National Weather Service United States Department of Commerce
The week of November 7th through November 11th, 2016 is
Winter Weather Awareness Week in Pennsylvania.

PEMA logo and link

FEMA logo and link

PENNDOT logo and link
How PENNDOT prepares for Winter Operations
PENN DOT's "Winter Storm Tactics" (pdf)
511pa.com = ROAD CONDITIONS

American Red Cross link and logo

Winter Weather Brochure (pdf)

 

PREPARE FOR WINTER STORMS

 

One of the key lessons from natural disasters over the last several years is that individuals must be prepared to deal with the effects of hazardous weather conditions. Today we explore steps you can take to mitigate against Pennsylvania’s sometimes harsh winter weather. 

Heavy snow can pile up several feet, delighting skiers, but clogging roads or trapping us in our homes. Freezing rain can rob us of electricity or turn our highways into deadly thoroughfares.  Biting cold and strong winds can make the spot by the fireplace seem cozy, but they also numb our fingers and toes, or even worse. These are all facts of life in our temperate climate during the winter. However, there is plenty we can do to help protect ourselves and our loved ones.

Winter is the most dangerous time of the year for drivers. Nearly three out of every four winter weather related deaths occur on our highways. When roads are snow covered or icy, slow down and drive very carefully.

The cold weather also puts an added strain on vehicles. We suggest, if you have not already done so, that you get your car in good mechanical working order now. Make sure it is tuned up. Check your tires, brakes, windshield wipers, and antifreeze. If your car is in good working order, there is less chance it will fail when you need it most.

Consider keeping a blanket or a sleeping bag in your car. Prepare a winter storm survival kit for your car. This kit should include a first aid kit, flashlight with fresh batteries, shovel, sack of sand or cat litter, booster cables, tow rope, ice scraper and brush, candy bars or other high energy non perishable food, and paper towels. You should keep your gas tank at least half full to avoid ice in the tank and fuel lines.

Call ahead to your destination to tell someone you are on your way. Try not to travel alone and use primary roads as often as possible. If you are stuck in your car during a winter storm, stay there, and tie a brightly colored cloth to the antenna. Do not attempt to walk to safety unless you can clearly see the shelter you wish to reach.

You are more likely to be rescued from your vehicle than from a barn or other uninhabited, out of the way building. While waiting for help run the vehicles engine and heater for several minutes every hour, just enough to keep from becoming unreasonably cold. Make sure to open a window slightly, and clear snow from the tailpipe. This will help prevent carbon monoxide poisoning from the exhaust.

Dress warmly for the cold weather. Several layers of loose fitting clothing are better than one tight fitting garment. Mittens are warmer than gloves. Do not forget your hat since the body's greatest heat loss occurs through your head. Wind chill, the combination of cold temperatures and wind, can be a real problem. A twenty mile an hour wind makes a bearable thirty degrees feel like a bitter 17 degrees. This can have an adverse effect on your body. The strong wind increases the danger of frostbite or hypothermia.

Be especially cautious when venturing out onto an ice covered body of water. An ice thickness of at least four inches is recommended to support a person. Snowmobiles and atvs need at least five inches of ice, while cars and light trucks require at least eight to 12 inches. Factors which can be used to assess the strength of the ice include the ice appearance, thickness, daily temperature, snow cover, and distribution of the load on the ice.

TERMS AND DEFINITIONS

 

Here are some terms which the national weather service uses to describe winter weather as well as the definitions of watches, warnings and advisories issued for winter weather events. A hazardous weather outlook is issued prior to a winter storm watch. The outlook is issued when forecasters believe winter storm conditions are possible. Outlooks are usually issued 3 to 5 days in advance of a winter storm.

In general a winter storm watch alerts the public to the possibility of heavy snow, heavy freezing rain, or heavy sleet. Winter storm watches are usually issued 24 to 72 hours before the beginning of a winter storm. These events may occur separately or in combination. A blizzard watch is issued when blizzard conditions are possible in 24 to 72 hours.

Since watches are issued well in advance of the storm, there will be times when the storm does not materialize, so they may be canceled.

On the other hand, a warning is issued when hazardous winter weather is imminent or has already begun. It is issued for conditions which pose a threat to life and property.

The following are the warning headlines issued for winter weather events...

