What Is a Blizzard and What Is a Blizzard Warning?

People walking in blizzard conditions

Blizzard Warnings aren’t all that common, but when they are issued, you know that a snowstorm means business. The National Weather Service only issues Blizzard Warnings when they are confident that weather conditions in a given area will meet the criteria for a blizzard either right now or in the imminent future. You’ll learn more about the requirements for a blizzard later in this article.

Blizzards, and thus blizzard warnings, are most common in the Northern Plains of the US, extending from eastern Montana to Minnesota and down to Colorado. However, blizzards can occur almost anywhere in the US outside the Deep South and the western Desert Southwest.

In this article, you’ll learn what criteria need to be met for a blizzard to occur officially. You’ll also learn about some of the dangers blizzards may pose to you and how to avoid or mitigate them. Finally, you’ll discover the difference between Blizzard Warnings and other similar National Weather Service alerts such as Winter Storm Watches and Ice Storm Warnings.

What Is a Blizzard?

Snow plow removing snow from a road

The term blizzard defines a severe snowstorm with strong, damaging winds and low visibility. It’s not just any old snowstorm! For a given location to technically experience a blizzard, the snowstorm must meet three criteria:

  • Winds must be sustained or frequently gusting above 35mph
  • Low visibility of 1/4 mile or less due to falling and/or blowing snow
  • These conditions must be present for at least three consecutive hours.

These criteria are selected to differentiate between regular snowstorms (whose primary impact is the accumulation of new snow) and blizzards (whose primary impact is severely reduced visibility).

In fact, you can have a blizzard without a single cloud in the sky! All you need is snow already on the ground and strong winds to blow it around so much that visibility is impaired. These blizzards that occur without snow falling from clouds in the sky are known as ground blizzards because the relevant snow gets lifted from the ground.

Trucks driving in a blizzard

Blizzards are especially dangerous for those traveling. Strong winds can make handling a car difficult on dry pavement, but during a blizzard, the road is covered by snow and ice, sometimes to a depth of several feet. Furthermore, the snow-covered edges of the road can be challenging to discern, thanks to extremely low visibility. Reflective markers have been added to the edges of many highways to help with this, but they’re usually spaced several hundred feet apart, and during some blizzards, you can’t even see that far!

Weather Conditions Required for a Blizzard to Form

Like any weather phenomenon, specific conditions need to exist for blizzards to form:

1. A strong pressure gradient to produce wind

Wind is an essential ingredient for blizzards, and it occurs when there is a change in barometric pressure over some distance. This change in pressure over distance is known as a pressure gradient. A strong pressure gradient occurs when a strong area of high pressure is located near a strong area of low pressure. Wind is produced by this pressure gradient, and its intensity is directly proportional to the strength of the gradient, so a stronger gradient will support stronger winds.

2. A source of snow, either already on the ground or from a storm system

Snow is the other key ingredient without which you can’t have a blizzard. Snow can be provided either by the same storm system bringing the wind or by a pre-existing snowpack. If there isn’t already snow on the ground, you need moisture and rising motion to produce new snow. Sometimes the rising motion can happen when air is forced to rise over a mountain range, or it could happen when warm and moisture-rich air is forced to rise over a slab of cold air.

3. Enough cold air for snow

You also need enough cold air either for new precipitation to fall as snow or for the pre-existing snow not to melt. If new snow is falling, it can’t be the sticky kind that’s good for snowballs. The lighter, fluffier snow will be more effective at blowing around and achieving the visibility reduction needed for a blizzard.

What Is a Blizzard Warning?

Blizzard warning event count by WFO
Blizzard Warnings issued from January 1st, 2010 – July 5th, 2022, by Weather Forecast Offices (WFO) of the National Weather Service (NWS) (Image Credit: Iowa Environmental Mesonet)

The National Weather Services will issue a Blizzard Warning when blizzard conditions are occurring or are imminent. Low visibility of 1/4 mile or less due to heavy falling and/or blowing snow in addition to winds of at least 35 mph are expected for at least 3 hours.

