These terms highlight important information about expected conditions in the region they are issued for. These warnings and advisories can be issued for temperatures, snowfall, and freezing rain and sleet. They also can warn of dangerous wind chill conditions, which can be equally as life threatening.
Winter Weather Warnings for Temperature and Wind Chill
Warnings for temperature specifically are only issued in Canada. Environment Canada (EC) issues a Cold Wave Warning when temperatures are expected to fall sharply in the matter of only a few hours. Related to this is the Flash Freeze Warning, which alerts the public to conditions which could be conducive to the freezing of wet or snow covered roadways.
Both the EC and the National Weather Service (NWS) both issue Wind Chill Warnings. This advisory warns to the expectation of cold temperatures and wind, which combine to make the temperature feel well below zero. The levels needed vary from region to region, but are generally for temperatures well below zero. In the US, the NWS may issue a Wind Chill Advisory for wind chill temperatures that fall closer to zero Fahrenheit.
Warnings for Snowfall and Blizzard Conditions
Many weather warnings deal with snow. In the US, the most basic winter advisory is the Winter Weather Advisory. This warning is issued for winter weather that while inconveniencing, they should not be hazardous or life-threatening when proper precautions are taken.
In Canada, there is not really a basic warning for snow. EC issues a Snowfall Warning when snow of anywhere from 5cm in Southwestern British Columbia up to as much as 20 or 25cm elsewhere is expected to fall over the next 12 to 24 hours.
Both countries' weather bureaus issue Winter Storm Watches and Winter Storm Warnings for the combination of hazardous and potentially life-threatening winter precipitation, strong winds, and wind chills. In the US a Watch is typically issued 24 to 36 hours in advance, and a Warning about 12 to 24 hours ahead of time; in Canada it is up to 48 hours ahead of time and 12 to 14 hours respectively.
Blizzard Warnings in both countries are reserved for the most life-threatening and strongest storms. The criteria for these storms do vary, but overall expect very strong winds, extremely cold temperatures, low wind chill, and heavy snow.
Warnings for Freezing Rain and Icing Events
Ice storms also have their own set of advisories. For minor events where only a small amount of ice is expected to accrue, the NWS will issue a Freezing Rain or Freezing Drizzle Advisory. An Ice Storm Warning is issued typically for icing events of 1/4" or more, although it does vary from region to region. In Canada, the equivalents to the NWS advisories are the Freezing Rain Warning and Freezing Drizzle Warning.
For more information:
- US Weather Warning Descriptions
- Canadian Weather Warning Descriptions
