Jan 1: Thursday Winter Storm Signal Increasing

Jonathan Carr
By Jonathan Carr January 1, 2018 14:37

Jan 1: Thursday Winter Storm Signal Increasing

Discussion: After reviewing the latest data and live observations, I’ve noticed a few things. For one the low pressure system’s expected track in the Atlantic Ocean has trended not so much west, but has consolidated on the western side of the multi-low scenario that’s been on recent mid-range guidance. This would naturally bring all low-surrounding impacts (as a singular low) to the W as well. This would also allow a period of rapid intensification over warmer W Atlantic waters as the low tracks from the Bahamas to the N/NE.

I’m seeing modeled surface low pressure levels in the 965-970mb range when passing through our latitude well to our E. The system then goes on to become even more powerful (sub-960mb) over SE Canada. I’m not surprised about this rapid intensification given the more favorable changes in the upper-level pattern.

The other thing I’m noticing is a possible under-played westward extent of the precipitation shield. The late-January 2016 winter storm had a similar low intensity, tracking well SE of the 40N/70W benchmark, and look how far that system threw snow into EPA and NNJ. This is a similar setup however the axis of precipitation will be much more vertical, like the late-December 2010 system known as the “Boxing Day Blizzard.” I’m not saying that is going to happen again but it’s not that far off. Therefore as model guidance evolves into the short/meso range over the next few days, I wouldn’t be surprised to see a further westward extent of precipitation as the mesoscale algorithms pick up features that the globals struggle with.

This would likely present an elevated risk of coastal flooding for the Mid-Atlantic and especially New England. We have northerly winds on our side but a strong surface low out in the ocean pushing water/waves in.

So what does this all mean? I’m leaning towards a better chance of wintry impact for Thursday especially for ENJ. We really need to watch the live observations out west as well as the evolution of model data over the next two main cycles (tonight’s 00Z and tomorrow’s 12Z). If the current trend continues then wintry expectations will increase further. In full disclosure this system could still trend E and out to sea. We are however running out of time for that.

In English: The January 3-4 winter storm signal has been long advertised. The signal has now narrowed to mostly a Thursday, January 4 potential event. A reasonable expectation from this range are at least light snowfall accumulations, especially for coastal/ENJ regions. WNJ (both N and S) are of less concern at the moment but could be brought into light accums if ENJ trends into a more disruptive event. I would also expect possible coastal flooding and beach erosion. Whether or not the higher impact event happens is a legitimate concern now but we’re just not ready to pull the trigger yet given the complex dynamics. Tomorrow we will post our official first call snow map with detailed analysis and wildcard possibilities. In the meantime we’re doing model run-by-run analysis in the premium forum. Have a great rest of your day and please be safe! JC

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Jonathan Carr
By Jonathan Carr January 1, 2018 14:37

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