A winter storm is an event in which the main types of precipitation are snow, sleet or freezing rain.

Why can winter storms be so dangerous?

Most deaths from winter storms are not directly related to the storm itself.

• People die in traffic accidents on icy roads.
• People die of heart attacks while shoveling snow.
• People die of hypothermia from prolonged exposure to cold.

Everyone is potentially at risk during winter storms. The actual threat to you depends on your specific situation. Recent observations show that:

• Of injuries related to ice and snow:
  • About 70% occur in automobiles.
  • About 25% are people caught out in the storm.
  • Majority are males over 40 years old.
• Of injuries related to exposure to cold:
  • 50% are people over 60 years old.
  • Over 75% are males.
  • About 20% occur in the home.

How do winter storms form?

Just like any other storm at other times of the year, the right combination of ingredients is necessary for a winter storm to develop.

Three basic ingredients are necessary to make a winter storm:

• Cold air. Below freezing temperatures in the clouds and near the ground are necessary to make snow and/or ice.
• Lift. Something to raise the moist air to form the clouds and cause precipitation. An example of lift is warm air colliding with cold air and being forced to rise over the cold dome. The boundary between the warm and cold air masses is called a front. Another example of lift is air flowing up a mountainside.
• Moisture. To form clouds and precipitation. Air blowing across a body of water, such as a large lake or the ocean, is an excellent source of moisture.

Winter Storms

A winter storm is a combination of heavy snow, blowing snow and/or dangerous wind chills. A winter storm is life-threatening.

Blizzards are dangerous winter storms that are a combination of blowing snow and wind resulting in very low visibilities. While heavy snowfalls and severe cold often accompany blizzards, they are not required. Sometimes strong winds pick up snow that has already fallen, creating a ground blizzard.

An ice storm is a storm which results in the accumulation of at least .25” of ice on exposed surfaces. They create hazardous driving and walking conditions. Tree branches and powerlines can easily snap under the weight of the ice.

Lake effect storms are not low pressure system storms. As a cold, dry air mass moves over the Great Lakes regions, the air picks up lots of moisture from the Great Lakes. This air, now full of water, dumps the water as snow in areas generally to the south and east of the lakes.

Snow squalls are brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant. Snow squalls are best known in the Great Lakes region.

Types of Winter Precipitation

SNOW

Most precipitation that forms in wintertime clouds starts out as snow because the top layer of the storm is usually cold enough to create snowflakes. Snowflakes are just collections of ice crystals that cling to each other as they fall toward the ground. Precipitation continues to fall as snow when the temperature remains at or below 0 degrees Celsius from the cloud base to the ground.

• Snow Flurries. Light snow falling for short durations. No accumulation or light dusting is all that is expected.
• Snow Showers. Snow falling at varying intensities for brief periods of time. Some accumulation is possible.
• Snow Squalls. Brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant. Snow squalls are best known in the Great Lakes Region.
• Blowing Snow. Wind-driven snow that reduces visibility and causes significant drifting. Blowing snow may be snow that is falling and/or loose snow on the ground picked up by the wind.
• Blizzards. Winds over 35mph with snow and blowing snow, reducing visibility to 1/4 mile or less for at least 3 hours.

SLEET

Sleet occurs when snowflakes only partially melt when they fall through a shallow layer of warm air. These slushy drops refreeze as they next fall through a deep layer of freezing air above the surface, and eventually reach the ground as frozen rain drops that bounce on impact.

FREEZING RAIN

Freezing rain occurs when snowflakes descend into a warmer layer of air and melt completely. When these liquid water drops fall through another thin layer of freezing air just above the surface, they don't have enough time to refreeze before reaching the ground. Because they are “supercooled,” they instantly refreeze upon contact with anything that that is at or below 0 degrees C, creating a glaze of ice on the ground, trees, power lines, or other objects. A significant accumulation of freezing rain lasting several hours or more is called an ice storm.

Satellite images are very useful tools for determining cloud patterns and movement of winter storms.  By looping a series of satellite pictures together, forecasters can watch a storm's development and movement.

Radar is critical for tracking the motion of precipitation and for determining what kind of precipitation is falling.

