Let it snow, let it snow, let it snow… right?
Whether you hate it or love it, there’s no escaping it (unless you move somewhere too warm for it!) Students may love a good snow day, but any winter precipitation is a headache for your local department of transportation and commuters.
Snow is a common form of winter weather that you simply must prepare for. The best way to get ready for a snowstorm is to understand everything about this meteorological phenomenon. That’s where we come in.
This resource, compiled by our team of expert meteorologists, has everything you need to know about snow in it. If you’re ready to become a snow expert, you can start reading this free resource or use the buttons below to jump to a section that interests you most.
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If you want to understand this form of winter precipitation, it’s important you start with the basics. So what exactly is snow, and what is snow made of?
Snow is precipitation in the form of ice crystals. Because snow is comprised of ice, we can consider it a mineral.
Just for reference, a mineral is a naturally occurring homogeneous solid with a definite chemical composition and an ordered atomic arrangement that formed inorganically.
That’s our snow definition, but it doesn’t tell you everything you need to know.
How is Snow Formed?
The next thing you should know is how snow forms. This is a process that starts in the clouds.
The first ingredient is cold temperatures. It must be at or below the freezing point for snow to form. On the Celsius scale, that includes anything at 0 degrees or lower. For the Fahrenheit scale, the freezing point is 32 degrees.
When water vapor is in a warmer cloud, it enters into a liquid state. However, when temperatures are at the freezing point or below water vapor turns directly into ice.
Once an ice crystal forms in the clouds it absorbs and freezes additional water vapor from the surrounding air. As the crystal takes on more and more frozen water vapor, it forms into what we call a snow crystal or snow pellet. This pellet then falls to Earth where we see it float through the air and sometimes accumulate on the ground and other surfaces.
What Types of Snow are There?
According to the National Snow & Ice Data Center, there are four main types of snow crystals. They do not include sleet and hail.
What is sleet? Sleet is a precipitation form consisting of ice pellets, often falling with rain or snow. Sleet is actually very similar to hail. You can learn all about sleet and hail from our Weather 101 Hail Guide.
The four main types of snow crystals are:
Snowflakes are clusters of ice crystals that fall to the ground. They are probably the first type of precipitation you think of when you think of winter. Snowflakes can be light and airy or wet and heavy.
Hoarfrost is the deposition of ice crystals on a surface when the temperature of the surface is lower than the frost point of the surrounding air. Usually composed of interlocking ice crystals, hoarfrost forms on objects of small diameter that are freely exposed to air. This includes things like poles, tree branches, wires, plant stems, and leaf edges.
Graupel refers to snowflakes that become rounded, opaque pellets. These pellets range in size from a diameter of 0.1 to 0.2 inches. Graupel forms as ice crystals. They then fall through supercooled cloud droplets. Then these cloud droplets freeze to the crystals, forming a lumpy mass.
Don’t confuse graupel with hail; the two are different. Graupel normally has a texture that is softer and more crumbly. We also refer to graupel as snow pellets.
Polycrystals are snowflakes composed of many individual ice crystals.
What Types of Snowfall are There?
There are different snow types, but also different snowfall types. If you’ve ever driven in the white stuff, you can definitely tell the difference between a flurry and a blizzard.
Here are nine common snowfall types:
Lake Effect Snow
A blizzard is the worst of all snowfall types. Blizzards are violent winter storms that last at least three hours. These types of storms often have long-lasting implications because they include subfreezing temperatures, snowfall, and very strong winds. This combination leads to reduction in visibility and other dangerous conditions, like broken tree branches and dangerous cold.
The next type of snowfall is a typical snowstorm. A snowstorm is any snowfall with normal winds that produces large amounts of snowfall. Snowstorms are like more peaceful blizzards, although they can still produce dangerous amounts of snow.
A snow flurry is the next type of snowfall on our list. Flurries are snow that falls at very short durations. A flurry produces little to no accumulation, but can be intense at times.
A snow squall, or whiteout, is a brief but intense snowfall that greatly reduces visibility thanks to strong gusts of winds. Snow squalls are similar to blizzards, but differ in location, duration, and accumulation.
A snowburst is a very intense shower of snow. Often of short duration, snowbursts greatly restrict visibility and produce periods of rapid snow accumulation. During a snowburst, snow falls at a rate of 2 inches per hour or greater.
