Computer forecast models are becoming better aligned on the idea that a significant winter storm will come together and impact portions of the Mid Atlantic and Northeast later this week. With the threat of a winter storm growing, the National Weather Service is carefully reviewing computer model forecast data, ground, air, and satellite based observations, and climatological trends to understand the threat. Winter Storm Watches or Warnings may be required in the coming days.

Some computer forecast guidance suggests that a cut-off upper low tracking tracking across the Mid-Atlantic on Thursday will join forces with a secondary surface low cyclogenesis right along the Mid-Atlantic coast. This scenario would likely bring widespread impacts along the I-95 corridor from Washington, DC all the way to Boston, MA.  But the computer forecast guidance isn’t entirely aligned. Some other forecast models are less amplified and aggressive with the trough, simply swinging the base of the trough off the coast with any secondary low development shunted well out into the western Atlantic. If that were to happen, there would be much less, if any, impacts to the Northeast.

The National Weather Service office in Philadelphia wrote in today’s Forecast Discussion, “Ensemble guidance though, does support secondary coastal low development, so this system will need to be closely watched over the coming days to see how close this system may be to our coast.”

Currently, forecast models are suggesting this system could develop next Thursday and/or Friday.