National Weather Service United States Department of Commerce

 

December 4-10, 2022 is Winter Weather Awareness Week in Kentucky. The winter season can bring many different hazards and impacts to the region. Winter Weather Awareness week is your reminder that you need to be Weather Ready for all types of hazards, such as winter storms, snow squalls, ice storms, heavy rain and flooding, high winds, and even severe weather. All week long, the National Weather Service office in Louisville, KY will be sharing information on how to prepare for winter, which will be viewable on our social media platforms (Facebook and Twitter). Please Share/Retweet to share this knowledge with others.

 

Winter Weather Headlines Issued by NWS Louisville

Winter Weather Advisory:   For snow averaging between 1 inch and 4 inches within 12 hours, or a combination of impactful snow, sleet, or freezing rain within 12 hours and expected to occur in the next 2 to 3 days.

Winter Storm Watch: Any combination of snow, sleet, or freezing rain averaging 4 inches or more within 12 hours and expected to occur in the next 2 to 3 days.

Winter Storm WarningAny combination of snow, sleet, or freezing rain averaging 4 inches or more within 12 hours and expected to occur in the next 24 to 48 hours.

Ice Storm WarningA freezing rain event is expected in the next 24 to 48 hours that will produce ice accumulations of 1/4 of an inch or more.

Blizzard WarningA combination of sustained winds or frequent wind gusts of at least 35 mph and visibilities of less than 1/4 of a mile due to snow and/or blowing snow for at least three straight hours. This is expected to occur in the next 24 to 48 hours. 

Snow Squall WarningIntense bursts of snow with gusty winds causing whiteout conditions.

Wind Chill WatchWind chill values are expected to fall to -25 degrees F or less with at least a 10 mph wind in the next two to three days.

Wind Chill AdvisoryWind chill values are expected to fall to between -10 degrees F and -24 degrees F with at least a 10 mph wind in the next 24 to 36 hours.

Wind Chill WarningWind chill values are expected to fall to -25 degrees F or less with at least a 10 mph wind in the next 24 to 48 hours.

 

 

Know Before You Go! 

Don't let impactful weather sneak up on you. Check the latest NWS forecast for your zip code at weather.gov before you head out the door each day. Get the information you need, either in the detailed forecast that outlines the next several days, or in the hour-by-hour forecast if you need finer detailed weather information.

 

 

Winter Driving

 

Winter weather brings many impacts to our roadways each year, often resulting in many vehicle accidents, injuries, and fatalities. The information provided here is to help prepare you and your loved ones for the road ahead during the winter season. 

 

According to the United States Federal Highway Administration, 29% of weather-related crashes, and 20% of weather-related fatalities occur on roads covered with snow, slush, or ice. Each year, over 1,300 people are killed, and more than 116,800 people are injured in vehicle accidents that occur on now, slush, or ice covered roads. 

Each year, 15% of vehicle accidents occur during snowfall or sleet. During these accidents, nearly 900 people are killed, and nearly 76,000 people are injured. 

Winter weather caused major increases to road maintenance costs. The Federal Highway Administration states that winter road maintenance accounts for roughly 20% of state DOT maintenance budgets. Both state and local agencies can spend more than $2.3 billion per year on snow and ice control operations. When snow plows are out clearing our roads, be sure to leave them plenty of space! 

 

According to Tobin et all. 2022, approximately two-thirds (67%) of winter-weather-related fatalities occur on highways. The odds of a fatal crash occurring on a highway during winter-weather conditions is statistically significantly greater than those during nonadverse conditions.

 

Furthermore, nearly one-half (49%) of all winter-weather-related fatalities across the CONUS involve only a single vehicle. A slightly smaller fraction of fatalities (44%) involves two vehicles, and <8% of fatalities involve three or more vehicles.

 

More than one-half (56%) of winter-weather-related fatalities involve speeding, meaning that at least one driver involved in the crash was driving above the posted speed limit, or driving too fast for conditions, as indicated by law enforcement (NHTSA 2022).

 

The statistics above are enough to conclude that winter driving is hazardous. Slow down to keep yourself and everyone on the road safe. Remember, “Ice and snow, take it slow”.

 

 

    

 

    

 

    

 

    

 

 

 

Winter Storms

 

Power outages are common after a big winter storm. If you lose power, make sure to be careful when using alternative heat sources and practice portable generator safety. Once you and your family are safe, check in with others in your neighborhood to make sure they are okay.

 

As winter approaches, there are steps you can take to prepare your home for the cold weather ahead.

