per hour or more, or 0.7 centimeters per hour in Alaska.
Long Island Sound has its own headline history. Start with the Long Island Sound marine forecast and then open the harbor you are actually leaving from.
How Boat or Nope uses these headlines
The official marine headline for your zone drives the call, before the wind and wave math. How the call is built is the longer version. The short version:
- Warnings mean No-Go. That covers a Gale, Storm, Hurricane Force Wind, Special Marine, Hazardous Seas, Heavy Freezing Spray, Severe Thunderstorm, Tropical Storm, or Hurricane Warning.
- Advisories and watches mean Caution at best. A Small Craft Advisory, Dense Fog Advisory, Brisk Wind Advisory, Marine Weather Statement, or a Gale, Storm, or tropical watch caps the call at Caution. If your own limits are exceeded, it is still No-Go.
- Your own limits still apply. Wind, gusts (default: your wind limit plus 5 knots), and seas are checked against your boat. Estimated seas never produce a Go.
- The reason is always one line, with the headline named: "Caution: Small Craft Advisory NW 20 kt gusting 30 at 9 AM."
Each regional marine forecast page links the harbors around that water. Buzzards Bay is the one I check most.
Quick rules of thumb
- Read the headline before the numbers. How to read a marine forecast is the order I use.
- Advisory means think hard. Warning means do not go.
- A watch tomorrow means plan today.
- Check when it ends. Advisories list their valid times, and conditions often ease after a front passes.
- Re-check on the water. Special Marine Warnings can be issued with little lead time, so keep a VHF radio tuned to NOAA Weather Radio.