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Snow Questions Answered

How do you forecast lake effect snow?

When arctic air moves into Western New York, 13WHAM meteorologists will be looking for certain criteria for lake snows to develop.

First, the surface temperature must be cold enough for the snow not to melt. Secondly, temperatures at approximately 5000 ft in altitude must be about 15 degrees Celsius colder than the lake water temperature. The lake water warms the cold air at the surface and it begins to rise. This creates what we call lake induced instability. We also need winds to be blowing at the nearly same direction through this layer. If they are not, the intensity of the snowfall can be drastically reduced.

If all these are present, we most likely include lake snow in our forecasts. The real forecast difficulty lies in determining exactly where and to some extent and how much snow will fall.

Ever heard of thundersnow?

Contrary to popular belief, thunder and lightning are not just reserved for the warm season.  In some cases, thunderstorms can form where snow falls.  This is called thundersnow, and although rare, it does occur.

These storms are not common due to the fact that thunderstorms need plenty of moisture and instability (vertical motion), which the cold winter air usually does not often contain. Arctic air masses are not capable of holding much water, and their dense qualities make high levels of instability hard to achieve.

However, in lake effect snow after a strong winter cold front passes, mild air over the lake can be lifted fast enough for the development of thunderstorm activity.  This often occurs in late Autumn when arctic air begins to flood the region, and the lake waters are still relatively warm.

Lake effect does not include just snowfall

The lake also has a significant affect on our weather during the late spring and summer, in addition to the lake effect snow that we experience during the winter.

The heat retention of the water in Lake Ontario helps to cause lake effect snow, by creating instability when colder air crosses its surface.  Conversely in the late spring, the cooler water causes a placating effect on the air above it, making it more difficult for clouds to form, sometimes even inhibiting their formation.

This can be called a lake shadow or Oasis Effect and is visible from satellite images downwind from many of the Great Lakes in the late Spring.

What community gets the most snowfall in New York State?

As you may know, the Tug Hill plateau is an area known for its high annual snowfall totals.  In fact, the plateau is the snowiest area east of the Rockies, and 300 inches of snow in a winter is not uncommon there. (Rochesters average is 95 inches.)

The high snowfall totals are due to a unique combination of topographic features, as the plateau sits at an elevation of about 2,000 feet above warm Lake Ontario.  Warm, moist air that crosses the lake is then forced to rapidly lift when it collides with the plateau, causing the air to rapidly cool and lose its moisture.  This can lead to extreme amounts of snowfall.

So the next time you have to shovel out your driveway around the Rochester area, realize it could be much worse.

How can wind impact lake effect snow?

In many cases, lake effect snow develops between altitudes of 5,000 to 10,000 feet. At times, surface winds can differ from winds at these altitudes substantially. In meteorology we call this wind shear.

If winds are from the northwest between 5,000 and 10,000 feet, and surface winds are from the west, then lake effect snow could drop down from the lake into lake shore communities. For ideal lake effect snow conditions, winds must be in fairly good alignment from the ground up to 10,000 feet.

When the wind direction varies at different levels of the lower atmosphere, lake effect snow becomes more disorganized. Some of the most memorable lake snow events occur east of Lake Ontario when surface winds line up with upper level winds on a westerly flow across the Lake.

What is Finger Lake snow?

Weve all experienced lake effect snow from the Great Lakes, but did you know that the Finger Lakes can also produce lake effect snow? 

With a wind out of just the right direction, areas such as Watkins Glen and Ithaca can experience snow from Seneca and Cayuga Lakes.  Since Seneca Lake is aligned generally north-to-south, a northerly breeze can generate a band of lake effect snow into Watkins Glen.  Since Cayuga Lake has more of a northwest-to-southeast orientation of its southern half, a northwesterly breeze can cause a band of snow into Ithaca.

Generally, its much more unusual to see a band of lake effect snow off the minor Finger Lakes, since the fetch, or distance the air has to interact with the water, is much shorter.  The minor lakes generally freeze much more readily, which causes lake effect snow to not be able to form at all.

What determines if it’s light, fluffy snow or heavy, wet snow?

Snowfall accumulation can be increased when significantly colder air is present. One of the basic principles of the atmosphere states that, The atmospheres ability to hold moisture is directly related to the air temperature at any given time. A warm atmosphere can hold tremendous amounts of water vapor while a cold atmosphere has a very limited ability to hold moisture.

Heres an example: If the air temperature is 30 degrees and the area receives 0.50 of liquid precipitation. This would equate to roughly 5 of snow. That same amount of liquid at 10 degrees would equate to 15 of snow. The fluffy snow at 10 degrees is also much easier to shovel and plow compared to the "slushier" snow around 30 degrees.

The Friday the 13th snow storm

Needless to say, lake effect snow is an incredible weather phenomenon. Early season lake effect snow is not uncommon in October. Typically warm lake waters between 50-60 degrees will produce lake effect rain rather than snow this time of year.

