Mar 20, 2011: Snow, Sleet Tomorrow Morning

***This post is from 2011. Please visit the MAIN PAGE to see the latest forecasts for the NYC area.


Today brought mainly sunny skies to the area as a high pressure moved through the region, with temperatures similar to those of yesterday. Cloud cover is increasing as the next storm is moving in, but unlike most of this month’s storms, however, this one will produce frozen precipitation north and west of NYC, with the potential for up to 1-2 inches of snow and sleet in Sussex and Orange counties by tomorrow morning. This is not the last of the snow possibilities, however, as yet another storm on Wednesday may bring frozen precipitation to parts of the area.

Tomorrow’s Outlook: Snow, Sleet To Rain

The cold air mass that has been over the area for the last few days is now moving out as a storm affecting the Great Lakes is moving east, expected to move through the Northeast tomorrow and towards Maine tomorrow night. There will be enough cold air ahead of the storm to result in frozen precipitation especially north and west of NYC, and as a result, once precipitation moves in between 3 and 6 AM west of NYC, it will fall in the form of snow for northern NJ and interior SE NY. 850 mb temperatures will also be below freezing for NYC and Long Island when precipitation starts, however due to warm surface temperatures, rain is expected to fall in these areas.

A burst of moderate snow is possible in the northwestern parts of the area tomorrow morning, especially towards Sussex and Orange counties, which will then change over to sleet, followed by a changeover to rain. The storm will be quick to move out, ending west of NYC by noon-2 PM. By the time that the storm ends, at least 1 to 2 inches of snow and sleet are expected in parts of Sussex and Orange counties, and I issued a Light Snow Alert for these areas as a result.

For southern Connecticut, precipitation will begin in the morning hours and intensify by the early afternoon. Despite 850 mb temperatures below freezing when the heaviest precipitation falls, it will do so during the afternoon with warm surface temperatures, and precipitation type by then will most likely be rain. The storm will end by the late afternoon.

Wednesday – Thursday: Snow Or Rain?
Today’s models continued to show a snowstorm potential for the area, with the biggest risk of such an event coming from the GGEM model, showing heavy snow for northern New Jersey, and the NAM model, which keeps most of the snow south of NYC but eventually brings moderate snow into parts of the area. The majority of the models, including the UKMET and the 12z ECMWF, also show a mainly snow event for the area, however the GFS remains with a northern solution, showing mostly rain for NYC. While I think that the GFS is having issues handling the storm, I continue to expect this storm to produce mainly rain for NYC.
The models have continued to trend north from yesterday, with the GGEM previously showing the heaviest snow south of northern NJ now showing the heaviest snow over NJ, the GFS which had a mainly rain for NYC trending even more north with today’s runs, and the UKMET trended north as well. The only model that did not trend north was the ECMWF, which had rain for the area in its 00z run but trended south in its 12z run. The ensemble means of the GFS, GGEM and ECMWF are still north of their operational runs, and while I do not think that the storm tracks north of NYC, at the same time I do not think that it will track south of the Delmarva Peninsula.
The GFS continues to show a rain event for the area, however its last few runs have not been very consistent, with its 18z run showing a norlun trough for the Northeast which no other model shows. It is also drier than the other models. Regardless of whether it is correct or not with its rainy solution for the area, the GFS is most likely not done trending yet, and additional changes are likely with its solutions tomorrow.
Storm’s impact in NYC Area: Overall, my thoughts have not changed since yesterday on how the storm affects the area, expecting the best risk of moderate snowfall in the area well north of NYC. The storm may start out on Wednesday morning with snow especially north and west of NYC with light accumulations possible, however the main part of the storm will likely be rain. Should this scenario verify, the rain in NYC would last until at least 2-4 AM on Wednesday night with amounts between 1/2 to as much as potentially 1 inch possible, and the rain may mix with and change over to snow in northern NJ as the storm ends.
The main model consensus still shows a mix/snow storm for the area, and even though I expect this consensus to shift north at this time, it is still a possibility that we see a further south and cold storm that would bring a moderate snowstorm to places such as northern New Jersey. At this time, such a scenario is unlikely, however it will be watched in case it becomes more likely. Stay tuned for more information on this storm.
Longer Range: Beyond this storm, a much colder air mass will result in below average temperatures for Friday and the weekend, with high temperatures struggling to reach the 40 degree mark in NYC and staying in the 30s inland, and low temperatures even dropping into the 10s for the interior parts of the area. The next storm is expected to affect the area around Monday, 3/28.

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