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STRONG
STRAIGHT-LINE WINDS AND LARGE HAIL ARE MAJOR WEATHER THREATS IN THE INLAND NORTHWEST
Across eastern Washington
and north Idaho, thunderstorms can develop by midday and carry on into the evening
hours. Threats from thunderstorms can be many, ranging from tornadoes, flooding
and lightning. Tornadoes can be the front-page headline in newspapers or the
top story on the evening news, but damaging straight-line winds of "tornado
force" can also injure and kill animals and humas.
STRAIGHT
LINE WINDS
Barn Damage near Lewiston, ID due to straight-line winds 5/29/03.
Downburst winds from a thunderstorms
usually results when an area of air within the storm is cooled by chilly raindrops
or hailstones, or by evaporation of the raindrops, which quickly cools the air.
This pocket of cooled air, heavier than surrounding air, accelerates downward
to the ground. As the cool air slams into the ground, it spreads out from the
area of impact. The varied terrain in our region can enhance downburst winds.
This process, in extreme
cases, can cause winds higher than 100 mph! Weather forecasters call these bursts
of wind "microbursts" if they are less than 2 1/2 miles across and
"macrobursts" if they are greater than 2 1/2 miles across. These downbursts
of air can be very hazardous and even life-threatening to pilots and can cause
extensive damage, injuries and fatalities at ground level as well.
Try to get indoors during
all thunderstorm activity. High winds can suddenly develop, which can cause
things on the ground to become swift moving, airborne missiles, which can injure
or kill.
LARGE
HAIL
Large hail to 1 1/2 inches near Newport, WA on 7/10/03.
Hail is another thunderstorm
threat that often occurrs across the Inland Northwest. Hail forms within thunderstorms.
As liquid water freezes in the cold mid and upper levels of the storm, the ice
is kept aloft by strong updraft winds for a time. Then when they become too
large to be kept aloft by the updrafts, they cascade to the ground.
Hailstones vary from pea-size
(about 3/8 of an inch in diameter) to larger than grapefruits (nearly 5 inches
in diameter). Hailstones can produce tremendous damage to farm crops, either
as large hailstones or as concentrated fall of small hailstones that accumulates
to a depth of several inches. Large hail can easily damage vehicles and buildings,
and can be life-threatening to animals and people.
Again, try to get indoors
during all thunderstorms. A fall of small hail can suddenly change to a fall
of very large ice missles, than can injure or even kill.
Remember, tune into NOAA
Weather Radio, the Weather Channel, or your local radio or TV stations for further
details. At any location you find yourself, plan on how be safe when thunderstorms
develop.
For more information on
strong winds and hail, visit the National Weather Service Severe
Awareness web page.
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www.weather.gov 