The NWS's dual-polarized radars send electromagnetic wave fields at a 45 degree angle, rather than just horizontally.  As these angled fields bounce off an object and are received back at the radar, a computer program separates the fields into horizontal and vertical information.  This 2-D snapshot now gives forecasters a measure of the size and shape of the object.  With this information, forecasters can clearly identify rain, hail, snow, ice pellets and even bugs.  If they know what type of precipitation is falling, they will make more accurate estimates of how much to expect.

Doppler radar can show the wind direction too, which is helpful when forecasting near mountains and large bodies of water.

If the radar shows wind blowing up the mountain (upslope), forecasters know that automatically, one of the ingredients is in place of the development of precipitation: lift. If the radar shows wind blowing over a large section of a body of water (fetch), then they know that another ingredient is present for the formation of precipitation – moisture.

Radar velocities can help identify the location of cold fronts because there is usually a sharp change in wind direction and will show up as a on Doppler radar.

Accurately forecasting winter weather is a complicated process. It starts with a wide network of observing systems such as satellites, Doppler radars and automated surface observing systems. Computer forecast models take this information and estimate what will happen next. Forecasters then use their experience to write and issue forecasts.

Knowing the climatology for a given area is very important to be able to forecast winter weather. Winter storms come in different sizes and are created by different combinations of atmospheric conditions and local geography.

Mid-Atlantic Coast to New England

The classic storm is called a Nor'easter. A low-pressure area off the Carolina coast strengthens and moves north. Wind-driven waves batter the coast from Virginia to Maine, causing flooding and severe beach erosion. The storm taps the Atlantic Ocean's moisture-supply and dumps heavy snow over a densely populated region. The snow and wind may combine into blizzard conditions and form deep drifts paralyzing the region. Ice storms are also a problem. Mountains, such as the Appalachians, act as a barrier to cold air trapping it in the valleys and adjacent low elevations. Warm air and moisture moves over the cold, trapped air. Rain falls from the warm layer onto a cold surface below becoming ice.

Gulf Coast and Southeast

This region is generally not used to snow, ice, and freezing temperatures. Once in awhile, cold air penetrates south across Texas and Florida, into the Gulf of Mexico. Temperatures fall below freezing killing tender vegetation, such as flowering plants and the citrus fruit crop. Wet snow and ice rapidly accumulate on trees with leaves, causing the branches to snap under the load. Motorists are generally unaccustomed to driving on slick roads and traffic accidents increase. Some buildings are poorly insulated or lack heat altogether. Local towns may not have available snow removal equipment or treatments, such as sand or salt for icy roads.

Midwest and Plains

Storms tend to develop over southeast Colorado in the lee of the Rockies. These storms move east or northeast and use both the southward plunge of cold air from Canada and the northward flow of moisture from the Gulf of Mexico to produce heavy snow and sometimes blizzard conditions. Other storms affecting the Midwest and plains intensify in the lee of the Canadian Rockies and move southeast. Arctic air is drawn from the north and moves south across the Plains and Great Lakes. Wind and cold sometimes combine to cause wind chill temperatures as low as 70 degrees below zero. The wind crosses the lakes, tapping its moisture and forming snow squalls and narrow heavy snow bands. This is called “lake-effect snow.”

From the Rockies to the West Coast

Strong storms crossing the North Pacific sometimes slam into the coast from California to Washington. The vast Pacific provides an unlimited source of moisture for the storm. If cold enough, snow falls over Washington, Oregon and California. As the moisture rises into the mountains, heavy snow closes the mountain passes and can cause avalanches. The cold air from the north has to filter through mountain canyons into the basins and valleys to the south. If the cold air is deep enough, it can spill over the mountain ridge. As the air funnels through canyons and over ridges, wind speeds can reach 100 mph, damaging roofs and taking down power and telephone lines. Combining these winds with snow results in a blizzard.

Alaska

Wind-driven waves from intense storms crossing the Bering Sea produce coastal flooding and can drive large chunks of sea ice inland destroying buildings near the shore. High winds, especially across Alaska's Arctic coast, can combine with loose snow to produce a blinding blizzard and wind chill temperatures to 90 degrees below zero! Extreme cold and ice fog may last a week at a time. Heavy snow can impact the interior and is common along the southern coast. With only brief glimpses of the winter sun across the southern horizon, the snow accumulates through the winter months. In the mountains, it builds glaciers, but the heavy snow accumulations can also cause avalanches or collapse roofs of buildings. A quick thaw means certain flooding. Ice jams on rivers can also cause substantial flooding.