However, a bitter cold Arctic flow ushered in air that is more typical for late November or early December. This generated tremendous amounts of vertical lift and instability over lakes Erie and Ontario. Lake effect snow developed in the bitterly cold southwest flow. Due to a persistent southwest flow Buffalo received heavy snow and thunder snow from Lake Erie.

Estimates ranged from 10-30 in a 25 mile stretch from Orchard Park to Niagara Falls. Area trees still had leaves in these areas. This heavy, sloppy snow had extremely high water content (estimates of 2-3 liquid). This storm will forever be remembered as The Friday the thirteenth Snow Storm in Buffalo, or 'Arborgedden'.

What and where are the “snow belts”?

Portions of Western and Central New York are commonly referred to as Snow Belt regions of the Northeast.  We often live up to this name with our frequent bouts of lake effect snow which increases the average annual total to 100.3 for Rochester.

Of the 15 snowiest cities in the United States, four cities are located in New York State.  Syracuse is listed as fourth overall, Buffalo eleventh, Rochester twelfth, and Binghamton fifteenth.

The snowiest city in the U.S. is Blue Canyon, California with an average annual snowfall of 240.3 (20 feet).  The current United States record for greatest annual snowfall belongs to the ski area in Mount Baker, Washington, where they received an unbelievable 1140 (95 feet) of snow in 1998.

How intense was the blizzard of 1993?

On March 13 and 14 of 1993 a major winter storm moved along the East Coast. The combination of snow from the storm and lake effect snow that followed accumulated just under two feet officially in Rochester. Totals to the west were less with just over 17 inches falling in Buffalo. However, even higher accumulations were found to the east where in Syracuse 42 inches piled up.

The combination of heavy snow and wind gusts to nearly 60 mph caused extensive blowing and drifting and zero visibility at times. These conditions caused the New York State Thruway to be closed from Buffalo east. The snow finally came to an end early on March 15.

Why does snow crunch when it gets stepped on?

As you know snow is made of ice crystals and each ice crystal can contain up to six points.  Many snowflakes are comprised of multiple ice crystals.  In between each one of those ice crystals is a pocket of air.  When you step on snow you are compressing it below your feet.  As the snow is compressed that layer of air in between the crystals is forced out and we hear the sound of the ice crystals breaking.

Another ingredient for squeaky snow is cold temperatures.  Snow contains less moisture when the air is cold, thus allowing for more air to get trapped between each ice crystal.  Even though temperature is a factor, it is the structure of the snow that plays the largest role when it comes to crunch time.

What is the difference between snow showers and snow flurries?

These terms are sometimes used interchangeably when referring to light snowfall. However, they do have slightly different definitions.

A flurry is defined as a light snow shower, lasting for only a short period of time. The definition for a snow shower is a brief period of snowfall in which the intensity can be variable and may change rapidly. We try to use these words within their descriptions. If flurries are in the forecast you can expect a quick, light snowfall, with usually little or no accumulation.

When snow showers are in the forecast we are looking for off and on snow, which could accumulate up to a few inches over a given period of time. If heavier or steadier snow is expected, well try to be more descriptive in the wording of coverage and intensity.

What determines a blizzard?

According to definitions provided by the American Meteorological Society and the National Weather Service (NWS), a blizzard is a severe weather event that lasts at least three hours. It is characterized by low temperatures, high wind, and reduced visibility due to falling or blowing snow. Specifically the NWS says that wind speeds must be 35mph (or greater) and visibility less then one quarter mile. No official temperature for a blizzard is given, but the definition states that the combination of wind, snow, and poor visibility increases life-threatening conditions when the temperature falls below 20 degrees Fahrenheit.

You often refer to the Tug Hill Plateau while forecasting snowfall. What notable towns are included in this region?

Here's a few of the most notable towns in terms of snow records. The small town of Hooker on the tug recorded 466.9 of snow in the winter of 1976-77. The monthly record for snow accumulation belongs to Bennet Bridges and is 192 in January 1978. The official record for a one day snowfall in NY State belongs to Montague NY. The town had 77 of snow in 24 hours on the 11th/12th of January 1997. Montague also holds the single storm record for snowfall in NY with 95 from January 10th-14th in 1997.

The Tug is nearly 2,100 feet in elevation and is considered the snowiest place in the U.S. east of the Rockies.

Top ten list of the greatest seasonal snow totals in Rochester, since 1884

1. 1959-60 : 161.7"
2. 1977-78 : 160.9"
3. 1970-71 : 142.7"
4. 1900-01 : 141.5"
5. 1958-59 : 140.6"
6. 1978-79 : 138.5"
7. 2000-01 : 132.5"
8. 1992-93 : 131.5"
9. 1899-00 : 131.3"
10. 1957-58 : 130.8"

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