Blowing snow happens when wind picks up snow to a height of 8 feet or more. This type of snow reduces visibility. Blowing snow can happen with already-fallen or currently-falling snow.
Although they sound similar, drifting snow is different from blowing snow. Drifting snow is an ensemble of snow particles raised by the wind to small heights above the ground. It’s basically blowing snow that floats lower than 8 feet off the ground. The motion of the snow is more or less parallel to the ground.
Lake Effect Snow
The next type on our list is Lake Effect Snow. Lake effect snow is snow that falls on the lee side of a lake, generated by cold air passing over warmer water. This type of snow is especially common in the Great Lakes region, but can happen on smaller lakes.
While thundersnow isn’t a common term, it is a common event, and it’s probably a lot simpler than you think.
Thundersnow is a winter thunderstorm accompanied by snow. Some people also refer to this phenomenon as a thundersnowstorm or just a winter thunderstorm.
Thundersnow happens for one of three reasons. The first cause of thundersnow is a normal thunderstorm on the leading edge of a cold front that includes precipitation.
Another possible cause is a heavy synoptic snowstorm that sustains strong vertical mixing. The upward motion in these types of storms allows for favorable conditions for lightning and thunder to occur because warm air is trying to get through much cooler air.
The last reason why thundersnow happens is because of lake effect or ocean effect thunderstorms.
Snow Forecasts & Warnings
Now that you know basic snow facts, it’s time to learn about the tools available to help the public and organizations prepare. This section is all about forecasts and warnings available for snowstorms. Let’s get started!
Snow forecasts are important for ski resorts, departments of transportation, and schools. But forecasting snow is a complicated process that requires a lot of meteorological knowledge.
To forecast snow you need:
Knowledge of the numerical models so one can resolve which model has the best storm track
Understanding of whether the pattern the model is forecasting favors a major or minor snowstorm
An assessment of whether the model is handling the mesoscale structure correctly
Knowledge of the model low-level temperature biases
Figuring out the above information helps us accurately forecast if snow is coming, what type of precipitation it will be, and how intense the snowfall will be.
Earth Networks Sr. Meteorologist and Editor, James West, had this to say about forecasting snow:
“Snow forecasts are the hardest and most stressful forecasts to make for a meteorologist. There are many factors to consider when we make our forecast analysis. We have to worry about temperatures not only at the surface but also high up in the atmosphere. We need to know the position and strength of the winter storm and we even need to know local geography. Finally, we need to know how a snow forecast will affect our clients. Clients like Ski Resorts will love a big snow forecast while other clients have to prepare their staff for travel issues.”
Visualizing Snow Forecasts
Where do you find one of these forecasts? You can try searching the internet or your free weather application to see what the snow outlook is in your area. These tools will often provide the percent chance of snow and how many inches to expect.
You can also use commercial, subscription-based weather maps. Our weather mapping software specifically has three snow-related forecasts that users can see in real time. They are:
Snow Amount Forecast
Snow Probability Forecast
Freezing Rain Forecast
These forecasts add a bit more context to the incoming snow event to help businesses, schools, and government agencies prepare.
After reviewing your snow forecast, it’s important to receive alerts and warnings. Winter weather can be very dangerous, so warnings are key for preparing and staying safe as conditions change. The following are the most common, snow-related winter weather watches and warnings:
Winter Storm Warning (HIGH)
A winter storm warning means that snow, sleet, or ice is expected. At this point, you should take action. Confidence is high that a winter storm will produce dangerous conditions like heavy snow, sleet, or freezing rain. These conditions can cause significant damage.
Winter Storm Watch (MEDIUM)
A winter storm watch means that snow, sleet, or ice is possible. At this point, you should be prepared. A winter storm watch is a step below a winter storm warning. It means that confidence is medium that a winter storm could produce heavy snow, sleet, or freezing rain and cause significant impacts in your area.
Winter Weather Advisory (LOW)
A winter weather advisory is the least serious of all the NWS winter weather warnings. This simply means that winter weather is expected so you should exercise caution. Light amount of wintry precipitation or patchy blowing snow will cause slick conditions and could affect travel. Take precautions during a winter storm advisory and be prepared for things to intensify.
WHERE TO GET YOUR ALERTS
Snow alerts come in a variety of forms, be it text, email, online report, or application notification. The public can always look towards the National Weather Service’s winter weather warnings mentioned above. They’re a great starting point for business as well. But with winter weather like snowfall, certain businesses need more granular, detailed weather information from a tool like our Sferic Maps.