An avalanche is a rapid flow of snow down a hill or mountainside. Although avalanches can occur on any steep slope given the right conditions, certain times of the year and types of locations are naturally more dangerous. While avalanches are sudden, there are typically a number of warning signs you can look for or feel before one occurs. In 90 percent of avalanche incidents, the snow slides are triggered by the victim or someone in the victim's party. Avalanches kill more than 150 people worldwide each year. The National Weather Service provides current weather conditions and forecast information to regional avalanche forecast centers that in-turn issue avalanche forecasts. Avalanche warnings and special advisories are included on NWS websites and broadcast over NOAA Weather Radio. Refer to your local avalanche center for current snowpack conditions!

How to Stay Safe

Get Training.

• Know the three factors required for an avalanche:
  • Slope - Avalanche generally occur on slopes steeper than 30 degrees
  • Snowpack - Recent avalanches, shooting cracks, and “whumpfing” are signs of unstable snow.
  • Trigger - Sometimes it doesn’t take much to tip the balance; people, new snow, and wind are common triggers.
• Determine if you are on or below slopes that can avalanche
• Find out if the snow is stable
• Get the Advisory: Refer to your local avalanche center for current snowpack conditions!
• Get the gear...and learn how to use it! Have these three avalanche safety essentials in your pack. :
  • Transceiver: so you can be found if covered by the snow
  • Shovel: so you can dig out your partner
  • Probe: so you can locate someone who has been covered by the snow

Avalanche survival rates plummet after about 15 minutes for victims who do not die from trauma. Saving your partner is up to you! Practicing realistic scenarios beforehand is essential.

Avalanche Warning Signs

The following are a few of the warning signs of unstable snow and possible avalanches:

• You see an avalanche happen or see evidence of previous slides.
• Cracks form in the snow around your feet or skis.
• The ground feels hollow underfoot.
• You hear a "whumping" sound as you walk, which indicates that the snow is settling and a slab might release.
• Heavy snowfall or rain in the past 24 hours
• Significant warming or rapidly increasing temperatures
• You see surface patterns on the snow made by the force of strong winds. This could indicate that snow has been transported and deposited in dangerous drifts that could release.

The most well-known blizzards are winter storms that produce several inches occurring with strong winds that cause blowing snow and whiteout conditions, but not all blizzards happen this way. In the Midwest, ground blizzards develop with little or no concurrent (or new) snowfall. One of the most infamous ground blizzards was the Children's Blizzard of 1888, which killed an estimated 235 people in the Great Plains. This ground blizzard was extremely dangerous because it was preceded by unseasonably warm air, which caused people to let their guard down. Many people ventured outside without proper winter clothing, but the relatively warm weather did not last long. Since then, there have been countless other ground blizzards, many of which were deadly.

The typical ground blizzard occurs when an Arctic cold front moves through the region, causing temperatures to drop and winds to increase quite rapidly, often reaching gusts of 50 to 60 mph. If there are several inches of deep fresh snow on the ground, this strong wind will quickly pick up the snow and create whiteout conditions. Another reason these blizzards are dangerous is the cold temperatures that follow behind the Arctic front. Anyone stranded in their vehicle or forced to walk outside is at risk of frostbite or hypothermia.

Heavy accumulations of ice can bring down trees and topple utility poles and communication towers. Ice can disrupt communications and power for days while utility companies repair extensive damage. Even small accumulations of ice can be extremely dangerous to motorists and pedestrians. Bridges and overpasses are particularly dangerous because they freeze before other surfaces.

Black Ice: Black ice is a deadly driving hazard defined as patchy ice on roadways or other transportation surfaces that cannot easily be seen. It is often clear (not white) with the black road surface visible underneath. It is most prevalent during the early morning hours, especially after snow melt on the roadways has a chance to refreeze over night when the temperature drops below freezing. Black ice can also form when roadways are slick from rain and temperatures drop below freezing overnight.

Ice Jams: Long cold spells can cause rivers and lakes to freeze. A rise in the water level or a thaw breaks the ice into large chunks which become jammed at manmade and natural obstructions. Ice jams can act as a dam, resulting in severe flooding.

