Cold air returns ahead of potential storm

Behind a coastal system which brought widespread rainfall totals over 1″ on Sunday, colder air is filtering into the area and will settle in by the beginning of the new week. In fact, arctic air will pool to the north of our area over New England and much of Eastern Canada, as the Polar Vortex elongates and stretches from Central to Eastern Canada by mid week. The result, in our area, will be colder than normal temperatures with single digit and teen low temperatures possible over the interior.

The newer forecast models bring temperatures into the teens even in New York City and much of New Jersey by Tuesday morning. A few weak disturbances will pass by to the north of our area during the first half of the week, but aren’t expected to provide any significant precipitation. Other than a few snow showers, the first part of the week will simply be quiet and quite cold. But by weeks end, forecast models continue to signal a potential storm system which could provide the area with winter weather. The details, however, remain uncertain and likely won’t come into better focus for a few more days.

NAM model forecasting low temperatures in the single digits and teens throughout the area on Tuesday morning.

NAM model forecasting low temperatures in the single digits and teens throughout the area on Tuesday morning.

Late week snow potential remains, but situation is complicated: Yesterday we thoroughly discussed the potential for a winter storm in our area during the latter part of the upcoming week. Since then, not much has changed. Forecast models consistently have shown the potential for an event. However, the eventual breakdown of the more detailed pieces of the pattern remain highly uncertain — and likely won’t be fully understood until we draw a few days closer to the event itself.

The main culprit behind the storm system is the northern stream disturbance, which slides southeastward from the Pacific during the middle of the week. But the pattern evolving around that disturbance, which supports the potential for winter weather, is far more intricate. The beginnings of the change can be traced back to a high latitude blocking ridge which forms over Greenland during midweek. As transient and temporary as this block may be, it acts to slow down the pattern ever-so-slightly. To the south of this ridge, the Polar Vortex elongates over Eastern Canada to support an ample supply of cold air to the north.

GFS model showing the potential winter weather event shifting offshore with minimal impacts.

GFS model showing the potential winter weather event shifting offshore with minimal impacts.

So while the aforementioned northern stream disturbance swings into the Tennessee Valley, it will be entering an environment which could potentially favor a winter storm in the Northeast US. The issue, at this point, is attempting to understand just how the pattern will shake down. The variables mentioned above will have a tremendous impact on the sensible weather outcome. A weaker block, and the Polar Vortex shifts northward allowing the initial surface low to move northward as well. This would be a significantly less wintry outcome for our area. A stronger block, or better positioned Polar Vortex, and the pattern can slow down slightly more — allowing for further amplification.

Forecast guidance at this range should be used, as titled, for guidance only. After breaking down the pattern it becomes clear that slight changes in the forecast will create tremendous variance. So while confidence is increasing in a winter weather event somewhere in the Northeast, the details are likely not going to be understood with confidence until a few days from now.

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