Severe Storms/Winter Storms

This page is for the Severe Storms topic of the Meteorology event.

Overview
Snow is less dense than liquid by a factor of approximately ten in temperatures just under freezing. In other words, 1 inch of rain would be about 10 inches of snow. Therefore, snow storms can be very problematic, especially in areas that are not used to getting heavy snow. More than 6 inches of snow will be a problem anywhere. Some of the key dangers of snow storms include hypothermia, frostbite, car wrecks, or avalanches if near or on a mountain.

In order for a snow storm to be classified as a "blizzard" it must have all of the following characteristics: Storms are listed below.
 * Visibility reduced to less than 1/4 mile
 * Winds greater than 35 miles per hour
 * Last for a long period of time such as three hours

Blizzards
A blizzard has winds of 35 mph (or more) and visibility of less than a 1/4 mile for more than 3 hours. Once these conditions are expected, the NWS (National Weather Service) will issue a "blizzard warning." When these conditions are expected to not occur at the same time, but that one or two will, a "Winter Storm Warning" or "Heavy Snow Warning" may be issued. A "watch" is issued when severe winter weather is probable because of the conditions, but not necessarily imminent, and an "advisory" is issued when less-serious conditions are occurring, imminent, or there is a high probability.

Blizzards most often occur in the upper Midwest and Great Plains of the United States because of the flat land. Conditions of a blizzard develop on the northwest side of an intense storm system. The lower pressure in the storm and the higher pressure to the west's difference creates a tight pressure gradient, meaning a difference in pressure between two locations resulting in very strong winds. The winds can then pick up snow off the ground or blow falling snow creating low visibility and a chance for significant drifting of snow. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Strong winds/cold temperatures combine to create danger, such as the wind chill factor which can drop to –60F during blizzards in the Midwest.

Hazards
A blizzard's main dangers are its strong winds, freezing temperatures, and deep snow.
 * Find shelter indoors
 * Stay away from windows and doors
 * Keep a car in good working condition, with a gas tank at least half-full, good winter tires, and snacks and water stored within
 * If you're stuck in a car with the engine running to stay warm, keep the windows open a little bit. This will let poisonous carbon monoxide escape from the inside of the car.
 * Keep extra food and water, a flashlight, a battery-powered radio, and, if possible, a cell phone with you
 * If trudging through deep snow, keep moving. Do not lie down to rest.
 * If caught outdoors, use clothing to cover as much skin as possible.
 * Use public transportation if going outside is necessary
 * Listen to the radio/call state highway patrol
 * Avoid shoveling too much snow at once

Nor'easters
A northeaster is a macro-scale cyclone that blows from the East Coast of North America. The economic- and transportation-related damage can exceed a billion dollars. During winter, the polar jet stream moves Arctic air to the east area of the U.S. where warm air is moving upwards. Winds circulate counter-clockwise around a low-pressure center.

Famous Nor'easters
 * Blizzard of 1888
 * “Ash Wednesday” storm of March 1962
 * New England Blizzard of February 1978
 * March 1933 “Superstorm”
 * Boston snowstorms of January and February 2015.

Lake-Effect Snow
This is a very common occurrence across the Great Lakes during late fall and winter. It occurs when cold air from Canada moves across the waters of the Great Lakes, where the moisture transfers to the lowest part of the atmosphere. The warm air rises and leads to cloudiness and snow. It usually takes the form of narrow bands characterized by intense snowfall and limited visibility. Sometimes sunny skies can quickly be replaced by thus blinding and wind-driven snowfall in minutes. It is extremely dangerous to motorists.

Other than the Great Lakes, the only places these storms occur are at the east shore of Hudson Bay and along the west coasts of the Japanese islands of Honshu and Hokkaido.

Hail
Updrafts in thunderstorms carry raindrops up into very cold places in the atmosphere and freeze, creating hail. It can be dangerous to aircrafts, homes, people, livestock, and cars. The number of times a hailstone traveled to the top of the cloud can be counted in the layers. The stones can melt and refreeze creating strange shapes. Once the hail can no longer be supported, it begins to fall. Hail swaths are where hail falls a lot, sometimes requiring snow plows. Radars, such as the Doppler-radar, can detect hail as looking like very, very heavy rainfall. Dual-polarization radar technology also can detect it.

Freezing Rain
Liquid raindrops in a layer of warm air high above the ground fall into a layer of freezing cold air right above the ground, forming freezing rain. When the layer of freezing air is very thin, the warm raindrops don't have enough time to freeze and freeze upon reaching the ground. Whatever the drops land on gets coated in a layer of ice.