Ice Recreation: Ice on lakes and streams can be deadly. Before fishing, skiing, snowmobiling or engaging in any other activities on ice, check with local officials, such as your State Department of Natural Resources, who monitor the body of water. If you see any of the following conditions, do NOT go out on the ice:

• Cracks, holes or breaks in the ice
• Flowing water around the edges, just below the surface, or over the top of the ice
• Ice that appears to have thawed and refrozen

If you decide to venture out on the ice, remember the following guidelines:

• Stay off the ice if it is less than 2 inches thick!
• For ice fishing, ice skating and walking, you need 4 inches or more of ice.
• For snowmobiles and ATVs, you need at least 5 inches.
• To drive a car or small pickup on ice you need at least 8 to 12 inches of ice.
• For medium-sized trucks, there must be at least 12 to 15 inches.

White or “snow” ice is only about half as strong as new, clear ice. Double these thickness guidelines when traveling on white ice. For more information on ice thickness and safety, visit mndnr.gov/icesafety

Frost: Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects fall below 32°F. As with the term "freeze," this condition is primarily significant during the growing season. If a frost period is sufficiently severe to end the growing season or delay its beginning, it is commonly referred to as a "killing frost." Because frost is primarily an event that occurs as the result of radiational cooling, it frequently occurs with a thermometer level temperature in the mid-30s.

Lake effect snow is common across the Great Lakes region during the late fall and winter. Lake Effect snow occurs when cold air, often originating from Canada, moves across the open waters of the Great Lakes. As the cold air passes over the unfrozen and relatively warm waters of the Great Lakes, warmth and moisture are transferred into the lowest portion of the atmosphere. The air rises, clouds form and grow into narrow band that produces 2 to 3 inches of snow per hour or more.

Wind direction is a key component in determining which areas will receive lake effect snow. Heavy snow may be falling in one location, while the sun may be shining just a mile or two away in either direction. The physical geography of the land and water is also important. National Weather Service meteorologists consider these factors as well as others when forecasting lake effect snow.

A Nor’easter is a storm along the East Coast of North America, so called because the winds over the coastal area are typically from the northeast. These storms may occur at any time of year but are most frequent and most violent between September and April. Some well known Nor’easters include the notorious Blizzard of 1888, the “Ash Wednesday” storm of March 1962, the New England Blizzard of February 1978, the March 1993 “Superstorm” and the recent Boston snowstorms of January and February 2015. Past Nor’easters have been responsible for billions of dollars in damage, severe economic, transportation and human disruption, and in some cases, disastrous coastal flooding. Damage from the worst storms can exceed a billion dollars.

Nor’easters usually develop in the latitudes between Georgia and New Jersey, within 100 miles east or west of the East Coast. These storms progress generally northeastward and typically attain maximum intensity near New England and the Maritime Provinces of Canada. They nearly always bring precipitation in the form of heavy rain or snow, as well as winds of gale force, rough seas, and, occasionally, coastal flooding to the affected regions. The heavily populated region between Washington D.C., Philadelphia, New York and Boston, the “I-95 Corridor,” is especially impacted by Nor’easters.

The U.S. East Coast provides an ideal breeding ground for Nor’easters. During winter, the polar jet stream transports cold Arctic air southward across the plains of Canada and the United States, then eastward toward the Atlantic Ocean where warm air from the Gulf of Mexico and the Atlantic tries to move northward. The warm waters of the Gulf Stream help keep the coastal waters relatively mild during the winter, which in turn helps warm the cold winter air over the water. This difference in temperature between the warm air over the water and cold Arctic air over the land is the fuel that feeds Nor’easters.

Weather forecasters at NWS local forecast offices around the country and at the National Centers for Environmental Prediction near Washington, D.C., monitor conditions conducive for Nor’easters, especially during the fall and winter. When they see conditions are favorable in the upcoming days, forecasters may issue winter storm, blizzard, high wind and coastal flood watches to alert the public that some of the worst effects of Nor’easters might be possible. If conditions are imminent, those watches are changed to warnings.

The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term "vortex" refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream (see graphic above). This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States. The one that occurred January 2014 is similar to many other cold outbreaks that have occurred in the past, including several notable colder outbreaks in 1977, 1982, 1985 and 1989.