 

When the power goes out in winter, the cold can be deadly--but even without power, there are still ways to warm things up. Closing blinds and curtains and closing room doors can help contain heat, and stuffing towels in the cracks under doors can help keep the warmth in. Don’t forget about eating and staying hydrated - food provides energy to warm the body.

 

 

    

 

    

 

  

 

Did you know that a one or two degree temperature difference can play an important role in whether we get rain, sleet, or snow?

 

We work hard to provide you with the most accurate forecasts possible, and our forecasts get more precise the closer we get to a big weather event.

 

Winds

 

Strong storms with whipping winds commonly impact the U.S. during the cooler months. Each year, there are reports of trees and powerlines that have been knocked over and homes that have been damaged. Trim trees and shrubs and repair loose siding or shutters around your home well in advance of a storm. This can help reduce damage to your home. 

 

 

High winds can make driving dangerous. If driving during windy conditions, slow down and keep two hands on the wheel, avoid large trucks and trailers, and watch for downed tree branches, trees and power lines. Bridges and overpasses can be particularly dangerous to drive over when it is extremely windy, so choose routes to avoid them.

 

 

With little wind, your body is able to maintain a thin layer of warmer air between your skin and colder air surrounding you. However, higher winds can eliminate that thin layer, and your body can begin to cool at a dangerously fast rate.

 

Infographic - The Science of Wind Chill. The average temperature of the human body is 98.6 degrees fahrenheit. Under calm conditions, the body radiates heat, creating a layer of warmth between or skin and the cold surroundings.  But when it's windy, the moving air breaks up this insulating layer. It speeds up heat loss by whisking away the warmth from our skin. Hypothermia begins when our body temperature drops two to four degrees.

 

Even the most common items become dangerous objects when picked up and carried by the wind! When a High Wind Watch or a Severe Thunderstorm Watch is issued, secure outdoor items such as patio furniture, sports equipment and trash cans.  Recreational vehicles and trailers/campers are NOT a safe shelter from strong winds. Wind gusts can turn them over whether parker or in motion. If high winds are forecast, consider rescheduling your trip. If caught on the road during straight line winds, slow down and keep two hands on the wheel. Wind can be dangerous for those out on the water as well, because strong winds create large waves and can damage your boat, push you off course, or even cause you to capsize. If high winds are forecast, stay off the water and stow your vessel before conditions become hazardous. 

During high winds, falling trees and broken branches can become dangerous objects. Stay safe by avoiding exterior rooms and windows and by using caution when driving. Prevent damage to your property by trimming loose branches and parking away from trees. During strong thunderstorms, straight line wind speeds can exceed 100 mph and can cause damage similar to a tornado, knocking over semi-trucks, trees, and powerlines. Stay indoors and away from windows. Powerful storms can pack a windy punch. Don’t wait until you’re in the dark! Check your emergency kit now to ensure you have plenty of batteries and other essential supplies on hand.

 

Store or secure loose items before strong winds: patio furniture, trash cans, sports equipment, trampolines. RVs are at risk from strong winds. RVs and trailers/campers are not a safe shetler from strong winds. Wind gusts can turn them over whether parked or in motion. Check the forecast before you go, and have a way to receive weather warnings. Navigating Strong Wind. Dangerous wind can arrive well before (or without) rain. Reduce speed and head to shore if alerted to high wind. Always wear a life jacket. 

During high winds tree damage is expected. Stay safe by avoiding exterior rooms and vehicles while the winds are strong. Straight Line Winds. Straight line winds can exceed 100 mph, and affect large areas. Strong winds can knock over semi-trucks, trees and powerlines. Stay indoors away from windows. Avoid trees, power lines, and objects that could blow around. If driving, slow down and keep two hands on the wheel. Be prepared for power outages. Strong winds can knock out power. Check your emergency kit to make sure it has everything you need.

 

 

Floods

 

What does being Weather-Ready look like? When it comes to flood safety, it means knowing to never drive around barricades or through flooded roads, which are the cause of most flood fatalities.

 

What does Weather-Ready look like? During floods: Motorists who never drive around barricades or through flooded roads.

 

During a flood, water levels and the rate at which the water is flowing can quickly change. Get to higher ground. Do not drive or walk into water. It only takes 6 inches of water to knock you off your feet. Stay informed by monitoring local radio and television for updates.

