Closing out the Year: December 2016

Posted: January 3, 2017, 7:15 pm by spatrick

Hoar frost that developed on Meteorologist Matt Potter's car in northeast Philadelphia on Christmas morning.

December of 2016 was certainly different from recent ones. Unlike the past two winter seasons that featured above average temperatures and well below average snowfall for the entirety of the Northeast, this December actually featured some cold shots and decent snowstorms. While the pattern was variable with available but not long-lasting cold shots and interjecting warm surges, many were excited to see their first flakes/accumulating snow or contend with ice storms to get the winter going. The most notable storms across the Northeast this past month occurred on December 17th and December 29th. While colder systems were relatively lacking in the mid-Atlantic, there were a couple of low-end events to start the winter off right. Although it was a seemingly active December, much of the Northeast and parts of the mid-Atlantic are still suffering from abnormally dry to extreme drought conditions.

Monthly summarized snowfall totals, as reported by airports across the mid-Atlantic and Northeast, for December 2016. Image courtesy of SC-ASIS.

While there were numerous snow and ice events mainly across the Northeast, with just a few minor events in the mid-Atlantic (see the graph above for an overall monthly summary), two storms we will highlight for the month of December include the 17th and 29th systems. On December 17th, even the mid-Atlantic got into some wintry mix as well as significant icing as the storm moved in during the early morning hours in Maryland, and stretched northward into Massachusetts and southern New Hampshire. The "highest" totals (2-4") of snow and sleet were in Pennsylvania and New Jersey thanks to the storm coming in at the right place and at the right time. Maryland and Virginia were too warm to receive more than an inch of snow and sleet accumulation, but received 0.10-0.30" of ice since the storm arrived during the early morning hours, giving them sufficient time to ice before the midday sun helped to thwart additional ice accretion. Meanwhile, New England received just some glazes of ice as the storm came in during the daytime.

The next potent low-pressure system swung into the Northeast and mid-Atlantic on December 29th. While much of Maryland struggled to see accumulations except near the PA border, the heaviest snowfall within Pennsylvania, New Jersey, and New York were confined to the inland/elevated areas as primarily rain fell towards the coasts. The highest accumulations fell within New England in a strip from central Massachusetts up into southern New Hampshire, with widespread 5 - 10" totals, with much of it falling on the back-end of the system. This was due to the low pressure system "maturing", resulting in heavier snow wrapping back in before the storm exited overnight.

While temperatures swung throughout the month between warm surges (notice the highest high temperatures in the table below were 15-25 degrees above the normal high temperatures for the month of December) and cold surges (single digits and teens in mid-December), temperatures as a whole for December 2016 actually averaged out relatively near to only slightly above normal as a result. These temperature swings combined with frequent inland-tracking storms resulted in snowier conditions in the elevated inland spots, while coastal locations saw more rainmakers than wintry precipitation. For those in-between, December resulted in numerous wintry mix storms involving slushy snow, sleet, and freezing rain, thereby hampering overall snowfall totals.

Inland areas of New England saw slightly above average snowfall, while most other areas across the Northeast and mid-Atlantic came out below average. As noted in the table below, Manchester, New Hampshire and Windsor Locks, Connecticut received 23.0" and 10.2" inches, respectively, for the month, well above their 13.0" and 7.4" monthly averages. Meanwhile, Philly south into Maryland have only witnessed tenths and traces of snow as many systems were inland and therefore warmer, preventing cold air from taking hold to allow for measurable accumulations. Due to the southern warmth, Richmond, Virginia ended up with a whopping 0.0" for December snowfall.

December 2016 monthly liquid precipitation and snowfall compared to the normal December liquid precipitation and snowfall.

Regardless of actual snowfall, all locations are below-average in terms of liquid precipitation, which is not helping the ongoing drought conditions. There is still a large swath of extreme drought (D3) within Massachusetts and Connecticut, as well as moderate to severe drought conditions in New Jersey and Pennsylvania.

Drought conditions across the Northeast as of December 27, 2016. Image courtesy of the USDA.

Director of Forensic and Data Services / Lead Meteorologist
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