Ohio Committee for Severe Weather Awareness Winter Weather Terms

Winter Severe/Hazardous Weather Terms

From NOAA and the National Weather Service

The National Weather Service (NWS) is responsible for issuing winter storm warnings, watches and advisories to alert the public when dangerous winter conditions are expected.

Basic Key Winter Terms:

Freezing Rain - Rain that freezes when it hits the ground, creating a coating of ice on roads, walkways, trees and power lines.

Sleet - Rain that turns to ice pellets before reaching the ground. Sleet also causes moisture on roads to freeze and become slippery.

Snow Squall - An intense fall of accumulating snow, reducing visibility significantly and often accompanied by increased winds.

Wind Chill - A measure of how cold people feel due to the combined effect of wind and cold temperatures. The wind chill index is based on the rate of heat loss from exposed skin. Both cold temperatures and wind remove heat from the body; as the wind speed increases during cold conditions, a body loses heat more quickly. Eventually, the internal body temperature also falls and hypothermia can develop. Animals can also feel the effects of wind chill.

NOAA Winter Outlook (December 2021 - February 2022)

Winter Storm Warnings: Take Action!

Blizzard Warnings are issued for frequent gusts greater than or equal to 35 mph accompanied by falling and/or blowing snow, frequently reducing visibility to less than a quarter mile for three hours or more. A Blizzard Warning means severe winter weather conditions are expected or occurring. Falling and blowing snow with strong winds and poor visibilities are likely, leading to whiteout conditions making travel extremely difficult. 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.

Winter Storm Warnings are issued for a significant winter weather event including snow, ice, sleet or blowing snow or a combination of these hazards. Travel will become difficult or impossible in some situations. Delay your travel plans until conditions improve.

Ice Storm Warnings are usually issued for ice accumulation of around 1/4 inch or more. This amount of ice accumulation will make travel dangerous or impossible and likely lead to snapped power lines and falling tree branches. Travel is strongly discouraged.

Wind Chill Warnings are issued for a combination of very cold air and strong winds that will create dangerously low wind chill values. This level of wind chill will result in frostbite and lead to hypothermia if precautions are not taken. Avoid going outdoors and wear warm protective clothing if you must venture outside.

Snow Squall Warnings (SQWs) are issued to protect lives and property. Weather Forecast Office forecasters issue SQWs to provide the public with advance notice of intense, but limited duration, periods of moderate to heavy snowfall, accompanied by gusty surface winds resulting in reduced visibilities and whiteout conditions.

Watches: Be Prepared

Winter Storm Watches are issued when conditions are favorable for a significant winter storm event (heavy sleet, heavy snow, ice storm, heavy snow and blowing snow or a combination of events.)

Wind Chill Watches are issued when there is the potential for a combination of extremely cold air and strong winds to create dangerously low wind chill values.

Advisories: Be Aware

Winter Weather Advisories are issued when snow, blowing snow, ice, sleet, or a combination of these wintry elements is expected but conditions should not be hazardous enough to meet warning criteria. Be prepared for winter driving conditions and possible travel difficulties. Use caution when driving.

Wind Chill Advisories are issued when low wind chill temperatures are expected but will not reach local warning criteria. Extremely cold air and strong winds will combine to generate low wind chill readings. If you must venture outdoors, take precautions against frostbite and hypothermia.

Winter Product Criteria

Winter Storm

Winter Storm Watch/Warning - 6 inches of snow or 1/2 inch of sleet in 12 hours; 8 inches of snow in 24 hours; 4 inches of snow or 1/2 inch of sleet in 12 hours; or 6 inches of snow in 24 hours

Winter Weather Advisory - 3 inches of snow or under 1/2 inch of sleet in 12 hours; falling and/or blowing snow reducing visibility to 1/4 mile or less, with winds of 34 mph or less; significant black ice conditions with 2 inches of snow or under 1/2 inch of sleet in 12 hours; falling and/or blowing snow reducing visibility to 1/4 mile or less, with winds of 34 mph or less; significant black ice conditions

Freezing Rain

Ice Storm Warning - Ice accumulation of 1/4 inch or greater in 24 hours

Winter Weather Advisory - Ice accumulation of under 1/4 inch

Wind Chill

Wind Chill Watch/Warning - Wind chill of -25˚F or less with wind of 10 mph or greater

Wind Chill Advisory - Wind chill of -10˚F to -24˚F with wind of 10 mph or greater

What is the Polar Vortex?

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 also is 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 El Niño and La Niña?

El Niño and La Niña are opposite phases of a natural climate pattern across the tropical Pacific Ocean that swings back and forth every three to seven years, on average. Together, they are called ENSO (pronounced "en-so"), which is short for El Niño-Southern Oscillation.

The ENSO pattern in the tropical Pacific can be one of three sates: El Niño, Neutral, or La Niña. El Niño (the warm phase) and La Niña (the cool phase) lead to significant differences from the average ocean temperatures, winds, surface pressure and rainfall across parts of the tropical Pacific. Neutral indicates that conditions are near their long-term average.

El Niño and La Niña alternately warm and cool large areas of the tropical Pacific - the world's largest ocean - which can significantly influences where and how much it rains there. The primary location of moist, rising air (over the basin's warmest water) is centered over the central or eastern Pacific during El Niño and over Indonesia and the western Pacific during La Niña.

This shift disrupts the atmospheric circulation patterns that connect the tropics with the middle latitudes, which in turn modifies the mid-latitude jet streams. By modifying the jet streams, ENSO can affect temperature and precipitation across the United States and other parts of the world. The influence on the U.S. is strongest during the winter (January-March), but lingers into early spring.

During El Niño, the southern tier of Alaska and the U.S. Pacific Northwest tend to be warmer than average, whereas the U.S. southern tier of state - from California to the Carolinas - tends to be cooler and wetter than average. During La Niña, these deviations from the average are almost reversed.

The influence of El Niño and La Niña in some parts of the U.S. and the rest of the world can be so strong that they increase the odds of "extreme weather events" - phenomena that rank in the highest or lowest 10 percent compared to historical observations.

El Niño and La Niña: Frequently Asked Questions