The area of low pressure that produced over a foot of snow over central New Jersey and up to 30 inches over much of southern New Jersey and the Philadelphia metropolitan area is now in the northern Atlantic. This storm will enhance the negative NAO pattern, which will play a significant role in the development of the next threat by the middle of this week. No rest for meteorologist this month!
The next storm, which will impact the Philadelphia and New York City metropolitan area on Tuesday night through Thursday morning, is already developing to the west. Two strong disturbances, one Sub Tropical and the other Polar, are moving on a collision course over the Mississippi Valley.
Today through Tuesday morning, high pressure will dominate the northern Mid Atlantic with clear skies and cold temperatures. A strong Polar air mass will remain in place through the period with temperatures averaging slightly below normal, enhanced by the significant snow pack over the southern two thirds of the region. High pressure will slowly give way on Tuesday afternoon, but will not move east of the region. This is a key observation!
High pressure on Tuesday afternoon will reposition over the St. Lawrence River Valley back through central Canada, leading to a Cold Air Damning or CAD effect over much of the Mid Atlantic. Meanwhile, the phasing Polar and Sub
Tropical disturbances will drive an area of low pressure towards the Ohio Valley with a significant amount of Gulf of Mexico moisture once again. Due to the strong 50N/50W upper low in place, a calling card for a negative NAO pattern, this primary surface low pressure system will not be able to move much further north into the Ohio Valley. As a result, a new coastal low pressure system will become the new primary low pressure system along the North Carolina coast. There is strong agreement that this low pressure system will move northeast towards the 40N/70W bench mark, producing a significant heavy snowfall for the northern Mid Atlantic. The model guidance that seems to best handle this set up according to the HPC is the CMC or Canadian guidance seen to the left from Penn State E-Wall.
Now, there is a significant threat for a heavy snowfall from the Philadelphia metro through the New York City metropolitan area with this storm. However, I do caution that Miller B storms of this type can have some tricks up their sleeves so to speak. For example, the development of the 700 MB upper low is going to be very important in terms of where the heaviest snowfall sets up. Given that this storm will be transitioning towards the coast, the speed of transition will be a key issue as a slow transition can lead to several impacts. For, one if the primary 850 MB low is slow to transition from the Ohio Valley to the Mid Atlantic coast, more warm air advection could lead to precipitation type concerns. Also, the position of the 700 MB low will also determine not only the axis of heavy snowfall but also the dreaded dry slot that is common with these types of storms. Any shift in the actual storm track or timing of transition will have a significant impact on the forecast. However, based on the majority of guidance including ensemble guidance, there appears to be agreement that a heavy snowfall, possibly over a foot in many locations, can be expected Tuesday night through Wednesday. I would focus the worst impacts along the New Jersey coast through Long Island. The development of the 500 MB low also suggest that very strong frontogenesis and strong lifting may lead to an impressive deformation zone over the immediate coast from southwestern New Jersey through Long Island that may lead to enhanced snowfall totals as well.
High pressure will rebuild into the region with no moderation expected through the end of the week and into the weekend. Temperatures will remain below normal with highs at most in the mid 30's along the immediate southern New Jersey coast. Otherwise, most locations will remain below freezing.
Another storm threat will be possible for the end of next weekend or into early next week as the Sub Tropical jet stream remains active and the Polar jet stream supports a cold regime.
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