National Weather Service United States Department of Commerce

Heavy Rains and Potential for Flash Floods

Severe thunderstorms with damaging winds and heavy rains will be possible from the Ohio Valley to the Northeast Tuesday. In addition, heavy rains possible in the central Plains and southern Rockies. Heavy rain threat moves into the southern Mid-Atlantic Wednesday. Dry conditions remain out west where isolated dry thunderstorms could exacerbate ongoing fires and start new fires. Read More >

Severe Weather Awareness Week Banner

Monday Tuesday Wednesday Thursday Friday
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April 24th - 28th, 2017 is Severe Weather Awareness Week in Pennsylvania


 

Today's Topic: Tornadoes!

Monday's Activities:

Click any Topic to Expand or Contract

1. Learn about Tornadoes.
2. How common are Tornadoes in Pennsylvania?
3. What is the EF-Scale?
4. Have a Safety Plan!
Daily Safety Message:  
Our topic for today is "Tornadoes and Tornado Safety."

We will cover the difference between a Tornado Watch and a
Tornado Warning, and give you tips on what to do when a watch 
or warning is issued for your location.

What is a tornado? 

A tornado is a violently rotating column of air in contact with the 
ground. The wind speeds inside a tornado range from under 100 miles 
an hour up to 300 miles an hour. They can travel with a forward 
speed as fast as 70 mph, and can destroy virtually everything in 
their path.

While most tornadoes that occur in Pennsylvania are not as strong as 
their counterparts in the plains, strong and damaging tornadoes can 
and do occur here. In fact, Pennsylvania ranks in the top 25 for 
tornado occurrence in the United States, averaging twenty tornadoes 
per year. Between May 31st and June 2nd of 1998, Pennsylvania was 
hit by 40 tornadoes, some of which had wind speeds over 200 mph.

What does a Tornado Watch mean?

A Tornado Watch is issued by the National Weather Service in order 
to alert you that severe thunderstorms are expected to develop,  
And to highlight that those storms have the potential to produce 
tornadoes. A Tornado Watch covers a very wide area, generally about 
the size of a state. A Tornado Watch will last for several 
hours, expiring only when the threat of thunderstorms is expected 
to end.

What should you do when a Tornado Watch is issued?

Go about your normal activities, but watch the sky around you for
developing storms. Periodically listen to NOAA Weather Radio or
media outlets for updates and possible warnings.

Know which county you live in, and which ones border your 
community. Think of a safe place to move to quickly if a tornado 
warning is issued for your location, or if thunderstorms approach.

What does a Tornado Warning mean?

A Tornado Warning is issued when meteorologists spot a developing
tornado using Doppler radar, or when a tornado has been sighted
by trained Skywarn spotters. The warning means a tornado is going
to move through your area soon, so you need to take immediate
action to protect your life and property.

Tornado Warnings issued by National Weather Service meteorologists 
typically cover areas smaller than one county, and for a duration 
of generally less than one hour. In the text of the warning 
statement, we try to make a specific list of towns that are likely 
to be in the path of the tornado. You should listen to hear if 
communities or landmarks near you are mentioned in the warning.

What you should do when a Tornado Warning is issued for your area, 

Take immediate action, but remain calm. If you are at home or in
a small building, go to the basement or to an interior room on
the lowest floor. Closets, bathrooms, and other interior rooms
without windows offer the best protection. Avoid windows and get
under something sturdy or cover yourself with a mattress.

If you are in a school, hospital, or shopping center, go to a
pre-designated shelter area. Stay away from large open areas such
as gyms or auditoriums, hallways and small interior rooms offer
the best protection. Do not go outside to your car. If you are in
a high-rise building, go to an small interior room or hallway on
the lowest floor possible. Do not use the elevator.

Mobile homes are easily tossed about by the strong winds of a
tornado. Immediately take shelter in a substantial structure.

If you are caught outdoors and cannot get to a safe
building, as a last resort, you should:

If you have access to a vehicle, get in and buckle your seat belt 
and try to drive to the closest sturdy shelter. If your vehicle is 
hit by flying debris while you are driving, pull over and park. 
Stay in the car with the seat belt on. Put your head down below the
windows, cover your head with your hands and a blanket, coat or
other cushion if possible.

