Garrett County’s unique location and elevation situates the county in somewhat of a “sweet spot” for snow. Since 1970, Garrett County has averaged 138 inches of snow annually. This is due to several factors that allow Garrett to participate in a variety of snowfall events. The county sits atop the Appalachian Plateau, and as such elevations are generally over 2000 feet above sea level. Deep Creek Lake is roughly 2400 feet, Wisp Mountain is roughly 3100 feet, and Backbone Mountain, the highest point in Maryland, reaches 3360 feet. Thus, because of the elevation, temperatures in the county are usually 7-10 degrees colder than the nearby valley areas of western PA, WV, and 10-15 degrees colder than eastern MD DC and VA.
Types of Snowstorms that affect Garrett County
- Upslope snow
Upslope or upsloping refers not so much to a type of snow event, but a characteristic of Garrett County and the surrounding mountains that permits more snowfall than otherwise might occur. Upslope snow or upslope enhanced snow occurs when wind blowing across the relatively flat elevations of the Ohio Valley runs up into the Appalachian mountain range. As the air hits the mountains, it is forced upward. Any moisture at the surface lifts upward, condenses, and forms low clouds above the ridges. Eventually those clouds will precipitate. In a sense, the mountains are “wringing out” the moisture in air like squeezing a wet towel. See the graphic below from UCAR. The more perpendicular the winds are to the mountains, the greater the upslope forcing will be. The upslope phenomena produces mesoscale (small) weather events where while there may be only flurries in the lowlands of SE OH, Western PA, and WV, but yet very heavy snows across the Appalachians. While the upslope phenomena can lead to its own snow events, it also can enhance lake effect snows, frontal passages, as well as macroscale or large scale systems described below.
- Lake Effect Snow
Lake Effect snow occurs when winds out of the northwest blow across Lake Erie. The winds act to pick up the moisture laden air that sits over the Lake (like steam over a pot) and push it over the land masses to the southeast. As the moisture laden air hits the higher elevations it produces snowfall. See graphic below from UCAR. Both lake effect and the upsloping phenomenon will often work hand in hand to provide Garrett County with the consistent day to day snowfall that Garrett County is renown for.
- “Nor Easters”
Generally, Nor Easters are Macroscale (large) storm systems that occur over the northeastern United States. They get their name from the associated wind direction which comes from the northeast.
A Meteorologist, Dr. Miller, classified Nor Easters into two Categories, now named “Miller A” and “Miller B.” Miller A storms originate near the Gulf of Mexico and propagate up the Atlantic Coastline. Miller B storms usually cross the country at higher latitudes, similar to Manitoba Maulers (below), but then redevelop a coastal low over the Atlantic Coast. Generally speaking, Miller A storms are bigger snow producers for Garrett County given that the consolidated low pressure system is organized as it climbs the Atlantic Coast, whereas Miller B storms tend not to produce as much snow, given that often redevelopment of a coastal low will rob energy from the primary low crossing the country, and the redevelopment occurs too late to provide the area with the heaviest snows; Miller B’s often bring heaviest snows to the New England region.
Nor Easters predominantly track from the SE U.S. and either on or up the Atlantic Coast. Also unlike clippers, these systems do often tap into Gulf moisture as well as moisture from the Atlantic Ocean. Garrett County will occasionally miss out on a Nor-Eastern given its western location, but generally speaking, most Nor-Easter’s will at least clip Garrett County with some snow, and very many that “hug” the coast, provide Garrett with its most substantial snow storms. Examples: March 13th 1993, Jan 4, 1994.
- “Manitoba Maulers”
Meteorologists often nickname certain types of low pressure systems from the area in which they originate. Manitoba Maulers originate in the Provence of Manitoba Canada and move SE. Generally these systems will dig a little deeper than an Alberta clipper, and therefore, tap into more moisture from the Gulf of Mexico. The result is that generally these systems can produce more snow for Garrett County along with upslope enhancement, and often can bring 4 to 12 inches.
- “Alberta Clippers” (upslope enhancement)
Alberta Clippers, nicknamed Alberta because of the Provence in which they originate, and clipper, because of their fast movement, generally do not tap into much moisture from the Gulf of Mexico and as such, generally only provide lighter snows, often in the 4 to 8 inch range. Some intense clippers however have given Garrett County 10 to 12 inches of snow.
To summarize, while some areas in the east are known for their lake effect snows like Erie or Buffalo, and others for their propensity for coastal storms such as Boston or Albany, Garrett County is perfectly situated to benefit from several types of weather systems and thus explains why the County typically averages over 100 inches annually.
- Ice Storms (Cold Air Damming)
Again, due to Garrett County’s peculiar geographic placement and elevation, the area also very often experiences ice storms fueled by a phenomena called Cold Air Damming (CAD). This occurs when low pressure centers associated with large weather system track to the west of the Appalachians. Generally, the northwest side of a low pressure system is the cold sector and the SE side is the warm sector. As described above with Nor Easters, when they track to Garrett County’s east, Garrett is in the cold sector and experiences snows. However, when a low pressure tracks to the County’s west, it pulls warm air from the Gulf of Mexico Northward. As this warm air hits the mountains it is forced up and over the existing air mass. The existing air masses cold temperatures are trapped at the surface, and, when high pressure is located to the County’s North, the high pressure’s clockwise flow will dam the cold air up against the mountains from the east. The resulting dichotomy of the air mass is often cold, subfreezing air at the surface, and warmer air in the top layers of the atmosphere. See the graphical depiction below from MIT. As precipitation falls through the atmosphere it melts, but then refreezes again as it falls into the subfreezing surface boundary. Garrett County has experienced many memorable ice storms as a result of cold air damming.