Almanack Weather Prognosticator Chad Merrill





  December: The Door To Winter Opens!

Tuesday, November 23, 2021

Greetings and Happy Thanksgiving, western Maryland and the Potomac Highlands! Mother Nature has opened the Canadian gate this holiday weekend with a blast of seasonably chilly temperatures. November will close with very light to light snow and the first measurable accumulation east of the Alleghenies as a pattern transition occurs. Now the million-dollar question is, “Will Mother Nature keep flirting with winter or will we dive deep into the season with the flip of the calendar to December?”

The U.S. is well-established in a La Nina pattern with a barrage of Pacific storms pushing moisture into the Northwest with transient cold blasts making their way across the northern tier, including western Maryland and the Potomac Highlands. We have to look beyond the El Nino Southern Oscillation to see if there are any signs of a pattern change.

A couple of signals stand out; the first being the Madden-Julian Oscillation, or MJO. No, this signal was not named after the former coach of the Oakland Raiders and sportscaster John Madden (haha). This pattern describes the favorable ocean basin or continent where stormy weather is likely to occur and it has a direct link to altering the jet stream. The pattern is currently circulating through the West Pacific, which is only favorable for transient cold blasts in western Maryland and the Potomac Highlands. The MJO will likely head into Phase 8 about a week or so into December, which is more favorable for cold and wintry weather in western Maryland and the Potomac Highlands.

There are signs that winds around the Stratospheric Polar Vortex will weaken in mid-December, which will help dislodge cold blasts into the mid-latitudes. Additionally, the East Pacific Oscillation, or EPO for short, was in record positive territory this fall season. It is likely to transition back to a negative phase in mid-December. When this occurs, the cross-polar flow from northern Asia into Alaska sweeps into the U.S. with a series of winter storms that push from the central and southern Rockies to the Eastern U.S.

This autumn, the strong positive Eastern Pacific Oscillation was the reason why Denver (as of November 27) has yet to accumulate its first measurable snow of the season, demolishing the previous record of November 21, 1934. The positive EPO has been deflecting the storm track well north of the central Rockies.

December will begin warm and dry for western Maryland and the Potomac Highlands. By the end of the month’s first week, a storm system will bring a rain/snow mix. Gusty winds will occur in its wake with a trend towards colder temperatures. The crux of snow accumulation for December will occur right during the middle of the month. This will be followed by a gradual warming trend through the final week of the year, but just enough snow will still linger early on the 25th for many spots to see a White Christmas! The month will end with a low pressure that will push west of the Appalachians and bring rain, with potential for fog in the higher elevations surrounding Cumberland.

As for December snowfall, Cumberland averages 5.4 inches, Frostburg averages 11.8 inches and Garrett County traditionally accumulates 28 inches during the month. We are forecasting slightly more snow than average for December, but will caution folks that forecast model guidance, which is relied upon for snowfall forecasting, will be too bullish with amounts.

A sneak peak for the remainder of winter shows an average January for snowfall, with most of the snow accumulating at the end of the month. We expect February 2022 to be a flip-flop of last year when occasional snow and wintry mix occurred, but don’t go planting flowers on a mild, sunny February afternoon. We won’t be finished with winter quite yet.

All of us at the Hagerstown Town and Country Almanack wish our readers a very Merry Christmas and Happy Holiday! Thanks for your continued support of our publication. If you are looking for that last-minute gift idea, reach out to me at cmweather24@gmail.com and I will point you in the right direction to purchase a 2022 Hagerstown Town and Country Almanack! 


Chad Merrill
Almanack Weather Prognosticator

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. Feel free to contact him at cmweather24@gmail.com or 240-285-8476.