Public Information Statement
Issued by NWS Omaha/Valley, NE

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Public Information Statement
National Weather Service Omaha/Valley NE
608 AM CDT Tue Mar 28 2017

...2017 Severe Weather Awareness Week for Nebraska and Iowa...

The National Weather Service along with Nebraska Emergency Management
and the Iowa Homeland Security and Emergency Division have declared
March 27 through March 31 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 of 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, and 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/severeweather.

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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