Freezing rain can be extremely dangerous, since the result is a layer of ice instead of snow. They can create slick spots on the roads and put weight on tree branches and power lines, which can cause them to snap. Even for places that are accustomed to snow storms, as little as 1 cm can completely paralyze a city. Dangers including driving, telephone and electrical wire damage, and entire crops can be destroyed.

Sleet
Sleet (or ice pellets) is made of small, translucent balls of ice. They are rain drops that have frozen before they reached the ground, which occurs when the layer of cold air is thicker than it is for freezing rain. When a layer of subfreezing air near the ground goes high enough, raindrops freeze into little balls of ice before reaching the ground. These pellets of ice usually bounce after hitting the ground or other hard surfaces. It can sometimes be accompanied by freezing rain.

A Winter Storm Warning is issued for sleet or a combination of sleet and snow based on total accumulation, which is locally defined by area.

Snow
Snow is precipitation in the form of ice crystals. It comes from clouds that are below freezing, where water vapor condenses in the atmosphere directly into ice, skipping the liquid stage. It grows into a snow crystal and falls to Earth. Snowflakes are classified as clusters of ice crystals that fall from a cloud. Graupel, sleet, hail, and snowflakes are all considered forms of snow.

Snow is composed of frozen water, meaning it technically can be classified as a mineral.

Rain
Rain is liquid drops of water that fall to the ground and don't freeze. Water condensed in clouds must be heavy enough to fall from clouds, and droplets often collide with others or grow as water condenses out of the air into the droplet until the droplet is large enough to fall. Precipitation that falls to earth in drops more than 0.5 mm in diameter.

Frontal rain forms when two air masses meet, e.g. when warm air cools and condenses. Orographic rain is made because of clouds that form because of topography, where high ground forces moist cool air up. It is most likely to occur near mountains with westerly prevailing winds.

Disaster Supply Kits
Disaster kits are an important part of disaster preparedness. The following are possible items to include in a disaster supply kit for a location prone to severe winter storms.


 * Water, one gallon of water per person per day, for drinking and sanitation
 * Non-perishable food (at least a three-day supply) and can opener if needed
 * Battery-powered radio and a NOAA Weather Radio with tone alert and extra batteries for both
 * Flashlight and extra batteries
 * First Aid kit
 * Whistle to signal for help
 * Moist towelettes, garbage bags, and plastic ties for personal sanitation
 * Portable dishes, liquid dish soap, and disinfectant
 * Dust masks
 * Plastic sheeting and duct tape to shelter-in-place
 * Wrench or pliers to turn off utilities
 * Warm clothes and blankets
 * Infant formula and diapers, if applicable
 * Medical records and supplies, if applicable
 * Pet supplies
 * Pet first-aid kit and guide book (ask your vet what to include, or visit the ASPCA Store to buy one online)
 * 3-7 days-worth of canned or dry food (be sure to rotate every two months) and feeding dishes
 * Disposable litter trays (aluminum roasting pans are perfect) and litter or paper toweling
 * Extra collar/harness and leash
 * Bag(s) or carrier(s)
 * Medical records and supplies, if applicable

Special Topic for 2017
''Note: Parts of this section closely resemble external links. It should be rewritten and the external link should be provided separately for additional research.''

From 1/22/16 through 1/24/2016, the category 5 blizzard (first category 5 blizzard since '11 Groundhog Day Blizzard) produced up to 3 ft of snow in parts of the Mid-Atlantic and Northeast United States. This blizzard was a category 5 "extreme" event for the Northeast on the Regional Snowfall Index, and a Category 4 for the Southeast. Evolving from a shortwave trough, the system consolidated into a defined low-pressure area on 1/21/2016 over Texas. Meteorologists claimed that this could be a historic blizzard and quickly indicated the storm could produce more than 2 ft of snow across the Mid-Atlantic region. From January 20 through 22, eleven states and the District of Columbia declared a state of emergency in anticipation of significant snowfall and blizzard conditions. More than 13,000 flights were canceled in relation to the storm, and a travel ban was instituted for New York City and Newark, New Jersey for January 23–24.

Ice and snow covered roads led to accidents across the region, several of which resulted in deaths and injuries. At least 55 people were killed in storm-related incidents: 12 in Virginia, 9 in Pennsylvania, 6 in New Jersey, 6 in New York, 6 in North Carolina, 4 in South Carolina, 3 in Maryland, 3 in Washington, D.C., 1 in Arkansas, 1 in Delaware, 1 in Georgia, 1 in Kentucky, 1 in Massachusetts, and 1 in Ohio.


 * Number of people affected: approximately 103 million people, 33 million people under blizzard warnings.
 * Nicknames: Winter Storm Jonas, Snowzilla.
 * Peak Accumulation: 66 in (170 cm) on Mount Mitchell, North Carolina.
 * Costs: Between $500 million and $3 billion