Public Information Statement
Issued by NWS Omaha/Valley, NE

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Public Information Statement
National Weather Service Omaha/Valley NE
308 AM CDT Tue Mar 27 2018

...2018 Severe Weather Awareness Week for Nebraska/Iowa...

The National Weather Service along with Nebraska Emergency Management
and the Iowa Homeland Security and Emergency Division have declared
March 26 through March 30 as Severe Weather Awareness Week.

The topic for today is Thunderstorms.

A thunderstorm is considered severe when it produces hail that is one inch
in diameter or larger, damaging winds equal to or greater than 58 miles
per hour, or a tornado.

There are numerous aspects of severe thunderstorms that pose a threat to
life and property.  Along with the threat of large hail, damaging winds,
and tornadoes, everyone must also be aware of the possibility of dangerous
lightning and flooding.  Lightning, flooding, and tornadoes will be
discussed later during the week.

Hail is produced in a thunderstorm as rising currents of air, known as
updrafts, carry water droplets to a height where freezing occurs.  Hail
continues to grow inside a thunderstorm until it becomes too
heavy and can no longer be supported by the storm updraft. Once
this occurs, the hailstone falls to the ground. Large hail is an
indication that a thunderstorm is quite intense with a very strong
updraft. The largest hailstone ever recorded in the United States
fell in Vivian, South Dakota with a diameter of 7.9 inches and
circumference of over 18 inches; weighing 1.94 pounds.

Another significant severe weather threat is damaging winds, which can
be caused by an event known as a downburst.  A downburst is a small area
of rapidly descending air beneath a thunderstorm.  Once this descending
air hits the ground, it spreads out in all directions.  Downbursts and the
resulting straight line winds can cause damage comparable to a tornado.

Anytime the threat for severe weather exists, stay updated on the latest
weather information by going to the National Weather Service website,
http://www.weather.gov, or by tuning in to NOAA Weather Radio All Hazards,
or your local television and radio station.  Make sure to watch for signs
for approaching storms, such as darkening skies, increasing winds, flashes
of lightning, and thunder.

For safety information visit www.weather.gov/os/tornado

For more information contact:

Brian Smith
Warning Coordination Meteorologist
National Weather Service Omaha/Valley NE
www.weather.gov/Omaha
402-359-5166

Cathy Zapotocny
Meteorologist
National Weather Service Omaha/Valley NE
www.weather.gov/Omaha
402-359-5166

$$



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