Coastal Waters Forecast or Nearshore Marine Forecast products. Thresholds necessitating the issuance of small craft advisories are determined by the accordant NWS Regional Headquarters. Small craft advisory for hazardous seas (SCAH) – An advisory to mariners of wave or sea conditions that are potentially hazardous to small boats because of wave height, wave period, steepness, or swell direction, even if wind speeds are expected to fall below locally defined small craft advisory criteria. Only issued by WFOs in coastal regions and the Great Lakes for areas included in the Coastal Waters Forecast or Nearshore Marine Forecast products. Thresholds necessitating the issuance of this type of small craft advisory vary among geographic areas within each NWS Regional Headquarters. Small craft advisory for rough bar (SCARB) – Waves in or near harbor or river entrances are expected to be especially hazardous to mariners due to the interaction of swell, tidal and/or river currents in relatively shallow water. Thresholds governing the issuance of this type of small craft advisory vary among local geographic areas, and are based upon locally determined parameters such as wave steepness, wind speed and direction, and local bathymetry. Small craft advisory for winds (SCAW) – Wind speeds may pose potential hazards for maritime activity. Wave heights must remain below standard small craft advisory criteria to merit the issuance of a wind-based advisory. Thresholds necessitating the issuance of wind-based small craft advisories are determined by the accordant NWS Regional Headquarters. Brisk wind advisory (NPW) – Sea or lake ice is expected and may be hazardous to small marine craft. May be issued as a Small Craft Advisory with reference of being a brisk wind advisory. This advisory is not issued by WFOs serving the Great Lakes region due to the prevalence of ice floes during winter in the lake bodies. Temperature See also Windchill section below. Excessive heat warning (NPW) – Maximum Heat Index (HI) values are forecast to meet or exceed locally defined warning criteria for more than three hours over at least two consecutive days. Excessive Heat Warning are issued within 12 hours of the onset of the following Heat Index (HI) values criteria. Specific criteria vary among local Weather Forecast Offices, due to climate variability and the effect of excessive heat on the local population. Typical HI values are maximum daytime temperatures above for up to three hours per day, with minimum nighttime temperatures above (criteria may