Almanack Weather Prognosticator Chad Merrill
December: Crank up The Heat Even More!
We look to the warning signs in the weather pattern to see what December has in store. These warning signs are teleconnection patterns that lead us to follow the jet stream across the Northern Hemisphere and see if it will bend north of western Maryland and the Potomac Highlands and bring warm weather or slip south and bring winter cold and precipitation.
Two of these patterns point to a full-throttle nose dive into winter. The North Atlantic and East Pacific Oscillation will trend in a negative phase starting a few days into December through the first day of winter (December 20). When working in conjunction with each other, these patterns in their negative phase unleash a cold pattern from Canada and lead to below-average temperatures. The West Pacific will likely transition out of a negative phase early in December, so this will likely cut-off potential for a cross-polar flow that would chill temperatures to record levels.
One interesting pattern that will also dominate is a negative phase of the Pacific North American (PNA) pattern. This will favor multiple storms crossing into the Northwest and northern California before pushing across the U.S. A conventional storm track with a negative PNA keeps systems west of the Appalachians and places the region on the warm, rainy side. However, given the upstream blocking over Greenland, the storm track will be forced south of western Maryland and the Potomac Highlands, leading to occasional rounds of snow.
Our forecast is for above-average snow, which means 5 to 7 inches in Cumberland, 11 to 16 inches in Frostburg and more than two feet in Garrett County. The earlier start to winter (compared to last year) will allow local ski resorts to thrive on the more sustainable cold pattern to build a stable base heading into January.
We also see a statistically more significant chance of a White Christmas this year compared to years passed despite a warming trend expected in the last week of the month. So, this means a better than 50-percent chance in Cumberland and higher than 75-percent chance on the Allegheny Plateau.
The early winter season cold shots will increase the lake-effect snow chances in the Great Lakes. A north to northwest wind is the most favorable wind direction for Garrett County to cash in on several inches of snow. Incidentally, the reason for the recent historical snow amounts in southwest New York was a favorable and sustainable southwest wind over Lake Erie. This wind direction allows air to flow over the longest stretch of Lake Erie (since it’s oriented southwest to northeast).
Drought covers 59-percent of the U.S. as of late-November, with the Plains and California suffering the brunt of the precipitation deficits. The West Coast relies on Pacific winter storms to replenish water loss during the summer and December will help deliver a small fraction of the moisture needed to keep drought from expanding. The Northwest and northern Rockies will see the greatest precipitation surplus in December with moderate drought easing from the coast to the Cascades. Little drought recovery will occur in the nation’s midsection to the Ohio and Tennessee valleys, with a storm track favorable for one or two episodes of snow, sleet and freezing rain.
The Southwest into the Southern Plains and Lower Mississippi Valley will be the warmest spots in December while the Pacific Northwest to northern Plains stay the coolest. The Rockies ski season will get a boost from Mother Nature in December.
The Hagerstown Town and Country Almanack wishes everyone a happy and healthy Thanksgiving weekend and Christmas! Feel free to reach out if you wish to purchase a 2023 Hagerstown Town and Country Almanack as they make great gifts and stocking stuffers for Christmas!
We’ll see you back here before we ring in the new year to discuss January weather trends across western Maryland and the Potomac Highlands.