A Wintry Start to December, Mild End

After a quiet November, we immediately fell into a long duration storm that took up the few days of December. While this was a significant storm for New England with at least some accumulations down into the northern tier of the Mid-Atlantic, much of the month was riddled with nickel-and-dime accumulation events. Most of these fell during the first half of month, but let’s take a look into what happened.

As alluded, the pattern swiftly changed to allow for a system to impact the Northeast over the span of three days between the 1^st and 3^rd. The first half of the system was generally a wintry mix across southern New England into northeastern PA. After a slight lull in accumulations, over a foot fell across many parts of northern Connecticut and interior Massachusetts, and even up to two feet across northern Worcester County! The heart of the storm featured snowfall rates up to 3” per hour, which packed quite a punch upstream along the Hudson River and east across the Connecticut River Valley.

The next two weeks would then be quite active. Following a few snow shower or light mix events, a system swiftly trekked across the area on 10^th and 11^th, resulting in several inches of snow up and down the I-95 corridor. Even much of the area south of the Mason-Dixon Line into northern Virginia saw a few tenths (up to 1” around Westminster, MD). Ironically enough, the initial warm push before this system resulted in temperatures over 10 degrees above normal in the 50s and even low 60s before the colder air pushed in.

After the ensuing cooldown, an ice storm impacted the area on the 16^th and 17^th, which initially came down as sleet before quickly turning to freezing rain. Several tenths of icy glaze accumulated with peaks up to 0.50” across parts of the Hudson Valley into central Connecticut! Thousands were left without power on top of treacherous road conditions. Right on the heels of that storm was a powerful cold front into the overnight on the 18th that pushed snow squalls across New England and the Mid-Atlantic, plunging areas across northern NJ and even New York City into brief, yet heavy snow and low visibilities. Despite warnings, a massive pile-up unfortunately resulted from these squalls on Interstate 80 in Union County out in central Pennsylvania.

After all that, we entered an almost eerily quiet period of weather that persisted until just after Christmas. High pressure prevented any precipitation from developing, providing sunny days and clear nights. Temperatures regularly jumped form the 40s and 50s to back below freezing. While there was no precipitation, there were mornings when pavements became wet because of the combination of cold surfaces, residual salt, and just enough moisture hanging in the air. Some this actually resulted in frost on the pavements where it was cold enough.

Pavement frost in eastern PA, December 24, 2019

The holiday stretch was then warm as temperatures were up to 10 to 15 degrees above normal, which gave a warm, yet “brown” Christmas. Highs regularly hit the 50s and even 60s though this was not quite record-breaking. The 29^th and 31^st marked the last system of the year and was mostly a rain storm, though it did have a few quirks. While it rained for the vast majority of the region, it snowed and sleeted across the interior Hudson Valley into Massachusetts. Interestingly enough, if one happened to be across the highest elevations of the region, such as High Point, NJ or parts of Litchfield County in Connecticut, it was just cold enough to cause significant icing across areas that were around 1300’ and up. Most of this was out before the ball dropped on New Year’s Eve, which felt more “seasonable” than previous years, with temperatures in the 30s.

As far as snowfall totals, most of the month was below average unless you were caught under the foot plus event in New England at the start of December (some areas are over 12” above normal at this point). Others did not fare as well from Philadelphia on south, where only a few tenths of an inch fell, with many spots 3 to 5 inches below normal so far. While not a record breaking month, there were some precipitation records to note. Hartford, CT (and really thanks to the first storm) saw its third wettest December on record at 7.93”. New York City also witnessed its 5^th wettest month on record at 7.09”. Hartford in particular saw its 4^th snowiest December on record at 22.0”!