CAT Model

An air quality alert is issued when there are elevated levels of ozone or pollutants are expected to be in the unhealthy range for sensitive groups.

A Beach Hazards Statement is issued on days when a significant number of boats and paddle craft are expected to be out on the water and when warm air temperatures may cause people to underestimate the danger of the cold water.

A Blizzard Warning means that the following conditions are occurring or expected within the next 12 to 18 hours.

1. Snow and/or blowing snow reducing visibility to 1/4 mile or less for 3 hours or longer and,

2. Sustained winds of 35 mph or greater or frequent gusts to 35 mph or greater.

There is no temperature requirement that must be met to achieve blizzard conditions.

A Coastal Flood Advisory is issued when minor or nuisance coastal flooding is occurring or imminent.

A Coastal Flood Warning is issued when moderate to major coastal flooding is occurring or imminent. This flooding will pose a serious risk to life and property.

A Coastal Flood Watch is issued when moderate to major coastal flooding is possible. Such flooding would potentially pose a serious risk to life and property.

A Dense Fog Advisory is issued when widespread fog is expected to reduce visibilities to 1/4 mile or less over a large area for an extended period of time (2 or more hours).

An Excessive Heat Warning is issued when the heat index value is expected to reach or exceed 105 degrees within the next 12 to 24 hours. An Excessive Heat Warning may be issued for lower criteria if it is early in the season or during a multi-day heat wave.

An Excessive Heat Watch is issued when there is a potential for the heat index value to reach or exceed 105 degrees within the next 24 to 48 hours.

An Extreme Wind Warning is issued for surface winds of 100 knots (115 MPH) or greater associated with non-convective, downslope, derecho (NOT associated with a tornado), or sustained hurricane winds are expected to occur within one hour.

A Fire Weather Watch is issued to alert fire officials and firefighters of potentially dangerous fire weather conditions within the next 24 to 36 hours. They are issued when the following three criteria are met:

1. Surface relative humidity (RH) less than 30 %

2. Sustained surface wind of 20 MPH or greater

3. 10-hour fuel moisture less than 8%

A Flash Flood Warning is issued when flash flooding is imminent or occurring.

A Flood Warning is issued when flooding is imminent or occurring.

A Flood Watch is issued when conditions are favorable for flooding. It does not mean flooding will occur, but it is possible.

A Freeze Warning is issued when significant, widespread freezing temperatures are expected.

A Freeze Warning is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). A Freeze Warning is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops).

A Freeze Watch is issued when there is a potential for significant, widespread freezing temperatures within the next 24-36 hours.

A Freeze Watch is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). A Freeze Watch is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops).

A Frost Advisory is issued when the minimum temperature is forecast to be 33 to 36 degrees on clear and calm nights during the growing season.

A Frost Advisory is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). A Frost Advisory is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops).

Gale Warnings are issued for the coastal areas when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:

1. sustained winds of 34 knots to 47 knots

2. frequent gusts (duration of two or more hours) between 34 knots and 47 knots.

A Hazardous Seas Watch is issued by the National Weather Service of the United States when there is an increased threat of high wave heights and/or wave steepness values reach a certain criteria, but the occurrence, timing, and/or location are still uncertain, though the area of concern is known.

The Hazardous Weather Outlook will describe potential hazardous weather and hydrologic information of concern in Days 1 through 7. The outlook contains two segments: One segment for the marine zones and adjacent land-based (i.e., coastal) zones and the other segment for the rest of the land-based zones. Each segment of the HWO will contain 3 sections: short term through Day 1, long term for Days 2-7, and spotter information.

A Heat Advisory is issued when the heat index value is expected to reach 100 to 104 degrees within the next 12 to 24 hours. A Heat Advisory may be issued for lower criteria if it is early in the season or during a multi-day heat wave.

A High Wind Warning is issued when the following conditions are expected:

1. sustained winds of 40 mph or higher for one hour or more, or

2. wind gusts of 58 mph or higher for any duration.

Hurricane Force Wind Warnings are issued when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:

1. sustained winds of 64 knots or greater

2. frequent gusts (duration of two or more hours) of 64 knots or greater

A Hurricane Warning is issued when sustained winds of 64 kt (74 mph) or higher associated with a tropical cyclone are expected in 36 hours or less. These winds may be accompanied by storm surge, coastal flooding, and/or river flooding. A hurricane warning can remain in effect when dangerously high water or a combination of dangerously high water and exceptionally high waves continue, even though winds may be less than hurricane force.

A Hurricane Watch is issued when a tropical cyclone containing winds of 64 kt (74 mph) or higher poses a possible threat, generally within 48 hours. These winds may be accompanied by storm surge, coastal flooding, and/or river flooding.

The watch does not mean that hurricane conditions will occur. It only means that these conditions are possible.