Forecasts & Warnings in Action
Safety before, during, and after a winter weather event is extremely important to responsible parties like government entities and employers. When people are relying on you to keep them safe, you can’t use free weather applications and warnings. That would be leaving too much up to chance.
What’s a better solution? It is to receive snow warnings and weather intelligence from a commercial weather provider (like us). Ideally, whatever commercial source of weather information you choose will have access to calibrated weather data from a neighborhood-level weather network and input from expert meteorologists (like we do).
Why are these things important? It all comes down to accuracy and timeliness, which help you take the appropriate action faster to save lives and protect property.
A PRACTICAL EXAMPLE: Montgomery County, Maryland
For example, the Montgomery County Department of Transportation (MCDOT) sets a great example with their use of a comprehensive winter weather safety policy with tools and advice from Earth Networks.
Maryland has its fair share of high-impact events during the winter months. For snow, state and local agencies have to plan ahead of time to secure enough plows and equipment to keep the roads clear. A lot is riding on an accurate, localized snow forecast. If the forecast is wrong, it can create prolonged, dangerous conditions for residents that disrupts transportation and business operations and shuts down schools.
To best prepare, Montgomery County uses a comprehensive approach to winter weather that includes access to commercial weather mapping software and 24/7 access to meteorologists for real-time advice. These resources help MCDOT adequately prepare for winter’s biggest storms, like 2016’s Winter Storm Jonas. You can read all about MCDOT’s preparation and response to this high-impact snow event by reading our case study.
Snowstorms of any severity bring with them varying levels of danger. Some threats are obvious. For example, snow and freezing rain make roads slippery and treacherous.
On the other hand, some of the most deadly threats are less obvious. Did you know that shoveling snow causes approximately 100 deaths per year? Snow shoveling might seem like a necessary activity to clear sidewalks and driveways, but it’s very dangerous for those with heart problems and those who are not used to vigorous exercise.
Watch this 1-minute video below for an overview of other threats posed by winter storms:
Winter Storm Safety Tips
It’s important to take safety messages seriously. In this section, we’ll provide some basic snow safety tips for before, during, and after winter storms courtesy of the National Weather Service.
Before a Winter Storm
The most important thing you can do before a winter storm strikes is to make sure your home, office, and vehicles are stocked with the supplies you might need.
An emergency supply kit for winter weather events should include the following items:
Battery-powered NOAA weather radio
Extra food and water
Extra prescription medicine
Baby items, if necessary, like diapers and formula
First aid supplies
Emergency heat source like a fireplace, wood stove, or space heater
Fire extinguishers & smoke alarm
Extra pet food and warm shelter for pets
Working carbon monoxide detector
Your car emergency kit should include the following:
First aid kit
Winter layers like mittens, hats, and boots
Snow brush and shovel
Sand or kitty litter
Full tank of gas
During a Winter Storm
Now that you have prepared in advance of the storm, here are more safety tips for when a storm actually hits.
If you’re caught outside during a winter storm, the first thing you should do is try to find shelter. While you’re searching, keep dry and cover all exposed body parts to minimize your risk of hypothermia and frostbite.
If you can’t find shelter, build a lean-to, windbreak, or snow cave for protection from the wind. Try to build a fire for warmth and to attract attention. A good way to make your fire warmer is to place rocks around it. They will absorb and reflect heat.
You can melt snow for drinking water, but don’t eat unmelted snow! It will lower your body temperature.
Another good safety tip is to exercise. From time to time, move your arms, legs, fingers, and toes vigorously to keep blood circulating. This will keep you warm. Avoid overexertion and sweating to protect yourself from hypothermia and heart attacks.
In a vehicle
If you’re in a vehicle during a winter storm you’ll want to get to a safe shelter if possible. If you must drive during a storm, make sure your vehicle is clear of ice and snow before you leave and drive slowly. It’s a good idea to let someone know where you’re going and when you’re leaving.
If your vehicle skids, don’t panic. Ease your foot off the gas and turn your wheels in the direction you want the front of the car to go. If your car gets stuck, stay in your vehicle! Run your motor about 10 minute each hour for heat and open the window a little to avoid carbon monoxide poisoning. You should also clear your exhaust pipe.
