January Thaw Ongoing For Now, Winter Making A Return Towards Next Week

With days as of this past week constantly being int he 50’s and even 60’s, many wonder where did winter go? Normally in the winter months across the lower 48 go through a longer duration warming trend as a recharge of the overall pattern and sign are pointing at a return to more winter weather […]

With days as of this past week constantly being int he 50’s and even 60’s, many wonder where did winter go? Normally in the winter months across the lower 48 go through a longer duration warming trend as a recharge of the overall pattern and sign are pointing at a return to more winter weather moving back across the eastern half of the US.

Weather models are all onboard for a bigger shift in the overall weather pattern across the Northern Hemisphere Mainly what’s going on across the Pacific Ocean which is the biggest driver to the Lower 48 weather pattern for supplying the cold air and the active storm track. One thing that is peaking my interests is a significant drop in the Eastern Pacific Oscillation during the time period of the 14th-20th.

A very large negative Eastern Pacific Oscillation, or EPO, is a significant large scale weather pattern that can strongly influence temperature and storm tracks across the United States, especially during the fall and winter months.

When the EPO is strongly negative, a powerful ridge of high pressure builds over the eastern Pacific, often near Alaska and the Gulf of Alaska. This ridge acts as a blocking feature, forcing the jet stream to buckle sharply northward into Alaska and then dive southward downstream into western and central North America. As a result, Arctic air is displaced south out of Canada and into the United States.

For the western United States, a negative EPO often brings colder than normal temperatures, particularly to the Pacific Northwest and northern Rockies. The ridge offshore can suppress precipitation along parts of the West Coast, leading to drier conditions in California, while the colder air aloft supports snow in the higher elevations of the Northwest and Intermountain West when storms are able to undercut the ridge.

Across the central and eastern United States, the downstream response to a negative EPO is often a broad trough, which allows cold air to spill southward. This can lead to below normal temperatures across the Plains, Midwest, and East Coast. When moisture is available, this pattern can be favorable for winter storms, as cold air at the surface can interact with southern stream systems or coastal lows.

The strength of the negative EPO matters. A weak negative phase may only produce brief or modest cold shots, while a strongly negative EPO can support prolonged cold outbreaks, sometimes reaching deep into the southern United States. This setup can also increase the likelihood of sharp temperature swings if the blocking ridge eventually breaks down.

Weather across the Eastern US might get very interesting going forward into the mid-month.