What do they all mean?

When severe weather of any kind is possible, you’re likely to see the watches and warnings issued by the National Weather Service, telling you that dangerous weather could be on the way.

When you see those alerts — which you’re likely to get through notifications on your phone or scrolling across your TV screen — you may have questions.

What’s the difference between an “outlook“, an “advisory” or most importantly the difference between a “watch and a “warning“? And what do the terms actually mean for specific weather events?

Using graphs, methodology and information provided by the National Weather Service (NWS) among others, we hope to provide useful and important information on these weather alerts.

Scroll below for watch & warning criteria for many of the weather event we experience here in the Lehigh Valley. 

For more alerts and information visit Weather Criteria

 

A Fire Weather Watch or Red Flag Warning is issued when the combination of dry fuels and weather conditions support extreme fire danger. These products are written for land and fire managers to highlight the increased fire danger.

Each National Weather Service (NWS) office creates local criteria for fire weather watches and red flag warnings.

    • Red Flag Warnings are usually only issued during the spring and fall fire weather seasons, February 15th through April 30th and October 1st through December 15th. When warnings are issued, officials know to curtail planned or controlled burns and to be on the lookout for wildfires.
    • A Fire Weather Watch are alerts for officials and land management agencies to advise them of the high potential for development of Red Flag Warning criteria in the next 12 – 72 hours. The watch may be issued for all, or portions of a fire weather zone or region. Zones impacted by the event will be listed within the Red Flag Warning.

    • Severe Thunderstorm Warning – Take Action! Severe weather has been reported by spotters or indicated by radar. Warnings indicate imminent danger to life and property. Take shelter in a substantial building. Get out of mobile homes that can blow over in high winds. Warnings typically encompass a much smaller area (around the size of a city or small county) that may be impacted by a large hail or damaging wind identified by an NWS forecaster on radar or by a trained spotter / law enforcement who is watching the storm.
    • Severe Thunderstorm Watch – Be Prepared! Severe thunderstorms are possible in and near the watch area. Stay informed and be ready to act if a severe thunderstorm warning is issued. The watch area is typically large, covering numerous counties or even states.

 

 

 

 

 

 

    • Flash Flood Warning – Take Action! A Flash Flood Warning is issued when a flash flood is imminent or occurring. If you are in a flood prone area move immediately to high ground. A flash flood is a sudden violent flood that can take from minutes to hours to develop. It is even possible to experience a flash flood in areas not immediately receiving rain. Flash Flood Warnings are changing to an Impact-Based format to improve public response. Read the factsheet.
    • Flood Warning – Take Action! A Flood Warning is issued when the hazardous weather event is imminent or already happening.
    • Flood Advisory – Be Aware! A Flood Advisory is issued when a specific weather event that is forecast to occur may become a nuisance. A Flood Advisory is issued when flooding is not expected to be bad enough to issue a warning. However, it may cause significant inconvenience, and if caution is not exercised, it could lead to situations that may threaten life and/or property.
    • Flood Watch – Be Prepared! A Flood Watch is issued when conditions are favorable for flooding. It does not mean flooding will occur, but it is possible.

 

 

 

 

 

 

 

    • Excessive Heat Warning – Take Action! An Excessive Heat Warning is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this Warning is when the maximum heat index temperature is expected to be 105° or higher for at least 2 days and night time air temperatures will not drop below 75°; however, these criteria vary across the country, especially for areas not used to extreme heat conditions. If you don’t take precautions immediately when conditions are extreme, you may become seriously ill or even die.
    • Excessive Heat Watches – Be Prepared! Heat watches are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A Watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain.
    • Heat Advisory – Take Action! A Heat Advisory is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this Advisory is when the maximum heat index temperature is expected to be 100° or higher for at least 2 days, and night time air temperatures will not drop below 75°; however, these criteria vary across the country, especially for areas that are not used to dangerous heat conditions. Take precautions to avoid heat illness. If you don’t take precautions, you may become seriously ill or even die.
    • Excessive Heat Outlooks – Be Aware! The outlooks are issued when the potential exists for an excessive heat event in the next 3 – 7 days. An Outlook provides information to those who need considerable lead-time to prepare for the event.

    • Tornado Warning – Take Action! A tornado has been sighted or indicated by weather radar. Avoid windows! If in a mobile home, a vehicle, or outdoors, move to the closest substantial shelter and protect yourself from flying debris. Warnings are issued by your local forecast office. Warnings typically encompass a much smaller area (around the size of a city or small county) that may be impacted by a tornado identified by a forecaster on radar or by a trained spotter / law enforcement who is watching the storm.
    • Tornado Watch – Be Prepared! A Tornadoes are possible in and near the watch area. Review and discuss your emergency plans and check supplies and your safe room. Be ready to act quickly if a warming is issued or you suspect a tornado is approaching. Acting early helps to save lives! Watches are issued by the Storm Prediction Center for counties where tornadoes may occur. The watch area is typically large, covering numerous counties or even states.

 

 

 

 

 

 

 

Winter Weather Advisory

    • 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.

Winter Storm Watch

    • A 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 will occur.. it only means it is possible! Significant and hazardous winter weather is defined as a combination of:
      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 AND/OR
      2. Enough ice accumulation to cause damage to trees or powerlines AND/OR
      3. a life threatening or damaging combination of snow and/or ice accumulation with wind.

Winter Storm Warning

    • 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:
      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 AND/OR
      2. Enough ice accumulation to cause damage to trees or powerlines AND/OR
      3. a life threatening or damaging combination of snow and/or ice accumulation with wind.

Blizzard Warning

    • A Blizzard Warning means that the following conditions are occurring or expected within the next 12 to 18 hours. (There is no temperature requirement that must be met to achieve blizzard conditions).
      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.

Ice Storm Warning

    • An Ice Storm Warning means there is an expected accumulation of ice of 1/4 inch or more. Travel will or may become nearly impossible and expect downed trees / power lines and power outages.

Freeze Warning

    • 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 occurence of first widespread freeze). The normal end of the growing season is mid to late October west of the Blue Ridge and early November east of the Blue Ridge. However, during anomalously warm autumns, the growing season may be extended past the normal end of the growing season.
    • 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).

Frost Advisory

    • A Frost Advisory is issued when the minimum temperature is forecast to be 33 to 36 degrees on clear and calm nights during growing season.
    • A Frost Advisory is issued in the autumn until the end of the growing season (marked by the occurence of first widespread freeze). The normal end of the growing season is mid to late October west of the Blue Ridge and early November east of the Blue Ridge. However, during anomalously warm autumns, the growing season may be extended past the normal end of the growing season.
    • 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).