Hydrologic Outlooks are issued to provide information on hydro-meteorological conditions which could cause flooding in the near term, generally within 1-7 days.

¼ inch or more of ice accumulation.

A lake wind advisory is issued by the United States National Weather Service local forecast offices when windy conditions on area lakes are expected to be hazardous for boaters and other recreational events on or around lakes.

A Red Flag Warning is issued to alert fire officials and firefighters of potentially dangerous fire weather conditions within the next 12 to 24 hours. They are issued when the following three criteria are met:

1. Surface relative humidity (RH) less than 30 %

2. Sustained surface wind of 20 MPH or greater

3. 10-hour fuel moisture less than 8%

A rip current statement is a warning statement issued when there is a high threat of rip currents due to weather and ocean conditions.

A River Flood Warning is issued when river flooding is occurring or imminent at one or more forecast points along a river.

A Severe Thunderstorm Warning is issued when severe thunderstorms are occurring or imminent in the warning area. Severe thunderstorms are defined as follows:

1. Winds of 58 mph or higher, and/or

2. Hail 1 inch in diameter or larger.

A Severe Thunderstorm Watch is issued when severe thunderstorms are possible in and near the watch area. It does not mean that they will occur. It only means they are possible. Severe thunderstorms are defined as follows:

1. Winds of 58 mph or higher, and/or

2. Hail 1 inch in diameter or larger.

Small Craft Advisories are issued when one or more of the following conditions is expected to begin within 36 hours:

1. sustained winds of 18 knots to 33 knots

2. frequent gusts (duration of two or more hours) between 18 knots and 33 knots.

3. waves of 4 feet or higher

A warning of potentially hazardous weather conditions of short duration (up to 2 hours) affecting areas that are not adequately covered by existing marine warnings and producing one or more of the following:

1. Sustained marine convective winds (showers/thunderstorms) or associated gusts of 34 knots or greater

2. Hail three quarters of an inch or more in diameter

3. Waterspouts

Storm Warnings are issued when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:

1. sustained winds of 48 knots to 63 knots

2. frequent gusts (duration of two or more hours) of 48 knots to 63 knots

A Tornado Warning is issued when a tornado is imminent. When a tornado warning is issued, seek safe shelter immediately.

A Tornado Watch is issued when severe thunderstorms and tornadoes are possible in and near the watch area. It does not mean that they will occur. It only means they are possible. Severe thunderstorms are defined as follows:

1. Winds of 58 mph or higher, and/or

2. Hail 1 inch in diameter or larger

A Tropical Storm Warning is issued when sustained winds of 34 to 63 kt (39 to 73 mph) or higher associated with a tropical cyclone are expected in 36 hours or less. These winds may be accompanied by storm surge, coastal flooding, and/or river flooding.

A Tropical Storm Watch is issued when a tropical cyclone containing winds of 34 to 63 kt (39 to 73 mph) or higher poses a possible threat, generally within 48 hours. These winds may be accompanied by storm surge, coastal flooding, and/or river flooding.

The watch does not mean that tropical storm conditions will occur. It only means that these conditions are possible.

A Wind Advisory is issued when one or both of the following conditions are expected:

1. sustained winds of 31 to 39 mph for an hour or more.

2. wind gusts of 46 to 57 mph for any duration.

A Wind Chill Advisory is issued when wind chills of -5F to -19F are expected.

A Wind Chill Warning is issued when wind chills of -20F or lower are expected.

A Winter Storm Warning is issued when a significant combination of hazardous winter weather is occurring or imminent. Significant and hazardous winter weather is defined as a combination of one or more of the following:

1. 5 inches or more of snow/sleet within a 12-hour period or 7 inches or more of snow/sleet within a 24-hour period

2. Enough ice accumulation to cause damage to trees or powerlines.

3. A life threatening or damaging combination of snow and/or ice accumulation with wind.

Winter Storm Watch is issued when there is the potential for significant and hazardous winter weather within 48 hours. It does not mean that significant and hazardous winter weather will occur, only that it is possible. Significant and hazardous winter weather is defined as a combination of one or more of the following:

1. 5 inches or more of snow/sleet within a 12-hour period or 7 inches or more of snow/sleet within a 24-hour period

2. Enough ice accumulation to cause damage to trees or powerlines.

3. A life threatening or damaging combination of snow and/or ice accumulation with wind.

A Winter Weather Advisory will be issued for any amount of freezing rain, or when 2 to 4 inches of snow (alone or in combination with sleet and freezing rain), is expected to cause a significant inconvenience, but not serious enough to warrant a warning.

If the event is expected to impact metro areas during rush hours (4-9 am or 2-7 pm on weekdays) forecasted snow totals of one inch will necessitate the issuance of a winter weather advisory.