**A cold pattern in January with some staying power...becoming stormy as well**
Paul Dorian
Road conditions can quickly deteriorate on Tuesday morning as a band of snow and ice moves into the DC-to-Philly-to-NYC corridor likely between the hours of 6 and 10am. In all of these areas, ground temperatures should be quite low and susceptible to slippery conditions given the recent cold snap. Map courtesy NOAA, tropicaltidbits.com
Overview
The lowest temperatures so far this season greeted the new week in the Mid-Atlantic region with single digits in many suburban areas along I-95 and as low as ten below in the Poconos of northeastern PA. In fact, this morning’s temperature readings were the lowest in many spots of the Mid-Atlantic since about Christmas time two years ago when a brief, but severe cold snap hit the area. An Arctic high will weaken and shift offshore tonight and then low pressure to our north will bring a period of snow and ice on Tuesday morning. While this won’t be a heavy precipitation event on Tuesday morning, a burst of snow and ice can certainly cause problems on roadways which are quite cold given the recent chill.
Looking ahead, there are plenty of signs for a cold pattern to emerge in January with a deepening trough of low pressure likely to form over the eastern states. This upcoming cold pattern is likely to have some staying power as well given the development of strong high-latitude blocking across Canada. Numerous teleconnection indices support the notion of a cold pattern in January for much of the central and eastern US. In addition, given the potential positioning of the trough in the central and eastern US, the southern branch of the jet stream may very well become quite active which enhances the chance for snowstorms in an overall cold pattern.
Snow is more likely than ice early Tuesday in the Philly-to-NYC corridor; however, sleet and/or freezing rain is more likely than snow in the DC-to-Baltimore corridor…any one of these precipitation types can cause slippery road conditions. Map courtesy Canadian Met Centre, Pivotal Weather
Tuesday AM threat of snow and ice
It won’t be a heavy precipitation event; however, a band of snow and ice can wreak havoc on roadways during the morning hours on Tuesday all along the DC-to-Philly-to-NYC corridor. As low pressure pushes to the north, it’ll drag a front through the Mid-Atlantic region and a band of snow, sleet and/or freezing rain is likely to pass through the I-95 corridor in the hours between 6 and 10 am.
Single digits were commonplace early Monday in many of the north and west suburbs of the big cities along the I-95 corridor. In fact, temperatures were at their lowest levels in about two years in many of these spots since a severe cold snap that took place around Christmas time of 2022. Furthermore, with an official low temperature of -1°F this morning in the Wilkes-Barre/Scranton area, it’s the coldest December morning since 2005 (credit Mark Margavage (X)). Map courtesy NOAA, Dr. Ryan Maue (X)
Given the recent cold, roadways are likely to be quite conducive to slippery conditions with any snow and/or ice that falls on Tuesday morning. There can be a coating to an inch of snow in many spots early tomorrow and a glaze of ice is also possible; especially, in the DC-to-Baltimore portion of the I-95 corridor (snow more likely from Philly-to-NYC). The precipitation winds down by mid-day and partial sunshine should be the rule on Tuesday afternoon as well as on Wednesday, Christmas Day.
An Atlantic Ocean trough of low pressure (shown in blue) will tend to “retrograde” to the west and into the eastern US as we begin January and at the same time, higher pressures than normal will form over much of Canada (shown in orange). This kind of combination in the upper atmosphere is typically colder and potentially stormier for the central and eastern states. Cold air masses can be transported (indicated by arrows) all the way from northern Canada into the continental US. Map courtesy ECMWF, tropicaltidbits.com
January cold pattern likely with some staying power
Looking ahead, numerous signs point to a cold pattern to develop in early January across the central and eastern states and one that is likely to have some staying power. A deep low pressure trough over the Atlantic Ocean will tend to retrograde back to the eastern states early next month and at the same time, high-latitude blocking will setup across Canada. Teleconnection indices such as the AO, NAO and EPO all support the idea of a cold pattern in January across the central and eastern states.
Teleconnection indices known as the Arctic Oscillation or AO (left) and its closely related cousin known as the North Atlantic Oscillation or NAO (right) will slide into “negative” territory as we end December and begin January and this is usually correlated with “high-latitude blocking” that forms over Canada with higher pressure than normal. This kind of an upper-level pattern typically is more favorable for the transport of cold air masses from northern Canada into the central and eastern US during a winter season. Plot courtesy ECMWF, Weather Bell Analytics
All three of these teleconnection indices slide into “negative” territory by early January and this is usually correlated with an overall upper-air pattern that favors the transport of cold air masses from northern Canada into the central and eastern US. The combination of strong high pressure over Canada and a deepening trough over the central and eastern US should inhibit mild Pacific Ocean air from impacting the US and allow for air masses from way up in Canada to drop south and east and into the Lower 48.
A teleconnection index known as the Eastern Pacific Oscillation or EPO will slide into “negative” territory as we end December and begin January and this is usually a deterrent for mild Pacific Ocean air to cross the continental US as can happen during a winter season. Plot courtesy ECMWF, Weather Bell Analytics
In addition to the teleconnection indices, the Madden -Julian Oscillation or MJO will be rotating into phases 7 and 8 during the next ten days or so and these locations are typically correlated with colder-than-normal pattern across much of the central and eastern US. The MJO tracks a tropical disturbance as it moves around the globe on a regular basis and its location or phase can help determine temperature and precipitation patterns in other parts of the world.
The Madden-Julian Oscillation or MJO is likely to move into “phases” 7 and 8 as we end December and begin January and these particular locations of a tropical disturbance generally are correlated with colder-than-normal temperatures across the central and eastern US. Plot courtesy ECMWF, NOAA
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com