  • A winter storm warning is issued when hazardous winter weather in the form of heavy snow, heavy freezing rain, heavy sleet or any combination of heavy winter precipitation, is imminent or occurring. Winter storm warnings are usually issued 12 to 24 hours before the event is expected to begin.
  • A blizzard warning is issued for sustained or gusty winds of 35 mph or more, and falling or blowing snow creating visibilities at or below one quarter mile. These conditions should persist for at least 3 hours.
  • An ice storm warning is issued when significant ice is expected to accumulate on trees, powerlines and roads. An ice storm is a very dangerous storm, disrupting traffic, and knocking down powerlines. Prolonged power outages can occur leaving people without power for up to a week or more.
  • A lake effect snow warning is issued when heavy lake effect snow is imminent or occurring. 
  • A wind chill warning is issued when wind chill temperatures are expected to be hazardous to life within several minutes of exposure, usually at temperatures below minus 25 degrees Fahrenheit.

An advisory is issued for less serious weather conditions. Specific advisories will alert you to weather that would have a significant effect on motorists, outdoor activities, or public events.

The following are the advisory headlines issued for winter weather events...

  • A winter weather advisory is issued for accumulations of snow, freezing rain, freezing drizzle, and sleet which will cause significant inconveniences, but if sufficient caution is exercised, do not usually threaten life and property.
  • A freezing rain advisory is issued for any accumulation of ice from freezing rain or freezing drizzle. It only takes a small amount of ice to make roads very treacherous.
  • A lake effect snow advisory is issued when accumulations of lake effect snow will cause significant inconvenience.
  • A wind chill advisory is issued when wind chill temperatures are expected to be a significant inconvenience to life with prolonged exposure, and, if caution is not exercised, could lead to hazardous exposure.

If you need timely information, you can get it on NOAA weather radio all hazards. We broadcast twenty four hours a day across all of Pennsylvania.

Weather radio monitors are inexpensive and guarantee you the latest weather whenever you have the need. Our broadcasts will help you plan for outdoor activities, get travel information, make business decisions, or decide on the proper clothing to wear. Most importantly, you will be ready when a winter storm strikes.

We issue frequent updates during active winter weather, that serve to give you the most up to the minute, and detailed weather information available. In addition, we issue statements that follow up on the issuance of watches, warnings, or advisories.

 

TYPES OF HEAVY SNOW EVENTS WHICH IMPACT PENNSYLVANIA

 

Heavy snow can immobilize a region and paralyze a city, stranding commuters, closing airports, stopping the flow of supplies, and disrupting emergency and medical services. Accumulations of snow can cause roofs to collapse and knock down trees and power lines. Homes and farms may be isolated for days and unprotected livestock may be lost. The cost of snow removal, repairing damages, and the loss of business can have severe economic impacts on cities and towns.

Heavy snow can be produced by nor’easters, blizzards and overrunning situations. Lesser amounts of snow are often produced by Alberta clippers.

  • Nor’easters are intense areas of low pressure that typically develop along the eastern seaboard most often during late fall, winter and early spring. They usually bring strong northeast winds to areas near the coast as they move north along it. Some memorable nor’easters in recent years included the President’s Day snowstorm of 2003, the February 11th and 12th storm of 2006, the Valentine’s Day snowstorm of 2007 and the snowstorm of February 25th and 26th, 2010. Snowfall rates in nor’easters can reach 2 to 4 inches per hour and these rates can last for several hours.
  • Overrunning can also produce heavy snow. This occurs when warm air aloft flows over cold air near the surface. Overrunning happens mostly during the winter when the contrast in airmasses is greatest. Overrunning occurs most often when a large dome of high pressure is located in southeastern Canada and a warm front is approaching our region from the south or southwest.
  • An Alberta clipper is an area of low pressure that usually develops over the province of Alberta in Canada, east of the Rocky Mountains. Alberta clippers usually move very quickly southeast from their point of origin and usually bring only light snow as they cross our region unless they intensify off the east coast. They also allow colder air from Canada to move into our region in their wake.

Some snow terms which are commonly used include blizzard, blowing snow, snow squalls, snow showers and snow flurries.

  • A blizzard is a winter storm which has sustained winds or frequent gusts of 35 mph or more, with considerable falling and or blowing snow frequently reducing the visibility to at or below one quarter mile, and these conditions last for 3 hours or more. Some of the greatest snowfalls on record in Pennsylvania occurred during blizzards. 1 to 2 feet of snow fell over a large part of Pennsylvania during the blizzard of 1993.
  • Blowing snow is wind driven snow that reduces visibility. Blowing snow may be falling snow or snow already on the ground that is picked up by the wind.
  • Snow squalls are brief intense snow showers accompanied by strong gusty winds which may produce significant snow accumulations.
  • Snow showers have snow falling at varying intensities for brief periods of time with some snow accumulation possible.
  • Snow flurries are light snow which falls with little or no snow accumulation.

 

ICE STORMS

 

Heavy accumulations of ice can bring down trees and powerlines, as well as topple utility poles and communication towers. Ice can disrupt communications and power for days while utility companies repair extensive damage. Even small accumulations of ice can be extremely dangerous to motorists and pedestrians. Bridges and overpasses are particularly dangerous because they freeze before other surfaces.

