Just wait an hour and the weather will change, that is a popular and over used statement that people use when describing the weather in Northeast Ohio and Western Pennsylvania. However, nothing could be truer when you have to forecast for this region of the country, especially during the winter. The reason it’s so difficult to forecast, is simple, all you have to do is blame Lake Erie. The lake and the different elevations in this region can be a nightmare for a forecaster. However if you look at the averages and trends over the years you can make your job of lake-effect snow forecasting easier. Of course it’s all about your location near the lake and several other factors such as water temperature, air temperature, wind speed, and direction. If you get this down then you have a better chance of getting in the ballpark, but it’s still a tricky forecast to nail down. Seasonal snow amounts in Ohio vary at the end of each season. In the figure below you will notice the heaviest snowfall in Ohio occurs in the northeast section of the state. This would also extend over the boarder into Pennsylvania.  The reason for higher averages in this region is because of lake-effect snow. This area is called the snow-belt due to its higher elevation and proximity downwind of Lake Erie. Portions of southern Lake, Geauga, Ashtabula, and northern Trumbull counties can see anywhere from 85 to 100 inches on average each season. While the secondary snow-belt, of southern Trumbull and Mahoning counties in Ohio can see anywhere from 55 to 75 inches of snowfall on average. This can also extend into Mercer and Lawrence counties in Pennsylvania. These areas have the highest risk of heavy snowfall, but if conditions are right snow off the lake can extend even farther south. You can see snowfall totals even farther south into Columbiana and Stark counties can reach anywhere from 40 to 55 inches annually during one season. To fully understand the effect the lake as on snow forecasting we must define lake-effect snow. According to the National Weather Service, lake-effect snow is generated from the temperature contrast between cold artic air moving over the relatively warm waters of the Great Lakes. The cold air picks up moisture over the open waters and the deposits it in higher elevations downwind from the lake. This primarily occurs between the months of November and February. Some of the heaviest lake snow events occur in the fall and early winter and then again even in early spring. This happens because as the lake temperatures cool in the dead of winter the lakes begin to freeze and that reduces the threat of lake-effect snow. However each lake is different, Lake Erie is the shallowest of all the great lakes so while it may freeze sooner, it also will melt sooner, allowing Northeast Ohio to see heavy snow amounts in late winter and early spring. Lake effect snow can be compared to real estate; it is all about location, location, and location. I am a forecaster in Youngstown, Ohio which is on the Ohio and Pennsylvania border. My forecast region extends north into the high ground of Trumbull and Ashtabula counties in Ohio, and the high ground of Mercer and Northern Lawrence counties in Pennsylvania. However, I also forecast south of the city into Mahoning, Columbiana, and Stark counties in Ohio and southern Lawrence and northern Beaver counties in Pennsylvania. The northern viewing area is higher in elevation then the southern sections of the viewing area, plus it is closer to Lake Erie. One may think it would be easy to forecast snow amounts, with larger amounts North near the lake and little if any south, but that’s not always the case. The speed and direction of the wind carrying the lake-effect snow can make all of the difference. This is called the fetch which according to the National Weather Service, means the wind must pass across at least 80km of lake surface before the lake-effect snow will form. The larger the fetch increase the chances for a greater lake-effect snow event. The challenge we have here in the region is that if the direction of the fetch changes then our snow forecasts are thrown out because heavier snowfall will fall in a different location. A fetch directly out of the west will allow the snow to hug areas closer to the shore of Lake Erie. Regionally this brings the snow into far Northeast Ohio, Erie Pennsylvania, and Buffalo, New York. While locally, snow squalls could form and heavier snow will fall in Ashtabula, northern Trumbull and northern Mercer counties. Anywhere from 6 to 12 additional inches could fall in these areas, while just 25 to 50 miles south into Youngstown, an accumulation of less then 4 inches could fall. However if the fetch is more out of the Northwest then that brings the snowfall into the secondary snow belt including Mahoning, Columbiana, and Stark counties in Ohio. Heavier snow totals can also form in Southern Mercer and Northern Lawrence counties in Pennsylvania. A forecaster must check wind direction constantly to stay on top of lake-effect snow, especially when the fetch carries the snow upslope into higher elevations, where accumulations can significantly increase. It is not uncommon for one lake-effect snow event to produce 2 or more feet of snow in a 24 hour period, leaving much room for error. I remember hearing a meteorologist once say, Lake-effect snow is much like throwing a dart at a dart board, you never know where it will end up. This is so true, by just looking at the averages of snow amounts in Ohio; you know the northern sections will obviously see more snow each and every year. However, that to can vary if the fetch one season is more out of the northwest, rather then the west. In fact the 2006 and 2007 season has shown to prove that theory correct. In Youngstown we usually average 56 inches of snowfall on a season, this year however we have seen 89.2 inches of snowfall. This breaks the previous record of 86 inches of snow making it the snowiest season in history for Youngstown, Ohio. This can only be blamed on one thing, Lake Erie. Most of our lake snow events featured a fetch out of the northwest bringing the snowfall directly into the region. Then a late winter thaw helped to open the waters of Lake Erie, leaving them prone to produce more lake-effect snow in the event of another cold snap. As of the writing of this paper, this has happened as we are experiencing the second snowiest April on record. A cold snap of air over the open waters of Lake Erie has created a spring that many in this region will never forget. Proving averages and trends can most certainly be broken. In conclusion I go back to an earlier statement I made comparing lake-effect snow to real estate, it’s all about location, location, and location. We have proven that each county in this region of the country can different snow totals, just depending on which way mother nature chooses to blow her blustery arctic air across our Great Lakes. Works Cited Page National Weather Service. “Glossary”. 10 April 2006 http://www.erh.noaa.gov The Weather Doctor. “Lake Effect Snow”. 11 April 2006 http://www.islandnet.com/~see/weather/elements/lkefsnw1.htm Ohio Department of Transporation. “Snow Map”. 10 April 2006 http://www.dot.state.oh.us/snopmap.htm |