WWA Criteria

Outlook – Issued to indicate that a hazardous weather event may develop. It is intended to provide information to those who need considerable lead time to prepare for the event. May be issued days in advance.

Watch – Issued when the risk of a hazardous weather event has increased, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. Depending on the type of watch/hazard may be issued hours to a few days in advance.

Warning/Advisory – These products are issued when a hazardous weather event is occurring, is imminent, or has a very high probability of occurrence. A warning is used for conditions posing a threat to life or property. An advisory is for less serious conditions that cause significant inconvenience and, if caution is not exercised, could lead to situations that may threaten life and/or property.

Statement – These products are issued when hazardous weather is occurring or is imminent, but are sub-warning or advisory levels.

Tropical Cyclone Products
Tropical Storm	Watch	Tropical storm force winds possible; issued 48 hrs prior to arrival of tropical storm force winds.
Tropical Storm	Warning	Tropical storm force winds expected; issued 36 hrs prior to arrival of tropical storm force winds.
Hurricane	Watch	Hurricane conditions possible; issued 48 hrs prior to the arrival of tropical storm force winds.
Hurricane	Warning	Hurricane conditions expected; issued 36 hrs prior to the arrival of tropical storm force winds.
Storm Surge	Watch	Life-threatening surge possible; issued 48 hours prior to the arrival of surge flooding impacts.
Storm Surge	Warning	Life-threatening surge expected; issued 36 hours prior to the arrival of surge flooding impacts.
Extreme Wind	Warning	Sustained winds of 115 mph or greater (Cat 3) are expected within an hour (major hurricane eyewall landfall).

Thunderstorm Products
Severe Thunderstorm	Watch	Severe thunderstorms, containing large hail and/or damaging winds, are possible.
Severe Thunderstorm	Warning	Severe thunderstorms with large hail (>= 1 inch in diameter) and/or damaging winds (>=58 mph gusts) are imminent or occurring.
Tornado	Watch	Tornadoes are possible, conditions favorable.
	Warning	Tornadoes are imminent or occurring; take shelter. Tornado warnings are usually base, but issue considerable or catastrophic for higher-end tornadoes.
	Emergency	Exceedingly rare, only used when: severe threat to human life is imminent or ongoing, catastrophic damage is imminent or occurring, have visual or radar evidence of a damaging tornado.
Significant Weather	Statement	Issued for strong, not quite severe thunderstorms (e.g. < 1-inch diameter hail, 40+ mph winds, frequent lightning, funnel clouds).

Flood Products
Flood	Watch	Potential (50 to 80%) for life-threatening flooding/flash flooding in the next 48 hours; can be due to rainfall or the possibility of dam failure.
	Warning	Flash Flood: Life threatening flooding imminent or occurring, from heavy rainfall or dam failure. Depending on the severity of impacts, the following threat tags may be used: base, considerable.
	Warning	Areal Flood: Develops more gradually, usually from prolonged and persistent moderate to heavy rainfall.
	Emergency	Exceedingly rare, violent flash floods which threaten lives and cause disastrous damage when floodwaters are placing or will place people in life-threatening situations by rapidly rising to levels rarely, if ever, seen.
	Advisory	Non-life-threatening flooding is expected. Typically used for minor flooding in areas of poor drainage, small streams, or urban areas.

Winter Weather Products
Winter Storm	Watch	*For Washington, Burleson, Brazos, Grimes, Madison, Walker, Houston, and Trinity counties:* Potential for 2+ inches of snow and/or ½ inch of sleet and/or 1/8 inch of ice accretion from freezing rain with sleet or snow. This can become a Warning or a Winter Weather Advisory. For the rest of the region: Potential for 1+ inches of snow and/or ½ inch of sleet and/or 1/8 inch of ice accretion from freezing rain with sleet or snow. This can become a Warning or a Winter Weather Advisory.
Winter Storm	Warning	*For Washington, Burleson, Brazos, Grimes, Madison, Walker, Houston, and Trinity counties:* 2+ inches of snow and/or ½ inch of sleet and/or 1/8 inch of ice accretion from freezing rain with sleet or snow is expected. For the rest of the region: 1+ inches of snow and/or ½ inch of sleet and/or 1/8 inch of ice accretion from freezing rain with sleet or snow. This can become a Warning or a Winter Weather Advisory. To view the entire country's criteria for Winter Storm Warnings for Heavy Snow visit this link.
Ice Storm	Warning	Greater than 1/8 an inch of ice accretion due to freezing rain; freezing rain is the predominant hazard. (Watches are not used for this product.)
Winter Weather	Advisory	*For Washington, Burleson, Brazos, Grimes, Madison, Walker, Houston, and Trinity counties:* Less than 2 inches of snow, less than ½ inch of sleet, less than 1/8 inch of ice or any combination is expected. For the rest of the region: Less than 1 inch of snow, less than ½ inch of sleet, less than 1/8 inch of ice, or any combination is expected.
Wind Chill	Watch	Wind chill index ≤ 0°F possible.
	Warning	Wind chill index ≤ 0°F expected.
	Advisory	Wind chill index ≤ 13°F, but > 0°F expected.
Freeze	Watch	Temperatures ≤ 32°F possible. (Only issued for the first freeze of the season, and possibly during the end of the winter if freezing temperatures are expected after a period of growing.)
Freeze	Warning	Temperatures ≤32°F expected. (Only issued for the first freeze of the season, and possibly during the end of the winter if freezing temperatures are expected after a period of growing.)
Hard Freeze	Watch	Temperatures ≤ 24°F possible for two hours or more.
Hard Freeze	Warning	Temperatures ≤ 24°F expected for two hours or more.