 

3 Steps for Flash Floods: 1. Get to higher ground (get out of the areas subject to flooding).  2. Do not drive into water (do NOT drive or walk into flooded areas.  It only takes 6 inches of water to knock you off your feet). 3. Stay informed: Monitor local radar, television, weather radio, internet or social media for updates.  During a flood, water levels and the rate at which the water is flowing can quickly change.  Remain aware and monitor local radio and television.  WHEN FLOODED TURN AROUND DON'T DROWN

 

Most flood fatalities occur in vehicles, and it only takes 12 inches of water to sweep a car away. Sometimes, the difference between life and death is small decisions. During a flood, small decisions like turning around and not driving through a flooded roadway, not driving around barricades, and delaying travel until conditions improve, can make a big impact on whether you keep your car...or even your life. Turn Around, Don’t Drown.

 

Small Decisions can have a big impact: Flooding. 1) Turn around and don't drive through a flooded roadway. 2) Don't drive around barricades. 3) Delay travel until conditions improve. Don't let a bad decision be your last.

 

Flood events can devastate communities. Help yours be prepared and safe. A Flood WATCH means Be Prepared. A Flood WARNING means Take Action! Connect with your neighbors and discuss local flood risks and planning needs. If flooding is expected, help others elevate and protect their belongings. After the storm, check on your neighbors and keep others out of floodwater. Make sure to enable Wireless Emergency Alerts on your phone. If flooding occurs while you’re outdoors, immediately get to higher ground, and NEVER enter flood waters in a vehicle or on foot.  During a flood, water levels and the rate at which water is flowing can quickly change. You are safest staying indoors, or seeking higher ground if shelter isn’t available. If you’re stuck outside when a flash flood occurs, do not attempt to cross flood waters by vehicle or on foot.

Don’t underestimate the power of water. It only takes 6 inches of fast-moving water to knock over and carry away an adult, 12 inches to carry away a small car, and 18 inches of water to sweep a larger vehicle away.  It is impossible to know how deep the water is just by looking at it. More than 50% of all flood fatalities are vehicle related. NEVER drive around barricades into floodwaters!  You never know if the road is even below that muddy water anymore. When you drive into floodwaters, you’re not only putting your own life at risk, but also the lives of your rescuers. It’s far better to be late and remain safe than to take a risk and possibly lose your life.  Turn around, don't drown!

 

 Helping Others: Flooding. Connect with your neighbors about local flood risks and planning needs. If flooding is expected, help others elevate and protect their belongings. After storms, check on neighbors and keep others out of floodwater. Watch out for ice jams! Ice jams are accumulations of ice in a stream that obstruct flow. Once formed, water can rise several feet in a matter of minutes. Never attempt to cross flooded roads or drive around barricades. Flash flooding can escalate quickly. Heavy rain can lead to sudden flash floods, whether you're on the road or at a campground. Will you be ready? Set up a way to get weather warnings on your phone. When alerted to a flash flood, get to higher ground immediately. Never enter flood waters in a vehicle or on foot.

Flood Watch means be prepared. A Flood Watch is issued when flooding is possible. Stay tuned to trusted news sources and be ready to seek higher ground. Flood Warning means take action! A Flood Warning is issued when flooding is happening or about to happen. Move to higher ground immediately! Never drive or walk through flood waters. Your safe place from flooding: during a flood, water levels and flow speed can quickly change. You are safest by staying indoors, or seeking higher ground if shelter isn't available. If you're stuck outside when a flash flood occurs, do not attempt to cross flood waters by vehicle or on foot. I was driving a half-ton 4x4 which provides some comfort about not getting stuck in the mud. As I drove down the dirt road, I came across a low-water cement bridge. The bridge was completely covered in water, but not deep. I made a critical decision to turn around and drive the long way around to another highway. The next morning the water had receded and there was a huge hole — the water had washed away the dirt where the road met the cement. I would have surely lost the vehicle and maybe our lives…just saying “Turn Around and Don’t Drown” saved life and property. -- Julie, Nashville, TN, 2018 Play in the Pool, Not in Floodwaters!  Floodwaters can contain chemicals, sewage, and disease.  Unseen underwater debris can be sharp and cause injury.  Water depth can change unexpectedly (storm drains, washed-out roads) Don't underestimate the power of water! 6 inches of fast-moving water can knock over and carry away an adult. 12 inches of fast-moving water can carry away a small car. 18-24 inches of fast-moving water can carry away most large SUVs, vans and trucks. Do you really know how deep the water is?  6 inches of fast-moving water can knock over and carry away an adult.  12 inches of fast-moving water can carry away a small car.  18-24 inches of fast-moving water can carry away most large SUVs, vans and trucks. Never Drive Around Barricades.  Most flood fatalities occur in vehicles.  12 inches of fast-moving water can sweep a car off the road.     Driving into flood waters also puts rescuers' lives at risk.  Turn Around Don't Drown.

