Dec 14, 2012: Three Storms Next Week

Forecast Highlights:

Following a generally inactive and mild first half of the month, some changes in the pattern are currently developing with less sustained mild temperatures, and at least in the short to medium range more storminess as well. This will be most noticeable next week with three storms expected; at this time, rain or a wintry mix is favored over a snowstorm, especially for the first two storms, but the potential is still there for at least one snow event to affect the area before the end of the month.

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Sunday - Monday: First Storm

The first storm to affect the area with the more active time frame will be on Sunday and Monday, associated with a low pressure currently in the southwestern US moving northeast towards Michigan. Currently, a moderate intensity block is located over Greenland, a feature that has been completely non-existent last year. This block will spread westward into eastern Canada, with a strong high pressure near Quebec preventing the low from continuing northeast. Instead, the original low pressure is expected to nearly stall in place while rain expands into the region. Temperatures, however, will be too warm for the area to see a snowstorm, with the only notable snow accumulations expected in central and northern New England.

Precipitation will begin to affect the area early on Sunday morning, with occasional showers lasting until the next storm arrives shortly afterwards, which will be discussed in the next section of this post. With cold air damming initially in place, the storm is expected to start out with light snow, sleet and/or freezing rain in parts of SE NY and interior SW CT; accumulations, if any, are expected to remain minimal, under 1/2 inch. Sleet and freezing rain are also possible. By the later morning hours on Sunday, with warming temperatures at the surface and aloft, precipitation will change over to rain outside of the higher elevations, with the higher elevations also changing over to rain by the afternoon. High temperatures on Sunday will range from the upper 30s in NW NJ, interior SE NY and interior southern CT, to upper 40s in NYC and Long Island. Occasional showers will continue overnight into Monday, with any freezing rain expected to stay north of the area.


Monday Night - Tuesday: Second Storm

Little separation is expected between the two storms, with occasional showers continuing until the second storm reaches the region. This one has been poorly handled by the models in the medium range, with  solutions over the last few days ranging anywhere from a heavy rainstorm, to a snowstorm, to a weak low pressure well offshore. Since then, a stronger model consensus has emerged favoring an inland track through the region, later moving east and offshore from New England. With warmer temperatures aloft expected, this will start out as rain for most of the region, with most of the frozen precipitation again staying near central and northern New England.

This storm is expected to be another rain producer for the area, only this time without the front end snow expected for the Sunday storm. Moderate rain is expected out of this one, with areas of locally heavy showers possible. Most of the rain is expected to focus on Monday night, with lighter rain for Tuesday. Temperatures on Monday and Tuesday are likely to reach the low 50s in at least parts of the immediate NYC area, with cooler temperatures elsewhere below 50 degrees.


Friday - Saturday: Third Storm

A brief break is expected in between the second and third storms, with partly cloudy skies on Wednesday and Thursday as high temperatures reach the low 40s inland and mid 40s for the rest of the area; windy conditions are likely on Wednesday behind the first storm as well. The third storm is then expected to affect the region around Friday and Saturday. Unlike the previous system, when the model guidance was all over the place several days out, there is better agreement between the models for this storm. Currently, the model guidance takes a strong low pressure towards the Great Lakes and then towards the region, with a strong cold front moving through the area followed by a much colder air mass, sticking around for at least several days. This is still a week away, however, and as the last few storms have proved, what the models are showing now may not be what actually happens with the storm, and changes are still possible over the next few days; at the same time, I do not think at this time that this is likely to be a widespread snowstorm for the area, although the current forecasts are subject to some changes. Stay tuned for more information on this storm.

Despite the medium range uncertainty, there are strong hints for a stronger surge of cold air behind this storm, sticking around for a somewhat longer period of time as well with a transient ridge near the western US. More information will be posted on the longer range over the next few days.