There are several things the polar vortex is NOT. Polar vortexes are not something new. The term “polar vortex” has only recently been popularized, bringing attention to a weather feature that has always been present. It is also not a feature that exists at the Earth’s surface. Weather forecasters examine the polar vortex by looking at conditions tens of thousands of feet up in the atmosphere; however, when we feel extremely cold air from the Arctic regions at Earth’s surface, it is sometimes associated with the polar vortex. This is not confined to the United States. Portions of Europe and Asia also experience cold surges connected to the polar vortex. By itself, the only danger to humans is the magnitude of how cold temperatures will get when the polar vortex expands, sending Arctic air southward into areas that are not typically that cold.

In short, there is no cause to be alarmed when you hear about the polar vortex, but you should be prepared for colder temperatures. Check the forecast for your area on weather.gov to ensure you are dressed appropriately. It is also a good idea to check the items in your home and car emergency kits at the beginning of each winter season to ensure you are prepared for any type of hazardous winter weather.

What are snow squalls?

Snow squalls, often associated with strong cold fronts, are a key wintertime weather hazard. They move in and out quickly, and typically last less than an hour. The sudden white-out conditions combined with falling temperatures produce icy roads in just a few minutes. Squalls can occur where there is no large-scale winter storm in progress and might only produce minor accumulations. Snow squalls can cause localized extreme impacts to the traveling public and to commerce for brief periods of time. Unfortunately, there is a long history of deadly traffic accidents associated with snow squalls. Although snow accumulations are typically an inch or less, the added combination of gusty winds, falling temperatures and quick reductions in visibility can cause extremely dangerous conditions for motorists.
 

 

What is the difference between a snow squall and a snow storm?

The difference between a snow squall and a snowstorm is the duration of the event. Snow squalls are usually very short-lived (on the order of 30-60 minutes) and extremely intense. A snow storm could last for several hours or even days.


Valentine’s Day Squall in 2015, Port Matilda, PA.  Courtesy: Greg DeVoir, NWS

Snow Squall Warnings

Snow squall warnings are short-fused and focused on distinct areas (like tornado and severe thunderstorm warnings). These warnings provide critical, highly localized life-saving information. If a snow squall warning is issued for your area, avoid or delay motor travel until the squall passes through your location. Read the Impact-Based Snow Squall Warnings factsheet.

Actions to Take

If a snow squall warning is issued for your area, avoid or delay motor travel until the squall passes through your location. There truly is no safe place on the highway during a snow squall. However if you are already in transit and cannot exit the road in time, reduce your speed, turn on your headlights and hazard lights and allow plenty of distance between you and the car in front of you. It’s also best not to slam on your brakes.  With slick/icy roads, this could contribute to the loss of vehicle control and also increase the risk of a chain reaction crash.

Follow weather.gov to get the latest forecasts and warnings before you start your car to travel. For tips on how to stay safe before, during and after a winter weather, bookmark our Winter Weather Safety page. Prior to traveling, take steps to prepare your vehicle and have an emergency kit for your car. Bottom line, follow weather.gov to get the latest warnings before you travel this winter.

Heavy snow can immobilize a region and paralyze a city, stranding commuters, closing airports, stopping the flow of supplies, and disrupting emergency and medical services. The weight of snow can cause roofs to collapse and knock down trees and power lines. Homes and farms may be isolated for days and unprotected livestock may be lost. In the mountains, heavy snow can lead to avalanches. The cost of snow removal, repairing damages, and the loss of business can have severe economic impacts on cities and towns. See weather.gov for the latest forecast.

• Blizzard: Sustained winds or frequent gusts of 35 mph or more with snow and blowing snow frequently reducing visibility to less than a quarter mile for 3 hours or more.
• Blowing Snow: Wind-driven snow that reduces visibility. Blowing snow may be falling snow and/or snow on the ground picked up by the wind.
• Snow Squalls: Brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant.
• Snow Showers: Snow falling at varying intensities for brief periods of time. Some accumulation is possible.
• Flurries: Light snow falling for short durations with little or no accumulation.
• Avalanche: A mass of tumbling snow. More than 80 percent of midwinter avalanches are triggered by a rapid accumulation of snow and 90 percent of those avalanches occur within 24 hours of snowfall. An avalanche may reach a mass of a million tons and travel at speeds up to 200 mph.

Are You Prepared for Winter Weather?

