National Weather Service United States Department of Commerce

Definitions of Hazardous Weather
as used in the
Hazardous Weather Outlook (HWO)

The Hazardous Weather Outlook, issued at least once per day by the Weather Forecast Office in Birmingham, AL, is intended to provide plain language information on weather phenomena that are considered hazards. The threshold is the potential for a particular weather phenomena to require an outlook, watch, warning, or advisory from the National Weather Service.

Convective Weather - Thunderstorms capable of producing one inch or larger hail, damaging winds (wind speeds 58 mph or higher), and tornadoes will be discussed in the HWO. When conditions are favorable for localized microbursts (pulse summertime storms), information regarding this type of thunderstorm will also be included.

Winter Weather - Snow, freezing rain, sleet, or a mixture of these weather phenomena that may lead to a winter weather outlook, winter storm watch, winter storm warning, or winter weather advisory, will be included.

Non Precipitation - Weather hazards such as strong winds, excessive heat or cold, and dense fog will be included in the HWO.

Fire Weather - Extremely dry and windy conditions that result in high fire danger situations will be included.

Flooding - Flood hazards such as minor flooding, flash flooding, and long duration river flooding will be in the HWO.

Non-hazardous Weather - Non-hazardous weather phenomena will not routinely be discussed in the HWO. These weather phenomena do not require the issuance of an outlook, watch, warning, or advisory. Examples include widespread rain where flooding is not expected, general thunderstorms, showers, 20 mph winds, fog where visibilities are 1 mile or greater, light snow resulting in little or no accumulation, etc.