 

Fog

 

Fog, particularly when dense, can be hazardous to drivers, mariners and aviators. Fog contributes to numerous travel accidents every year. Restrictions in visibility resulting from fog can also impact takeoff and landing procedures and requirements for pilots, and can be the cause of weather-related aviation delays. 

 

 

If you find driving in foggy conditions, keep the following safety tips in mind:

  • Slow down and allow extra time to reach your destination.
  • Make your vehicle visible to others both ahead of you and behind you by using your low-beam headlights since this means your taillights will also be on. Use fog lights if you have them.
  • Never use your high-beam lights. Using high beam lights causes glare, making it more difficult for you to see what’s ahead of you on the road.
  • Leave plenty of distance between you and the vehicle in front of you to account for sudden stops or changes in the traffic pattern.
  • To ensure you are staying in the proper lane, follow the lines on the road with your eyes.
  • In extremely dense fog where visibility is near zero, the best course of action is to first turn on your hazard lights, then simply pull into a safe location such as a parking lot of a local business and stop.

 

Fog Safety - Disabled Vehicle in Dense Fog: 1. Pull well onto the shoulder. 2. Turn off all lights except 'flashers'. 3. If possible leave your vehicle and move away from the road. Patchy fog can surprise you: Be ready for sudden changes in visibility. Turn on your low-beam headlights when approaching fog. Drive slowly, and keep your distance from other vehicles. Use extra caution on bridges and in valleys. Dense fog is a road hazard: Turn on your low-beam headlights when approaching fog. Drive slowly, and keep your distance from other vehicles. Consider delaying travel when a Dense Fog Advisory is issued.

Ever wonder what causes fog? Fog forms when water vapor condenses into tiny drops near the ground. The three main types of fog are radiation, advection, and evaporation. Dense Fog Advisory mean dense fog is expected! Exercise caution. Areas of dense fog will reduce visibility and pose a threat to motorists. Allow extra time for travel, drive slowly, and use your low-beam lights.  

 

 

Science

 

Forecasting winter weather is one of the biggest challenges for meteorologist. A one degree change in temperature in the atmosphere and at the surface can mean the difference between you experiencing rain, snow, ice or a mix of all three. It is important for meteorologists to understand how these subtle changes can quickly change a weather forecast. 

 

Winter Precipitation: Below 32°F, snowflakes never melt. With sleet, droplets freeze and form ice before reaching the surface. Freezing rain is caused by rain, above 32°F in the sky, freezing on contact with the cold surface. If the surface temperature is above 32°F, rain will not freeze.

 

 

 

What Causes Winter? In the northern hemisphere, winter actually occurs when the Earth is closest to the Sun. This is because the northern hemisphere is tilting on its axis away from the Sun.  Science of River Flooding - Water is essential for life on Earth. But in large enough quantities, the very substance we drink and use to grow crops can destroy homes, businesses and cause fatalities. River flooding occurs when river levels rise & overflow their banks or the edges of their main channel and inundate normally dry areas. River flooding can be caused by heavy rainfall, dam failures, rapid snowmelt and ice jams. Six Steps to Create a River Model: Hydrologic Cycle: Hydrologists try to understand and simulate the natural hydrologic cycle, which is the intricate combination of many processes such as evaporation, transpiration, precipitation, infiltration, interflow, groundwater storage, and runoff. Precipitation: Precipitation is the primary input to basin hydrologic processes and serves as the primary driver of hydrologic models. Accurate representation of precipitation input is an important intial step. Small river channel systems are very sensitive to rainfall. Runoff: The next step is to compute the amount of precipitation that appears in surface water within a relatively short time from the onset of a storm event. This is runoff. Runoff consists of 3 components: overland flow, rain falling directly on surface water bodies, and interflow. Unit Hydrograph: After computing basin runoff, the next step is to calculate a forecast hydrograph in units of discharge. A hydrograph is a plot of the change of stage or discharge with respect to time. Discharge is the volume of water flowing past a location per unit time and is usually expressed in cubic feet per second (cfs). Streamflow Data: Scientists use streamflow measurements to capture the vital relationship between discharge (volume flow rate) and stage (height) for a given location. This can only be done by taking streamflow measurements at different river levels and noting the corresponding stages. This relation is called a rating curve. Routing: Hydrologists analyze and interpret how the water moves once it’s in the river and how a flood wave is modified due to the effects of storage and friction as it moves downstream. So, what happens upstream affects the entire downstream community.  Science of Snowflakes: No two snowflakes are the same, but they are all six-sided. Their shapes are due to the molecular structure of ice.