Blizzard Warnings are usually issued between 12 and 24 hours before the blizzard is forecast to arrive. The warnings help you stay safe by alerting you about the storm’s unique dangers that extend beyond what you might see in a more garden-variety winter storm.

Blizzard Warning vs. Other Winter Weather Alerts

To help the public prepare for severe winter weather, the National Weather Service issues a number of different alerts depending on the situation. Winter Storm Watches are issued when severe winter weather may occur in the near future but are not yet imminent (usually at least 24 hours before). If a watch is issued for your area, begin preliminary preparations for winter weather. You should refresh your food supplies and adjust travel plans if possible so that you don’t need to be on the road when bad weather hits.

Blizzard Watches were once issued when forecasters thought a blizzard might occur. However, in 2018 the National Weather Service updated its policy to only issue Winter Storm Watches to simplify the watch/warning system.

As a storm gets closer and forecast confidence increases, the watch may be upgraded to either a Winter Storm Warning, a Blizzard Warning, or an Ice Storm Warning, depending on what aspects of the storm might be most dangerous. This upgrade usually happens between 12 and 24 hours before a storm begins.

Ice Storm Warnings are only issued if specific criteria are met regarding how much ice is expected to accumulate on trees and power lines due to freezing rain. These criteria vary by location but are generally chosen to signify high odds of significant tree damage and extended power outages.

Suppose a winter storm isn’t expected to meet either blizzard or ice storm criteria but will still pose a major threat, especially to travel. In that case, a Winter Storm Warning will be issued. As a result, Winter Storm Warnings are fairly common across the northern US, while Blizzard Warnings and Ice Storm Warnings are considerably rarer.

Blizzard Safety Tips

Cars in Blizzard Conditions

Blizzards can be dangerous, but that doesn’t mean you need to feel their full wrath. Following these safety tips can turn a blizzard from a potentially deadly menace into a manageable inconvenience.

  • Stay indoors. Blizzards can be extremely dangerous if you’re outside. The strong wind, blowing snow, and cold temperatures can produce frostbite and hypothermia quickly. Reduced visibility may make it difficult to return to safety once outside. The best way to avoid these problems is to remain indoors!
  • Have an alternate source of indoor heat and light. Your power and heat may go out due to a blizzard’s strong winds. Plan to keep warm by securing an alternate source of heat. Such as a well-ventilated fireplace or a backup generator placed outside. You’ll also need a backup light source to illuminate dark indoor spaces, especially at night. Flashlights are your best bet for this, as candles pose a significant fire hazard. Make sure you have flashlights and extra batteries on hand before a blizzard strikes.
  • Only drive in an absolute emergency. The most dangerous place to be in a blizzard is on the road. Make sure you have all your necessary supplies before the blizzard hits so you can safely remain in place until it passes. Should an emergency arise and force you to drive, pack extra food, water, and clothing in case you get stuck. Also, pack a shovel and material to give you extra traction (sand, non-clumping cat litter, ice melt). If you get stuck in your car, stay in your vehicle until help arrives.
  • Stay up-to-date with the latest weather information. Blizzards, by definition, are long-lasting events (at least three hours). Make sure you have a way to get the latest weather information in case of forecast changes during the storm. An NOAA weather radio is your best option because it will work even if your power and internet go down, but a mobile device and TV can also work. Read our buying guide to find a reliable weather radio for your home.
  • Avoid carbon monoxide poisoning. Carbon monoxide is a toxic, odorless gas produced by combustion and is one of the leading causes of death during and after blizzards. Prevent carbon monoxide poisoning by ensuring your fireplace and furnace exhaust valves are free of snow and by never running a backup generator indoors.
  • Make sure you have plenty of supplies. The last thing you want to do in a blizzard is to have to go for a last-minute shopping trip. Make sure you have enough supplies to last for the duration of the storm and some time after. Remember, it takes time for the snow to be cleared from roads and for travel conditions to return to normal. Stocking up on food essentials (preferably non-perishable) and any necessary medication before a blizzard arrives is the best course of action.

Now that you know what a Blizzard Warning is and how to keep yourself safe if a blizzard strikes your area, tell a friend so they can be prepared too!

Published: July 21, 2022

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