Most of the Northeast saw another below-average day as the Arctic high pressure system that has been dominating our weather over the past few days has finally begun to head off to the east over portions of southern Canada. As this high pressure system retreated to the east, we saw wind direction flip to a more easterly/northeasterly, with winds in the mid levels becoming more southwesterly ahead of a large disturbance moving south over the Great Lakes region. These southwesterly winds have aided in providing a slightly warmer airmass aloft, with some weak moisture also working into the low to middle levels of the atmosphere. This allowed the development of some mid to upper level clouds over the Mid Atlantic and Northeast during the afternoon hours, with even some scattered flurries being reported within in a weak band of moisture over portions of Pennsylvania. The combination of slightly warmer mid levels, partly cloudy conditions, and easterly low level flow made for slightly warmer highs when comparing them to the past two days. The immediate NYC metro area saw readings in the upper 20’s to lower 30’s, with locations to the north and wets seeing temperatures in the lower to middle 20’s, which is still around five or so degrees below normal. Generally dry and calm conditions are expected for the rest of the evening and into the overnight hours, with a slight chance of some widely scattered flurries. Temperatures will likely fall back into the lower to middle 20’s across the immediate NYC metro area, with teens expected to the north and west.
Light-Moderate Snow Event Likely Tuesday Into Wednesday
This afternoons model guidance has come into slightly better agreement regarding a large closed upper level low centered over the Great Lakes region this evening. This upper level low has been meandering in about the same position for the past 36 hours or so, but this will change tomorrow afternoon as an impressive Pacific disturbance crashes into the West coast. This disturbance will act as a “kicker” for the upper level low in the Great Lakes, and cause it to elongate while becoming positively tilted. As it does so, a large upper level jet will extend from the Southeast Unites States and into the Northeast. Some weak moisture will be involved in this initial setup, allowing for snow to break out just ahead of a frontal system as the upper level jet provides some adequate lift along the front. This frontal system will be located over the eastern third of the country by tomorrow afternoon, with snow likely forming over much of the Mid Atlantic and Northeast during the late morning and early afternoon hours. Some light snow may work its way into the NYC metro area later in the afternoon, but there may be some rain mixed in closer to the coast as surface temperatures hover at or above freezing.
A weak surface front associated with some more robust moisture from the Atlantic will begin to develop off the Mid Atlantic coast during the late afternoon hours and into the evening on Tuesday. This afternoons models have shown more of the moisture becoming super-imposed with the upper level jet streak aloft, which allows a very weak coastal low to develop off of the Delmarva peninsula by 8-10pm tomorrow night. Depending on the track of this low and the associated moisture plume, we could see more moderate snow develop over eastern PA, MD, VA, SNY, eastern NJ and Connecticut during the overnight hours. Again, precip type may be more wet than white closer to the coast, but we could see a gradual shift to snow during the morning commute for locations to the south and east of NYC. This weak low pressure system will be moving at pretty good clip, so as of now we expect that snow will peak in intensity over the NYC area right around 7-9am before very gradually tapering off from west to east during the afternoon. At this time, we expect generally light accumulations to the south of Northern NJ, with light to moderate accumulations further off to the north and east.
There are some uncertainties that remain with this system, as surface temperatures during the height of the storm may be a little too warm for accumulating snow, and this would cause totals to decrease a bit, especially to the south. Another possibility is that we see the coastal low develop a little quicker than originally thought, which would not only brings in more moisture, but would drag more cold air in from the north. Such a solution would yield higher snow amounts area-wide, but at this time we feel that solution is less likely to happen. However, we will be closely monitoring this system over the next day or so, so make sure to check back for future updates!
Have a great night!