Greetings, Western Maryland and the Potomac Highlands! December treated winter weather enthusiasts well. I hope today’s article finds everybody healthy and having a great holiday thus far.
Now, the big question on everyone’s mind is the prospect for more cold weather and snow in January. Let me tackle that question and outline the Hagerstown Town and Country Almanack predictions for the start of 2021.
First of all, references to specific geographical features as they relate to Western Maryland can be found here: https://en.wikipedia.org/wiki/Ridge-and-Valley_Appalachians#/media/File:Appalachian_map.svg. For those without access to internet, the map found via this link shows Garrett County located on the Allegheny Plateau while state Route 36 parallels the eastern Allegheny Front. The remainder of the Potomac Highlands east of this boundary is considered in the ridge and valley Appalachians.
Now, let’s focus on the weather forecast going through January. I look to the teleconnection patterns, a large-scale pattern of atmospheric pressure and circulation anomalies, that dictate day-to-day weather, to see trends for January. The North Atlantic Oscillation (NAO, for short), a pattern of atmospheric pressure between low pressure near Iceland and high pressure near the Azores, trended mostly negative in December, leading to more snow and cold blasts than I expected.
Moving forward through January, I see the NAO trending even more negative as the month goes on. This means near-to-below average temperatures will greet the Potomac Highlands, with the coldest weather occurring in the final two weeks of January.
Not to be outdone, the stratospheric polar vortex is showing signs of weakening and experiencing a significant warming by late January. In short, a strong polar vortex, such as what the Northern Hemisphere experienced last winter, keeps the cold air bottled up at the Arctic Circle. A weaker polar vortex allows short episodes of cold air to move about the Northern Hemisphere such as the rounds of cold weather we had in December.
A significant warming event would completely throw the vortex off its rocker and bring extended cold weather to parts of the Northern Hemisphere. The long-term cold outbreak (likely three to four weeks in duration) would likely make its way around the Northern Hemisphere and eventually into Western Maryland. I expect Western Maryland will see sustainable long-term cold from a stratospheric warming event after Jan. 5.
I see chilly conditions in the first week of January with two cold fronts that will bring light snow, perhaps mixed with sleet. In wake of each front, a few snow showers will bring additional accumulation in the Alleghenies. Another storm system between the 12th and 15th will bring more snow to the Potomac Highlands.
In January’s second half, the time frame from the 21st through the 25th and 29th to 30th offer the best opportunity for widespread winter precipitation.
In the last 20 years, Cumberland has averaged four days in January with more than a dusting of snow while Garrett County averages 10 January days with measurable snow of more than a dusting. Garrett County sees on average 21 inches of snow in January while Cumberland typically accumulates half that amount in the first month of the year. As for overall precipitation (rain, plus melted ice, sleet and snow), Allegany County averages 2.76 inches while Garrett County averages 3.77 inches.
I expect these climate averages for January will hold true. So, the Allegheny Plateau will likely see at least two feet of snow and a total of 3.5 to 4 inches of precipitation while the ridge and valley part of the region will likely see about 15 inches of snow and a little more than 2.75 inches of total precipitation. I don’t see upside potential to a colossal Western Maryland snowstorm in January but rather several small to moderate events that will add up to more than average snowfall.
Feel free to continue providing feedback to these monthly outlooks and if you wish to purchase the 2021 Hagerstown Town and Country Almanack, don’t hesitate to contact me. Have a great holiday season and stay safe and warm!
Chad Merrill is a Cumberland native and meteorologist who serves as the Hagerstown Town and Country Almanack weather prognosticator and senior meteorologist at Earth Networks in Germantown. Merrill previously was a meteorologist with WDVM (formerly known as NBC25) in Hagerstown and WJAC-TV in Johnstown, Pennsylvania. Merrill can be reached at 240-285-8476 or by email at email@example.com.