If you can safely get noticeably lower than the level of the
roadway, leave your car and lie in that low area, covering your
head with your hands.

Your choice of whether to stay in your car should be driven by your 
specific circumstances. If you are in a car or if you seek shelter 
in a depression or ditch with a tornado approaching, you remain at 
risk. The safest place to be is in an underground shelter, basement 
or safe interior room.

For additional information on tornadoes and severe weather check out 
our web site at:

weather.gov/statecollege

Our weather safety topics for the rest of the week will be, 
Tuesday, Thunderstorm Safety.
Wednesday, Flash Flood Safety. 
Thursday, River Flood Safety.
Friday, Skywarn Severe Weather Spotters.

Now is the time to prepare for this year's severe weather season.

 

Today's Topic: Severe Thunderstorms!

Tuesday's Activities:

Click any Topic to Expand or Contract

1. Learn about Thunderstorms.
2. What is a Severe Thunderstorm?
3. Review Safety Rules.
4. Have a Safety Plan!
Daily Safety Message:  
Our severe weather and weather safety topic for today is, 
"Severe thunderstorms."

We will cover what classifies a thunderstorm as severe, and what 
the differences are between a Severe Thunderstorm Watch and a Severe 
Thunderstorm Warning.  We will also give you information on what to 
do when a watch or warning is issued for your area.

What is a severe thunderstorm?

A thunderstorm is considered severe if it produces wind gusts 
of 58 miles an hour or higher, and/or hail one inch in 
diameter or larger. Those hailstones are about the size of a 
quarter. Severe thunderstorms are often accompanied by
torrential downpours and frequent lightning. They can also 
produce brief, weak tornadoes. The damage from the strong wind 
gusts of a severe thunderstorm can be just as bad as the damage 
made by a tornado. Severe thunderstorms are much more common than 
tornadoes. 

What is a Severe Thunderstorm Watch?

A Severe Thunderstorm Watch is issued in order to alert you that 
thunderstorms with damaging winds and large hail are expected to 
develop close to your location. A watch by itself does not mean 
that severe weather is actually occurring yet, it means that 
severe weather is expected to happen close by. A severe 
thunderstorm watch usually covers an area as large as a state, 
And is in effect for several hours, expiring only when the 
thunderstorms are expected to end.

What should you do when a Severe Thunderstorm Watch is issued?

Go about your normal activities, but watch the sky around you
for developing storms. Periodically check NOAA Weather Radio or
other media outlets for forecast updates and possible warnings. 
Know which county you live in, and which ones border your 
community. Think of a safe place to be and plan a route which 
you can use to get that safe place quickly. 

What is a Severe Thunderstorm Warning?

A Severe Thunderstorm Warning means a severe thunderstorm is 
occurring and is going to move through your location soon. It is 
your signal that you will need to take quick action to protect your 
life and property.  Severe Thunderstorm Warnings are issued by the 
National Weather Service when meteorologists detect a severe 
thunderstorm using Doppler radar or when damage has been reported by 
trained Skywarn weather spotters. 

Typically, a Severe Thunderstorm Warning will be issued for an area 
as big as a county or two, and for a period of up to one hour. In 
the text of the warning statement, we try to make a specific list 
of towns that are likely to be in the path of the storm. You should 
listen to hear if communities or landmarks near you are mentioned in 
the warning. 

What should you do when a Severe Thunderstorm Warning is issued for 
your location?

If you are outdoors, get inside your home, a strong building, 
or in your car. Boaters should head to shore immediately.

When indoors, go to an interior room on the lowest level. Stay away 
from windows and exterior doors. Do not use electrical appliances 
and avoid using the telephone, as lightning can travel through 
electrical and telephone lines. 

If you are driving, safely pull over to the side of the road until 
the storm passes. Heavy rain falling from any thunderstorm can flood 
roads quickly, so never try to drive through an area where water 
covers the road, even if you think it is shallow. Water may sweep 
your vehicle away if you attempt to drive through it.

For additional thunderstorm and severe weather safety information
check out our web page at:

weather.gov/statecollege.

Our weather safety topics for the rest of the week will be, 
Wednesday, Flash Flood Safety. 
Thursday, River Flood Safety.
Friday, Skywarn severe weather spotters.

 

Today's Topic: Flash Flooding!