When winter temperatures drop significantly below normal, staying warm and safe can become a challenge. According to a 2014 CDC National Health Statistics Report, during 2006–2010, about 6,600 U.S. residents died from exposure to excessive natural cold, hypothermia, or both.

What is extremely cold weather? The definition of extreme cold can vary. After all, what is cold to one person may not feel that cold to another. People who live in regions with relatively few days of freezing temperatures are not accustomed to them when they go to colder areas.

Whenever temperatures drop below what feels lower than normal to you—and as wind speed increases—heat can leave your body more rapidly and leave you at risk of health problems.

Extremely cold temperatures are often accompanied by winter storms, so in addition to the risks of the cold, you may also have to cope with power failures and icy roads. Staying indoors as much as possible can reduce the risks of car crashes and falls on the ice, but you may also face indoor hazards. Many homes will be too cold—either due to a power failure or because the heating system isn’t adequate for the weather. When people must use space heaters and fireplaces to stay warm, the risk of household fires increases, as well as the risk of carbon monoxide (CO) poisoning.

If you are prepared for the hazards of winter, you will be more likely to stay safe and healthy when temperatures start to fall.

• Winterize your home. Install weather stripping, insulation, and storm windows.
• Get your car ready for cold weather. Service the radiator and maintain antifreeze level; check tire tread or, if necessary, replace tires with all-weather or snow tires. Keep an emergency kit in your car including blankets, food and water, first aid, and other items you may need if you are stranded
• Be prepared for weather-related emergencies, including power outages.
• Prevent CO poisoning. Install a CO detector and check that it has a working battery. Have your heating system checked by a qualified professional. Never use a gas range or oven to heat your home.
• Take precaution when spending time outdoors. Wear appropriate outdoor clothing and be aware of the wind chill factor. Check weather reports, telling someone where you are going to be (if long drive or ice fishing). Always have a fully charged cellphone and carry a portable recharger, if possible
• Be aware of current and forecast weather conditions when planning for travel.
• Learn how to avoid, spot and treat frostbite and hypothermia.
• If you have pets, bring them inside. If you cannot bring them inside, provide adequate, warm shelter and unfrozen water to drink.

Be safe during winter weather.

Winter storms can be just as hazardous as any other type of weather, and it's equally important to be prepared. Winter storms can last days, make travel impossible, and knock out power and communication systems. Don't underestimate the power of winter storms, and be sure to take the necessary steps in order to protect yourself.

Ready...Most hazardous weather is forecast days in advance. Begin your preparations by paying attention to the weather forecast. The Key Impacts Graphic is a great product issued by the National Weather Service that highlights the potential for hazardous weather over the next seven days.

Set...If a winter storm is possible, then a Winter Storm Watch will be issued. This means that conditions are favorable for a winter storm to occur, but some aspects such as location, timing, and snow amounts may still be uncertain. Pay attention and listen to your NOAA weather radio or tune in to your local broadcast media for the latest information. Start gathering supplies and have a plan in place that includes what you will do during the storm.

Go! As the event becomes imminent, then the Winter Storm Watch will be upgraded to a Winter Weather Advisory or a Winter Storm Warning. This indicates a threat to life and property, and travel will become dangerous if not impossible.

Staying indoors and off the roads

Staying indoors and off the roads is a great start in protecting yourself in the event of a winter storm, but you do face hazards indoors as well. Take extra steps to ensure you are properly heating your home.

• Have extra blankets and winter coats
• If using a space heater, use one with an automatic shut-off switch and keep it away from flammable materials
• Do not plug your space heater into an extension cord
• Ensure any cords associated with a space heater are not a tripping hazard
• If using a fireplace or wood stove, be sure it is properly vented
• Do not leave children unattended with space heaters or fireplaces

Power outages are a common hazard during a winter storm. If you experience a power outage, use a battery-powered flashlight or lantern. If you use candles, do not leave them unattended as they can become a fire hazard.

Extreme cold often accompanies winter storms which can wreck havoc on water pipes in your home. When you're expecting very cold temperatures, leave water taps on a drip to prevent freezing. Allow heat to reach your pipes by leaving cabinet doors open. If your pipes do freeze, do not try to unfreeze them with a torch. Use an electric hair dryer to slowly thaw them.