Marine Products
Small Craft	Caution	Sustained winds of 15 to 20 knots, and/or waves exceeding 4 feet.
Small Craft	Advisory	Sustained winds or frequent gusts greater than 20 knots, and/or waves greater than 7 feet.
Gale	Watch	Sustained winds or frequent gusts of 34 to 47 knots are possible.
Gale	Warning	Sustained winds or frequent gusts of 34 to 47 knots are expected.
Storm	Watch	Sustained winds or frequent gusts greater than 48 knots are possible.
Storm	Warning	Sustained winds or frequent gusts greater than 48 knots are expected.
Low Water	Advisory	Low water levels impacting marine traffic. Issued for forecast or observed water levels less than or equal to -1 ft MLLW.
Marine Dense Fog	Advisory	Sustained or frequent gusts of 34 knots or greater and/or hail of 3/4 inch or more in diameter, and/or waterspouts.
Special Marine	Warning	Temperatures ≤ 24°F expected for two hours or more.
Marine Weather	Statement	Provide detailed marine weather information describing non-severe, but potentially hazardous, conditions and information for a variety of conditions not covered by warnings or routine forecasts.

Coastal Products
Coastal Flood	Advisory	Tide levels with the potential for minor coastal flooding. Begin to consider this when tides exceed 3.5 feet above Mean Low Low Water (MLLW).
Coastal Flood	Warning	Tide levels with the potential for moderate or worse coastal flooding. In most locations, this is when tide levels exceed 4.5 to 5.0 feet above Mean Low Low Water (MLLW).
Rip Current	Statement	Issued when conditions favor the development of rip currents and/or reports of rip currents are received from Galveston Beach Patrol.
Beach Hazards	Statement	Issue when there are multiple coastal hazards at play (e.g. strong rip currents and higher than normal tide levels).

Fire Weather Products
Fire Weather	Watch	Favorable conditions are possible for fire starts and rapid fire spread (low relative humidity, dry fuels, high winds).
Red Flag	Warning	Favorable conditions expected for fire starts and rapid fire spread with Relative Humidity values 20-25% or less, Winds 15-20+ mph (sustained or frequent gusts), and dry grasses/fuels. Thresholds may be lowered if extremely dry fuels are occurring.

Non-Precipitation Products
Excessive Heat Click here for criteria across NWS Southern Region	Watch	Heat Index ≥ 113°F or Temperature ≥ 105°F possible. Threshold may be lowered during early season events or other special circumstances (e.g. power outages after tropical event).
	Warning	Heat Index ≥ 113°F or Temperature ≥ 105°F expected. Threshold may be lowered during early season events or other special circumstances (e.g. power outages after tropical event).
Heat	Advisory	Heat Index ≥ 108°F or Temperature ≥ 103°F possible. Threshold may be lowered during early season events or other special circumstances (e.g. power outages after tropical event).
High Wind	Watch	Sustained winds 40 mph or greater lasting one hour or longer and/or non-convective gusts 58 mph or greater is possible.
High Wind	Warning	Sustained winds 40 mph or greater lasting one hour or longer and/or non-convective gusts 58 mph or greater is expected.
Wind	Advisory	Sustained winds 25 mph or greater is expected.
Dust Storm	Warning	Widespread or localized blowing dust reducing visibilities to 1/4 mile or less.
Blowing Dust	Advisory	Widespread or localized blowing dust reducing visibilities to one mile or less, but greater than 1/4 mile.
Dense Fog	Advisory	Fog reducing visibility to less than 1/4 mile is expected.
Dense Smoke	Advisory	Smoke reducing visibility to less than 1/4 mile or less.

The above criteria are specific to the Houston/Galveston office. Other NWS offices may have different criteria for their products.