 

  Snow Water Cycle: The hydrologic cycle involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground to the atmosphere and back again. During the winter months, falling snow serves as an important source of fresh water across the world. When spring arrives, melting snow helps replenish rivers, lakes and reservoirs. The melting snow adds much needed moisture to the soil and helps refill underground aquifers, which are vital for growing crops and for drinking water.  Radiational cooling  is cooling of Earth's surface. At night, Earth suffers a net heat loss to space due to its cooling. More pronounced when you have clear skies, & even more pronounced when a particular location has three key ingredients: clear skies, calm winds, & snow cover.

 

 

 

Severe Weather 

 

Severe weather can happen during any month of the year across the Ohio Valley. Just because it is the winter season does not mean we do not get severe weather. Thunderstorms and squall lines can quickly turn clear skies dark. Stay Weather-Ready by having a way to get weather alerts on your phone, and stay safe by immediately going inside when the skies turn threatening. Visit weather.gov/safety/thunderstorm to learn more. 

 

 

No matter the season, Wireless Emergency Alerts can save your life from severe weather. WEA are emergency messages sent by authorized government alerting authorities through your mobile carrier. America’s wireless industry is helping to build a Weather-Ready Nation through this nationwide text emergency alert system. weather.gov/wrn/wea

 

Did you know that the tornado sirens are only meant for outdoor warning purposes? They are not meant to be heard indoors! County warning sirens are operated by you local city or county officials, and NOT the National Weather Service! 

 

  

 

    

 

    

 

If there is severe weather, we need your reports! Here's how you can send us reports.

 

 

 

How You Can Help Your Community

 

 

 

Accurate snow measurements are very important but taking those measurements can be difficult at times. The National Weather Service rely heavily on volunteers and the general public to provide snowfall measurements during winter weather events. We ask that you follow the procedures below as closely as possible when measuring snowfall and then forward the report on to us.

 

Do you know what to watch for when severe weather threatens? Check out NWS Skywarn. Help keep your community safe by volunteering to become a trained storm spotter for NOAA's National Weather Service. Potential volunteers should visit weather.gov/skywarn and contact their local NWS office. 

 

 

Check out the mPING (Meteorological Phenomena Identification Near the Ground) project. Weird name, cool app! You can report the type of precipitation you see where you are. No need to measure! Use the free mobile app to send reports anonymously. Reports are automatically recorded into a database, which improves weather computer models. The information is even used by road maintenance operations and the aviation industry to diagnose areas of icing. mping.nssl.noaa.gov

 

 

The NWS Cooperative Observer Program (COOP) is truly the nation's weather and climate observing network of, by, and for the people. With over 8,700 volunteer observers, this program has existed since 1890 and is one of the few programs that measures snowfall and its water equivalent. Help #NWSCitizenScience and become a COOP! You can help support warnings and forecasts, and contribute to building a climatological database! For more information, visit weather.gov/coop/Overview
 

 

Ever wanted to take rain or snow measurements? Join CoCoRaHS or the Community Collaborative Rain, Hail, and Snow Network. This volunteer network of observers measures precipitation from their backyards. Any age can volunteer. Data is used by NWS meteorologists to help with forecasts. www.cocorahs.org
 

 

 

 

Deaf and Hard of Hearing

 

Winter storms can be just as hazardous as any other type of weather, and it's important to be prepared. Learn how to prepare NOW with this video in American Sign Language.

 

Having a plan is important in times of emergency, and this includes building an emergency preparedness kit before a disaster. Learn how with this video in American Sign Language.

 

With our region experiencing moderate to severe drought, burning can quickly get out of control. Wildfires quickly consume everything in their paths. Learn how to prepare NOW with this video in American Sign Language.  

 

Severe weather can occur anytime of the year across our region. Just because it is winter does not mean you should not forget basic thunderstorm safety. This PSA for the deaf & hard of hearing community covers the basics of severe thunderstorm safety, explains Watches & Warnings, and touches on the various hazards that thunderstorms can bring.

 

 

 

 

 



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