Dec 24, 2012: Two Storms, Then Cold

Forecast Highlights:

A weak and fast moving light snow event affected the region tonight, with less than 1 inch of snow for most of the area, locally higher, with more snow than expected in NYC and Long Island. With the minor accumulations, enough snow will remain on the ground for some to experience a white Christmas. This is just the first storm of this new wintry pattern, however, as a significant storm on Wednesday produces heavy rain, wind as well as snow and ice inland, followed by another storm potential next weekend.

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NOTICE: Pattern outlook #7 was posted today. This can be found below this post and the storm updates from this evening.

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Wednesday - Thursday: Heavy Rain, Wind, Snow, Ice

Behind tonight's storm, dry conditions will briefly return for Tuesday and early Wednesday with highs on Tuesday reaching the upper 30s to mid 40s, likely melting most, if not all of the snow that accumulated tonight, although for some it is likely to stay on the ground long enough to allow for a white Christmas. The next storm will quickly move in, however, and will be stronger and larger, with varying impacts across the region including heavy rain, snow, wind and ice.

With last night's forecast, I continued to expect a track near the Interstate 95 corridor, with the potential for front end snow and wintry mix for the interior parts of the area. Today's models have trended colder with the storm with a slightly southeast track, and some show several inches of snow not far to the northwest of NYC, while keeping NW NJ and interior SE NY with over 6 inches of mostly snow. For now, I am keeping my forecast mostly the same from yesterday, although should this trend continue, the forecast will likely be revised tomorrow to a slightly cooler one.

To the left, I re-posted my preliminary scenario map as other than some differences, such as the south end of the plain snow zone as well as the axis of heavy snow in the Ohio Valley, which will be changed with tomorrow's final scenario map, it remains generally valid for tonight's forecast. The gray zone is for plain snow, with the pink zone representing snow to ice/rain, where accumulations are expected, significant for some areas.

For the NYC area, precipitation is expected to develop after at least 4-6 PM. This will be in the form of rain south and east of NYC, with a few front end snow showers possible for NYC. North and west of NYC and in southern Connecticut, some light snow is expected for the northwest suburbs with at least up to an inch possible, followed by a changeover to rain. The rain will then become heavy into the evening and early overnight hours, along with windy conditions with gusts above 40-45 mph possible. For interior parts of the area in NW NJ and interior SE NY, a much more wintry event is expected. Snow will develop in the afternoon with moderate accumulations expected by the early overnight hours. As the secondary low makes its way towards NYC and temperatures aloft warm up, freezing rain and sleet are expected, gradually changing to light rain as the storm ends. Most of the area should be dry by early Thursday morning. For more localized forecasts, check the latest 5-Day Forecast.

Significant impacts are expected from this storm across the region. From NYC and further south and east, heavy rain up to 1-2 inches is expected along with wind gusts above 40-45 mph. North and west of NYC, front end snow is expected, with moderate snow accumulations expected towards NW NJ and interior SE NY, potentially between 4-8 inches. Ice is also expected to become involved with freezing rain likely for interior parts of the area as well. As previously mentioned, however, there is still the possibility the storm could be slightly cooler than expected; if this is the case, interior SE NY would remain with mostly snow, with minor accumulations of at least 1-3 inches extending into the north/west suburbs of NYC as well. Stay tuned for a final storm forecast with Tuesday's update.


Next Weekend: Snowstorm Potential

Drier conditions will return for Thursday and Friday, with breezy winds and temperatures generally in the mid 30s to low 40s. The active pattern continues through next weekend, however, with another storm potential for the region. As today's long range pattern outlook mentioned, a rising PNA is expected in this time period, while the mid week storm ends up near Newfoundland. This sets up for a coastal low pressure to develop and affect at least parts of the region. At this time, the model guidance is mostly to the east of the area, some well to the east, with the GFS showing a weak snowstorm but with the heaviest snow offshore. What the models show in the medium range is not final, however, as seen with the mid week storm when this far out, some models such as the GFS were showing a snowstorm in NYC. At this time, I expect the model guidance to trend west, but how far west is still uncertain. This storm is not expected to end up far west enough to produce another mild rain event for the region, with the main possibilities at this time ranging from an offshore storm to a significant nor'easter. It is still too far out to determine how much snow falls, if any, and a solution close to today's models with the snow mostly to the east of the area is possible, although the potential is there for a snowstorm, potentially significant, to affect the region, possibly including the area, in this time period. Stay tuned for more information on this storm potential as details become clearer.