Wednesday's Activities:

Click any Topic to Expand or Contract

1. What is Flash Flooding?
2. Where does Flash Flooding Strike?
3. How you can stay safe during Flooding. (Link)
4. Turn Around Don't Drown!Turn Around Don't Drown Logo (Link)
Daily Safety Message:  
Our severe weather and weather safety topic for today is, 
Flash flooding and flash flood safety. 

More people are killed by flash floods than by other storm-related 
weather hazards. Unfortunately, most people succumb to flooding 
after they drive their automobiles into flooded roadways and are 
subsequently swept away to their deaths. 

If you encounter a flooded roadway, Turn Around, Don't Drown!
Find another route, it could save your life! Many people lose 
their lives by not adhering to this simple rule, 
  Turn Around, Don't Drown!

What is a flash flood?

A flash flood is a rapid flood.
During a flash flood, a stream or creek will rise rapidly and 
crest generally within a few hours of the start of the heavy rain. 
Flash floods are so dangerous because the waters rise so 
quickly that they can catch people off guard and trap them in 
precarious situations. This is why the National Weather Service 
constantly monitors rainfall using rain gauges and radar 
estimates, as well as monitoring stream and creek levels  
using automated river gauges and local spotters. Your National 
Weather Service will issue Flash Flood Watches and Flash Flood 
Warnings to help alert you to expected flood dangers. 

What causes flash floods?

Flash floods are caused when very heavy rainfall, usually from
slow-moving thunderstorms, overwhelms the natural or man-made 
drainage systems. Streams, creeks and smaller rivers are most 
vulnerable to flash flooding. Flash flooding occurs in urban 
areas as well as in rural areas.

What does a Flash Flood Watch mean?

A Flash Flood Watch means that the potential exists for flash
flooding to occur on any stream, creek or small river. The watch
does not mean that flooding is imminent or occurring. It just means
that it is a possibility.

What you should do when a Flash Flood Watch is issued, 

Be prepared to take quick action to protect yourself by moving to
higher ground if you are near a waterway. Watch water levels
carefully and be ready to evacuate at any moment. If you are
traveling during a Flash Flood Watch, be alert for signs of flash
flooding, especially at night when it can be difficult to see a
flooded roadway. Be very careful if driving through flood prone
areas, and if you encounter a flooded roadway, 
  Turn Around, Don't Drown! 
Find an alternate route. It could save your life!

What does a Flash Flood Warning mean?

A Flash Flood Warning means rapid life-threatening flooding is 
occurring, or will begin very soon. A warning lets you know that 
heavy rain will cause the water to rise and overflow the banks of 
the waterways nearby. A Flash Flood Warning can also be prompted by 
levee and dam failures. You need to take action immediately to 
protect your life and property if you are in the danger area.

What should you do when a Flash Flood Warning is issued?

Move up to higher ground immediately and get out of the danger area.
Never drive across bridges covered with water, or through areas 
where water covers the roadway.  Most cars will float in just 16 to 
18 inches of water. If rising water captures your automobile, it 
could easily sweep you away. Be especially cautious at night, when 
it is harder to recognize that an area may be flooded.

For additional information on flash floods and severe weather, 
Check out the National Weather Service web site at:

weather.gov/statecollege.
 
Our weather safety topics for the rest of the week will be, 
Thursday, River Flooding Safety.
Friday, Skywarn Severe Weather Spotters.

 

 

Today's Topic: River Flooding!

Thursday's Activities:

Click any Topic to Expand or Contract

1. How common is River Flooding,
and when is it most likely to occur?
2. Where/How can I monitor the Flooding or the River Forecasts? (Link)
3. How you can stay safe during Flooding. (Link)
4. Turn Around Don't Drown!Turn Around Don't Drown Logo (Link)
Daily Safety Message:  
Our severe weather and weather safety topic for today is, 
"River Flooding and River Flood Safety." 

Pennsylvania has an extensive river system that is scenic and 
beautiful. Most of the towns and cities were founded on the banks of 
a river or large creek. This means that when river levels 
rise, many people will be affected at the same time. The rising 
river waters can become destructive, and even deadly. 
Significant, widespread river floods have occurred in Pennsylvania 
almost every year.

What causes river floods?

Generally, river floods happen due to prolonged periods of
widespread heavy rainfall. 