The safest place to be during a winter storm is indoors, but that doesn’t mean you should relax! Follow these indoor winter storm safety tips:
When using heat from a fireplace or space heater, use safeguards and properly ventilate the area
If your heat goes out:
Close off unneeded rooms, stuff towels or rags in cracks under doors, and close blinds or curtains to keep in some heat
Eat and drink non-caffeinated, non-alcoholic drinks to avoid dehydration
Wear layers of loose-fitting, light-weight, warm clothing
After a Winter Storm
Winter storm danger doesn’t subside once snow stops falling. There are a few things to consider after the storm.
As with the conclusion of any high-impact weather event, make sure you stay informed. Watch the local news for updated information on the weather and road conditions. Check with water and utility companies to ensure everything is safe. Make sure you also leave time for blocked, closed, or icy roads if you will be traveling somewhere.
Make sure you’re wearing weather-appropriate attire (hats, gloves, and jackets) to stay warm when venturing outdoors and be aware of your surroundings. If the storm left behind a heavy accumulation of snow or ice, stay away from trees and rooflines where that snow or ice could fall on you.
And, as we mentioned before, be careful out there shoveling snow! Take frequent breaks and drink plenty of fluids to stay hydrated.
Worst Blizzards in U.S. History
As we mentioned briefly before, winter storms can be deadly. They can also cost hundreds of thousands of dollars.
In the U.S. alone there have been dozens of infamous snowstorms. In this section, we’ll go through the top 5 worst blizzards in U.S. history. These historical snowstorms were extremely dangerous and wreaked havoc.
To view a longer list with the Top 10 Winter Storms, head over to our worst blizzards blog post.
1. The White Hurricane of 1913
The first storm on our list is the “White Hurricane” of 1913 – also known as the worst storm to ever hit the Great Lakes region. Hurricane-force winds created 35-foot waves on November 7-10, 1913.
More than 200 people died and eight ships sunk as a result of the storm. The National Weather Service’s Meteorologist-in-Charge at the time, Richard Wagenmaker, declared the storm “one of the deadliest maritime weather disasters in North American History.”
2. The Great Appalachian Storm of 1950
The second storm on our list is the Great Appalachian Storm of 1950. This storm is one of the most meteorologically unique storms as it was both part-blizzard and part-hurricane.
The devastating cyclone formed on November 24, 1950 in the Appalachian mountains of North Carolina and would become one of the deadliest winter storms of all time, killing 353 people and injuring over 150 others. La Nina conditions helped the storm reach hurricane-force wind with speeds of 110mph and chilling temperatures.
Most of the snowfall occurred in Ohio, with over one foot of snow in some places.
3. The Blizzard of 1978
One of the most catastrophic storms in winter weather history was the Blizzard of 1978. The storm struck New England, New York and New Jersey from February 5-7, 1978.
Also known as ‘Storm Larry’ and ‘The Storm of the Century,’ the blizzard killed over 100 people and injured another 4,500. All economic activity halted and damages amounted to nearly $520 million.
Not only did snow totals break records in various parts of New England, but hurricane-force winds were recorded as well. Many blame inadequate forecasting as a reason behind the high death tolls and economic losses.
4. The Superstorm of 1993
Replacing the Blizzard of ’78 as “The Storm of the Century,” the Blizzard of 1993 was one of the most intense, mid-latitude cyclones ever observed over the Eastern U.S.
High winds knocked out power to over 10 million customers. Storm surge and heavy snow also negatively impacted many areas. Locations in Tennessee and North Carolina measured 60 and 50 inches of snow, respectively. Since the storm moved throughout a densely populated portion of the U.S., many people died as a result: approximately 208.
5. The Blizzard of 1996
The next blizzard from winter weather history to make our list was the Blizzard of 1996.
As one of the most infamous storms in U.S., this nor’easter paralyzed New York and the rest of the East Coast with up to four feet of snow in some areas. Philadelphia accumulated 30.7 inches of snow – which still stands as the record accumulation of snow to date.
The storm killed 154 people. Many died as a result of over-exertion from shoveling snow and other snow-related accidents and economic losses are estimated near the $3 billion mark.
Learn More Weather Basics
Now that you’re a snow expert, it’s time you expanded your meteorological knowledge to other weather events. Luckily, we have all the resources you need! Head over to our Weather 101 page to get started. Pick a topic that interests you and get reading! You’ll be a weather expert in no time.