Freezing rain is the result of precipitation which initially falls as snow, then encounters a layer of warm air which melts the snow changing it to rain. The rain then freezes as it encounters below freezing air at or near the surface creating a film of ice.

Most of the United States receives less than 10 hours of freezing rain annually with the highest frequency in the Saint Lawrence River valley where over 40 hours of freezing rain are observed annually.

The national weather service issues ice storm warnings for Pennsylvania when significant ice accumulations are expected and winter weather or freezing rain advisories for any ice accretion which also includes freezing drizzle. The Poconos in northeast Pennsylvania are most susceptible to ice storms with the most recent storms occurring in January 2003 and 2005.

 

WINTER FLOODING

 

One of our deadliest winter weather hazards is flooding.

In Pennsylvania one usually associates snow, ice, and biting cold with winter. But sometimes nature throws a curve at us with unseasonable warmth, and with it, rain.

A number of different factors work together to produce floods in winter.

When unseasonable warmth comes to the region it will often melt much, if not all of the snow on the ground in the lower elevations. The melting snow will saturate the ground and also begin to swell the rivers.

Often the warmer air will rise over colder air trapped in the region. As this air rises it results in clouds and rain, which will combine with the melting snow to increase flows in the rivers. When this melting snow combines with heavy rains it can put enough water into the rivers to send them over their banks.

Some of our worst winter floods are caused by intense cyclones that track from the Ohio valley northeast up the Saint Lawrence Valley into Canada. These storms bring a lot of warm and moist air into the region from the Gulf of Mexico and the Atlantic, bringing both mild temperatures and heavy rain to the region.

In January 1996, unseasonably warm air and heavy rain combined to melt a deep snowpack in Pennsylvania. The combination of melting snow and heavy rain led to the worst flooding in Pennsylvania since hurricane Agnes in 1972.

Another winter problem is flooding caused by ice jams on the rivers. As river flows increase, water levels rise. Since ice that covers the rivers is lighter than water it will tend to float. Under the pressure it will often break into huge slabs. These slabs will then move downstream in the current until they run into an obstruction such as a bend, island, or wide shallow area. When this happens the ice will often stop and pile up into a jam. When the flow of the river is blocked by an ice jam, the water can overflow the river banks in less than an hour as it tries to get around the ice. As the water rises, the pressure can break the jam and release a sudden surge of water and ice down the river.

While ice jams often form in the same spots year after year it is nearly impossible to predict exactly when or where a jam will form, or when one will break. Sometimes a jam that forms in early winter will stay put most of the winter.

Severe flooding of roads and built up areas can also occur when mounds of plowed snow and ice block and plug up the grates and storm drains, so the water from the pavement has nowhere to go. This standing water can cause dangerous black ice if it freezes.

FROSTBITE AND HYPOTHERMIA

 

Very cold weather can be a health hazard. However by dressing properly, you can safely spend time outdoors enjoying what the area has to offer in the form of winter recreation, whether it be skiing, snowmobiling, ice skating, or just taking in the winter scenery.

Very cold temperatures can rob your body of life sustaining warmth, especially when combined with a strong wind. The combination of cold temperatures and wind is known as the wind chill. The wind chill is based on the rate of heat loss from exposed skin. As the wind speed increases, the rate of heat loss from your body also increases. A temperature of 20 degrees above zero with a wind can feel like a bitter cold 6 degrees when the wind blows at 15 miles an hour.

Frostbite can occur when your fingers, cheeks, ears, toes, or even the tip of your nose is exposed to sub-freezing temperatures for a prolonged period of time. If any portion of your body becomes numb due to the cold, go indoors immediately and slowly warm the affected area to avoid tissue or nerve damage.

Hypothermia is potentially even more dangerous. This health hazard is defined as the lowering of the body temperature below 95 degrees. Warning signs of hypothermia include uncontrollable shivering, memory loss, slurred speech, and disorientation. If not treated immediately by keeping the person warm and seeking medical help, hypothermia can be fatal.

Hypothermia can affect anyone, but the elderly are the most susceptible. Over half the fatalities due to exposure from the cold occur to people over 60 years of age. Young children are also susceptible.

Be sure to dress properly for the cold. Always wear several layers of warm, loose fitting clothing. These layers help to retain your body heat better than one heavy layer, and they can be removed to avoid perspiration and subsequent chill. The outer layer of clothes should also be water repellent.

Don't forget to wear a hat since a significant loss of body heat occurs through your head. Also, mittens are better than gloves at protecting your fingers from the extreme cold.