Our rivers can flood anytime of the year. In spring and 
summer, complexes of slow moving thunderstorms can cause the rivers 
to flood. During late summer and fall, heavy rain from tropical 
storms and hurricanes are the biggest cause of river flooding. 

Sometimes, an extensive snow melt occurs at the same time as heavy 
rain. This is especially true in late winter and early spring when 
the snow pack of the previous winter melts away. The destructive 
flooding of January 1996 was one such situation where snow melt and 
heavy rain combine to push river levels even higher. 

River flooding can result in widespread property damage and may 
result in loss of life. More than 50 percent of the deaths 
associated with flooding are automobile related.

What does a Flood Watch mean?

A Flood Watch means there is potential for flooding to occur, 
Not that river flooding is occurring. A Flood Watch is typically 
issued for an area many counties in size, and is usually issued 12 
to 24 hours before flooding is expected to start. With the advance 
notice of a watch, you will have more time to prepare for the 
flooding.

What you should do when a Flood Watch is issued?

Go about your normal activities, but make periodic checks of NOAA 
Weather Radio or other media outlets for updates and possible flood 
warnings. Listen for river level forecasts from the National Weather 
Service. Get ready to move your personal property out of the areas 
that are known to flood. If you live in the flood plain, be 
prepared to evacuate if ordered to do so. 

If you live or work in an area which is prone to flooding,  Have a 
safe evacuation route to use if flooding occurs. Make sure everyone 
in your home or office knows where to go if flooding occurs. Move up 
to higher ground to escape flood waters. Keep a battery operated 
radio, and several working flashlights available. Take precautions 
to secure your property.

What does a River Flood Warning mean?

A River Flood Warning means that river levels will exceed flood 
stage at certain points along our larger rivers, like the 
Susquehanna and Juniata rivers. 

Because river floods take longer to develop than flash flooding 
does, river floods may not pose as much of a threat to life, 
But, river floods can take a much larger toll on property and 
infrastructure.

What should you do when a River Flood Warning is issued?

Gather all necessary items, including medicine and clothing, in 
the event that you cannot return home for several days. Make 
arrangements to protect your property by moving your valuables to 
higher ground, or to an upper level of your home.

Obey evacuation orders from emergency management or local law 
enforcement officials, avoiding any roads that are or may be 
covered with water.

For additional information on river flooding and severe weather
check out our web site at:

weather.gov/statecollege. 

Our weather safety topic for Friday will be, 
Skywarn Severe Weather Spotters.

 

Today's Topic: Skywarn™ Spotters!

Friday's Activities:

Click any Topic to Expand or Contract

1. What is a Skywarn™ Spotter?
What do they do?
How do I become one? (Link)
2. See the NWS Basic Spotters Guide (Link to pdf file)
Daily Safety Message:  
Our final severe weather and weather safety topic for Severe Weather
Awareness Week is, "Skywarn Severe Weather Spotters."

Each year, a dedicated group of volunteer weather spotters, known 
as Skywarn, provide National Weather Service offices across the 
country with important, eyewitness, information about tornadoes, 
Flash floods and damaging thunderstorms.

Skywarn spotters are people with an interest in the weather, and 
an interest in helping others.

While Doppler weather radars can help meteorologists identify 
rotating thunderstorms, skywarn spotters can help to pinpoint 
places where a tornado may form, even before a tornado touches 
ground. Skywarn spotters are also essential to confirm that 
tornadoes have touched down, to report on the extent of 
damage, and to provide added details of a threat to a community.

A large number of Skywarn spotters are also ham radio operators. 
Amateur radio emergency groups and amateur radio clubs are called 
into action whenever Tornado or Severe Thunderstorm watches or 
warnings are in effect across the commonwealth.  These spotters 
collect information via ham radio nets, and then relay that 
information to emergency management and to the national weather 
service.

All the staff of your National Weather Service would like to thank 
our many friends in the skywarn program, thank you for your great 
help. Your volunteer efforts are very much appreciated.

Again, as a part of emergency preparedness, the Pennsylvania
Emergency Management Agency, county emergency managers, and those 
of us at the National Weather Service want you to know about the 
fine help that ham radio and other volunteer skywarn spotters 
provide to the commonwealth.

Be prepared for the dangers of this severe weather season, and 
consider becoming a Skywarn spotter.