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Definition
Is it a blizzard?
Heavy snow is not the test. The National Weather Service asks about the wind, the view, and how long both last.
The National Weather Service glossary says a blizzard means that the following conditions are expected to prevail for a period of 3 hours or longer. [NWS GLOSSARY] Those conditions include sustained wind or frequent gusts to 35 miles an hour or greater. [NWS GLOSSARY] They also include considerable falling and/or blowing snow, reducing visibility frequently to less than ¼ mile. [NWS GLOSSARY]
A Blizzard Warning, the glossary says, is issued for winter storms with sustained or frequent winds of 35 mph or higher, with considerable falling and/or blowing snow that frequently reduces visibility to ¼ of a mile or less, expected to prevail for a minimum of 3 hours. [NWS GLOSSARY] A Ground Blizzard Warning is issued when blizzard conditions are solely caused by blowing and drifting snow. [NWS GLOSSARY]
Tick the conditions that are happening, or that a forecast says will happen. The official wording stays in the table below, so the desk is a clearer view of the record, not a different one.
The National Weather Service definition needs all three: the wind, the poor visibility in falling or blowing snow, and a spell of at least three hours. Heavy snow on its own is not enough.
| Part | What the glossary says |
|---|---|
| Duration | The conditions are expected to prevail for a period of 3 hours or longer. |
| Wind | Sustained wind or frequent gusts to 35 miles an hour or greater. |
| Snow and view | Considerable falling and/or blowing snow (reducing visibility frequently to less than ¼ mile). |
| Ground blizzard | A Ground Blizzard Warning is issued when blizzard conditions are solely caused by blowing and drifting snow. |
The National Weather Service office in Flagstaff notes that while heavy snowfalls and severe cold often accompany blizzards, they are not required. [NWS FLAGSTAFF] Sometimes, that office says, strong winds pick up snow that has already fallen, creating a ground blizzard. [NWS FLAGSTAFF]
Warning names are not interchangeable
On its winter warnings page, the National Weather Service says a Blizzard Warning means falling and blowing snow with strong winds and poor visibilities are likely, leading to whiteout conditions making travel extremely difficult. [NWS WARNINGS] Its advice is: do not travel. If you must travel, have a winter survival kit with you. If you get stranded, stay with your vehicle and wait for help to arrive. [NWS WARNINGS] A Winter Storm Warning, by contrast, is issued for a significant winter weather event including snow, ice, sleet or blowing snow, or a combination of these hazards — travel may become difficult or impossible, and the Service says to delay travel plans until conditions improve. [NWS WARNINGS]
The safety page quotes the Service’s public advice for people caught in a winter storm, indoors or in a vehicle.