If you must travel

If you must travel, be sure to check road conditions before you leave. Do not travel alone and keep an emergency kit in your car in case you get stranded. Keep your gas tank full. If you get stuck, pull over to the side of the road and stay in your car. Even a short walk during a winter storm can be dangerous.

Can it ever be too cold to snow?

It rarely snows when the temperature drops below zero degrees Fahrenheit because the atmosphere is too stable. One of the ingredients for snow is enough lifting of saturated air that snow can develop aloft and fall to reach the surface. When it is said, “it is too cold to snow,” in reality it means there is not enough lifting of air to cause snow to reach the surface. Even at very cold surface temperatures, significant snowfall can occur. Intense lifting can produce significant precipitation, even at very low temperatures. The temperature higher in the atmosphere can be much warmer than the air temperature at the surface, and that warm air aloft can hold more moist air than the colder air at the surface. And, moisture can be transferred into the area where lifting is occurring through advection (the horizontal movement of an air mass).

What is thundersnow?

Although thunderstorms are less common in the winter, sometimes lightning can occur within snowstorms and is called thundersnow. Thundersnow can be found where there is relatively strong instability and abundant moisture above the surface, such as above a warm front. Thundersnow is sometimes observed downstream of the Great Salt Lake and the Great Lakes during lake-effect snowstorms too.

How many inches of snow equals one inch of rain?

On average, thirteen inches of snow equals one inch of rain in the US, although this ratio can vary from two inches for sleet to nearly fifty inches for very dry, powdery snow under certain conditions.

What is a nor'easter?

The official definition of a “Nor'easter” is a strong low pressure system that affects the Mid-Atlantic and New England states. It can form over the land of the eastern U.S. or over the Atlantic coastal waters. These winter events are notorious for producing heavy snow, rain, and tremendous waves that crash onto Atlantic beaches, often causing beach erosion and structural damage. Wind gusts associated with these storms can exceed hurricane force in intensity. A nor'easter gets its name from the continuously strong northeasterly winds blowing in from the ocean ahead of the storm and over the coastal areas. What makes them so strong is the warm and moist air from the Atlantic that feeds the storm, causing it to grow explosively.

What is white lightning?

White lightning is a colloquial term for thunderstorms occurring with snow.

Are microbursts or downbursts present in snow squalls?

We have not heard of this happening. Evaporation of snow in such storms typically doesn't produce enough cooling to drive a downdraft circulation in the squall.

What are the important winter weather notices?

Blizzard Warning: Issued when winds of 35 mph or greater are combined with blowing and drifting snow with visibilities of ¼ mile or less. Seek indoor shelter immediately and stay indoors until the severe conditions end.

Winter Storm Warning: Issued when a combination of hazardous winter weather in the form of heavy snow, heavy freezing rain, or heavy sleet is imminent or occurring. Winter Storm Warnings are usually issued 12 to 24 hours before the event is expected to begin.

Winter Storm Watch: Issued 12-48 hours in advance of the onset of severe winter conditions. The watch may or may not be upgraded to a winter storm warning, depending on how the weather system moves or how it is developing.

Winter Storm Outlook: Issued prior to a Winter Storm Watch. The Outlook is given when forecasters believe winter storm conditions are possible and are usually issued 3 to 5 days in advance of a winter storm.

Winter Weather Advisories: Issued for accumulations of snow, freezing rain, freezing drizzle, and sleet which will cause significant inconveniences and, if caution is not exercised, could lead to life-threatening situations.

Lake Effect Snow Warning: Issued when heavy lake effect snow is imminent or occurring.

Lake Effect Snow Advisory: Issued when accumulation of lake effect snow will cause significant inconvenience.

Wind Chill Warning: Issued when wind chill temperatures are expected to be hazardous to life within several minutes of exposure.

Wind Chill Advisory: Issued for a wind chill situation that could cause significant inconveniences, but do not meet warning criteria. Criteria for issuing Windchill Warnings and Advisories are set locally.

Dense Fog Advisory: Issued when fog will reduce visibility to ¼ mile or less over a widespread area.

Snow Flurries: Light snow falling for short durations. No accumulation or light dusting is all that is expected.

Snow Showers: Snow falling at varying intensities for brief periods of time. Some accumulation is possible.

Blowing Snow: Wind-driven snow that reduces visibility and causes significant drifting. Blowing snow may be snow that is falling and/or loose snow on the ground picked up by the wind.