Lake Affect Snow
And it’s

Effect on

Aviation
BY:
Perlisha Humphrey
And
Duane Johnson

Imagine driving on high way U. S. 2 in the Upper peninsula of Northern Michigan just outside of Marquette, on a sunny winter day as the skies turn dark and ominous clouds build in the distance. Suddenly, a “wall of white” appears several hundred yards ahead and some of the heaviest snow you have ever seen obscures everything in your path. You inch forward through the blizzard until you arrive on the other side – where skies once again turn sunny. Anyone who lives in the Great Lakes region is familiar with this unique type of winter weather. This heavily localized snowfall, known as lake-effect snow, is most common from November to February. The winter weather phenomenon is capable of whiting out large sections of the Great Lakes region, from South Bend, Indiana, to Buffalo, New York. Towns and cities at higher elevations can expect even larger amounts of lake-effect snow.
The Recipe for Lake-Effect Storms Lake-effect snow forms in the winter when cold air masses move over warmer lake waters. As the warm lake water heats the bottom layer of air, lake moisture evaporates into the cold air. Since warm air is lighter and less dense than cold air, it rises and begins to cool. The moisture that evaporates into the air condenses and forms clouds, and snow begins falling. This may seem like the recipe for whole world but due to the sheer size of the great lakes and the fact that it is fresh water and not salt, the amount of evaporation is much greater causing larger amounts of moisture in the air. Snow clouds most often form in narrow bands where the size and orientation are determined by the shape of the body of water and the prevailing wind direction. In the most extreme cases, the heaviest bands of snowfall may be 20 to 30 miles wide and extend over 100 miles inland from the lake. Within the band, snowfall rates may exceed 5 inches an hour and be accompanied by lightning and thunder, a phenomenon known as thunder snow. A band of snow can hover over one location for several hours, dropping several feet of snow; however, 10 to 15 miles on either side of that narrow band skies may be sunny with no snow at all.
Airport Consequences The operational consequences at an airport that is experiencing lake effect snow can be significant. Delays and de-icing are certainties and diversions are likely as normal airfield operations can be severely impaired. Operators should anticipate and plan for the following: De-icing. Due to the heavy snowfall, ground de-icing will be required, even during a quick-turn around. Aerodrome de-icing services might be overwhelmed, due to the high demand, resulting in departure delays. Contaminated Surfaces. Ramps, taxiways and runway surfaces are all likely to have some contamination present. Performance calculations for both takeoff and landing must consider the consequences of the runway contamination. Snow Clearing Operations. Simultaneous snow clearing and aircraft operations will be in progress which can result in delays. This also produces safety concerns with the constant clearing of snow and the landing and departure of aircraft. Longer Turn-around Times. Aircraft servicing operations such as towing, pushback, loading, refueling and water/lavatory servicing will all be impeded by the snow. Delays can be expected. Runway Closures. Temporary runway closures will be required for snow clearing. At airports with multiple runways, operations may be shifted back and forth between runways to facilitate snow clearing. Under extreme snowfall conditions, limitations in snow removal capacity may result in the loss of one or more runways and, ultimately, in the closure of the airport. Reduced Visibility. Visibility will be reduced in snow and blowing snow. Low Visibility Procedures may be in effect. Reduced Aerodrome Capacity. All of the previously mentioned factors can result in a capacity reduction for both inbound and outbound flights. Delays and Diversion Potential. Diversion potential is significant as any fuel beyond reserve fuel requirements may be exhausted due to arrival delays. Increased Fuel Requirements. Ground delays for departing aircraft and holding, approach and ground delays for arrivals will all contribute to an increase in fuel consumption. Many weather related factors play a part in an aircraft’s performance and in some cases an aircraft’s demise as well. Aircraft have weaknesses to the elements such as ice, frost, wind, and temperature changes. Aircraft can be flying along, and due to a change in the weather could be in danger of crashing to the ground. Frost or a thin coat of ice buildup on an aircraft’s wings can cause serious trouble when air flow is disrupted over aircraft surfaces. Aircraft icing can increase drag and reduce lift during takeoff, and can also lead to a sudden pitch or roll situation during flight. Ice accumulation inside engines is a source of foreign object damage or (FOD). Ice can cause problems with an aircraft’s instruments and how well they operate during flight. Temperature can affect altitude and airspeed readings causing inaccuracy during flight. Weather is continually changing, and can suddenly change without warning at times. In order for pilots to be aware of weather conditions before flying the Federal Aviation Administration developed a process to evaluate the weather conditions known as the 3-P model. The three P’s stand for perceive, process, and perform. Perceive what the weather hazards could be, process the possible hazards and the potential impact of a hazard, and perform actions to mitigate or eliminate the hazard of weather risks. Atmospheric turbulence takes place when cold and warm air mixes in the atmosphere. The wind is also dangerous weather for aircraft and passengers to encounter. Atmospheric weather at different altitudes is harder to predict than surface weather. Seth Gutman, an atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado is studying a new way to warn pilots of turbulence (Dorminey, 2014). By using the existing global positioning system to probe for atmospheric turbulence, one day a warning system could be in place to alert pilots to turbulence. Gutman explains that GPS signals are refracted and delayed by water vapor as the signals travel through earth’s lower atmosphere. “We take the signal delay info and put that into weather models, but instead of averaging this out over half an hour, we propose doing it over timescales of about a second at a time.” (Dorminey, 2014) Some air turbulence can be uncomfortable to make it through, but does not cause damage to the aircraft, but at other times air turbulence can be a nightmare. One example of severe air turbulence is when a DC 8 cargo plane in 1992, suffered severe air turbulence that took 12 feet of the left wing and the left outboard engine off the plane while flying over the Front Range of Colorado’s Rocky Mountains. Had there been some type of detection system in place this accident may not have happened. All in all, weather is the single most important uncontrollable factor in flight.

Bibliography
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Aviation Weather. (2014, March 1). Retrieved from www.faa.gov: faa.gov/pilots/safety/media/ga_weather_dec
Dorminey, B. (2014, February 28). Fighting Aviation Turbulence with High-End GPS. Retrieved from www.forbes.com: http://www.forbes.com
Godlewski, M. (2012, September 24). Cirrus compromised by turbulence. Retrieved from generalaviationnews.com: http://generalaviationnews.com/2012/09/24/cirrus-compromised-by-turbulence/
Warm Water and Cold Air. The Science Behind Lake-Effect Snow. (2005) NOAA http://www.noaa.gov/features/02_monitoring/lakesnow.html
Lake Effect Snow. Retrieved from http://aviationsafetywiki.org/index.php/Lake_Effect_Snow