9:45 AM (Monday) | ****Very cold and active pattern to set up in early January with some staying power…may feature extreme cold and multiple snow threats…next week looks particularly interesting****

December 30, 2024Paul Dorian

A much colder-than-normal weather pattern will set up for the central and eastern US during early January and it looks like it’ll be one with some staying power. In fact, this upcoming cold stretch for much of the nation may feature some extreme cold and very cold conditions may penetrate all the way into the Deep South from Texas-to-Florida. In addition, there are likely to be multiple snow threats in this developing weather pattern that can impact much of the central and eastern US to go along with the expected much colder-than-normal temperatures. Next week looks particularly interesting in a period that may feature multiple snow and ice threats and potentially some extremely cold air. Numerous teleconnection indices support the notion of a much colder-than-normal weather pattern, and an unfolding stratospheric warming event enhances the idea that the much colder-than-normal temperature pattern can be sustained well into the month of January.

**A cold pattern in January with some staying power...becoming stormy as well**

December 23, 2024Paul Dorian

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.

***An upcoming active pattern with several signals (MJO, SSW, PNA) pointing to additional Arctic air outbreaks for the central and eastern US***

December 12, 2024Paul Dorian

The month of December has started off with a few Arctic air outbreaks into the central and eastern US and while the overall pattern may turn somewhat milder for part of next week, there are multiple signals pointing to additional cold air outbreaks from later next week into the month of January. In addition, the unfolding weather pattern appears to be quite active with numerous storm systems to deal going through the second half of the month of December.

One of the signals for additional cold air outbreaks revolves around an oceanic-atmospheric phenomenon known as the Madden-Julian Oscillation or MJO. A second centers around a phenomenon that features warming over the polar region in the upper part of the atmosphere known as the stratosphere. Finally, a teleconnection index known as the Pacific-North American (PNA) is likely to feature a positive phase for much of the rest of the month and this generally favors high pressure ridging across the western US and Canada which, in turn, is usually favorable for cold air outbreaks to make their way from northern Canada into the central and eastern US.