Feb 12, 2013: Some Snow Weds Night, Mild Friday

Forecast Highlights:

Temperatures close to average continued across the region today following yesterday morning’s rain event, with highs peaking in the low to mid 40s across the area. A storm is expected to affect the area with some snow on Wednesday night, followed by warmer temperatures briefly returning on Friday, reaching the upper 40s to low 50s in NYC. A colder weekend is expected with the potential for a storm to affect the region.



Tonight – Wednesday Night: Seasonable, Some Snow Expected

Partly cloudy skies are expected for Wednesday, with highs peaking in the upper 30s to low 40s across the area, with clouds increasing throughout the day. The next storm will affect the region late on Wednesday into the overnight hours. This storm is expected to produce snow accumulations, although there are several factors limiting how much snow falls with this system. As previously mentioned, highs are expected to be in the lower 40s on Wednesday, and there is a lack of high pressure to the north of the system resulting in marginal cold air for the storm, with this an issue especially west and southwest of NYC, where especially with the timing of the storm starting not long after temperatures peak, the storm is expected to start out with rain, despite 850mb temperatures below freezing, before changing over to snow with temperatures near to just above freezing. Slightly cooler temperatures are expected for the NYC area than locations further west where timing will be later in the evening and overnight hours, with temperatures likely near to just below freezing during the storm, although the storm may also start with a period of light rain and/or non-accumulating snow.

The next aspect of the storm to look at is the storm track; the storm is expected to track off the Mid Atlantic coast heading ENE, with the heaviest precipitation south of the area, in southern Pennsylvania/Maryland into southern New Jersey. There is some uncertainty regarding exactly how far north precipitation spreads, with the latest model guidance suggesting New York City is near the northern end of the moderate precipitation, which extends into Long Island and parts of southern Connecticut. Currently, NYC and locations east and south, extending into southern CT as well, are likely to see moderate precipitation, although this is still subject to minor north/south revisions. The amount of precipitation that falls is also an area of uncertainty; the ECM model remains dry, with little precipitation for the area which would result in mostly minimal snow accumulations. Meanwhile, the NAM remains wetter, with up to 1/2 inch of liquid equivalent precipitation just south and east of NYC. While the NAM is likely a little too wet, a bias the NAM typically displays, the ECM model is likely too dry as well. With the above taken into consideration, there is enough confidence to revise the preliminary snow forecast range downwards with today’s update.

The latest forecast is for precipitation to develop after 6-9 PM from west to east; this may start out with light rain especially from NYC and further west/southwest, perhaps for parts of Long Island as well. As temperatures cool down, a changeover to snow is expected, which will be lighter for northern and western areas while the heavier snow rates are expected towards Long Island and southeastern Connecticut. The storm will be relatively quick moving, ending by 3-6 AM across most of the area. The latest forecast accumulations have been revised downwards from yesterday’s preliminary range; totals are forecast to end up around 1 to 3 inches from NYC and further north/west, with 2 to 4 inches of snow in Long Island and southeastern CT; locally higher totals are expected for parts of the area. Should there be any additional changes in this forecast, they will be posted tonight or Wednesday morning.

Thursday – Saturday: Mild Temps Briefly Return

As previously mentioned, there is a lack of cold air for the Wednesday night storm to work with, along with a lack of high pressure to the north of the storm to provide additional cold air; following the storm, as another weak low pressure approaches the northern parts of the region, a west/SW flow will return for Thursday and Friday with temperatures warming back up to above average. Thursday is expected to be partly sunny with highs reaching the low to mid 40s inland and mid 40s for the rest of the area, with light SW winds at 5-15 mph.

Friday will be the warmest day of the week; mostly sunny skies are expected with light WSW winds and temperatures likely warmer than Thursday; at this time, I sided warmer than the operational model guidance, with highs in the upper 40s inland and upper 40s to low 50s across the area, with the warmest temperatures in the immediate NYC area (NYC, NE NJ) and further southwest; the temperature outlook is still subject to minor revisions. A weak cold front will move through overnight with very little, if any precipitation, with a NW flow returning and highs peaking in the low 40s inland and the low to mid 40s elsewhere on Saturday.

Saturday Night – Sunday: Colder; Storm Possible

Towards Saturday night into Sunday, a strong trough is expected over the eastern and central US with transient ridging over the western US. This will result in widespread cold temperatures across the eastern US, returning back to colder than average for a few days. Meanwhile, there is uncertainty regarding whether a storm takes place during the weekend. Yesterday, most of the model guidance showed some sort of a storm affecting the region except for the ECM and later runs of the GFS. Most of the models have backed further east today, with the ECM and GFS showing nothing more than scattered snow showers and cold temperatures; only the CMC model continues to show a major storm.

This is a complicated setup for the models to handle, and considering this is still several days out as well as the energy for this storm way out in the Pacific ocean with a lack of data sampling, additional changes are expected with the model guidance. Current indications suggest a mainly dry weekend aside from scattered precipitation, and for now I sided closer to this approach with the 5-day forecast, although the storm potential for Saturday night and Sunday cannot be ruled out at this time and this potential will continue to be watched. More information will be posted over the next few days.

Towards the longer range, warmer temperatures are expected towards early-mid next week with another storm likely towards Wednesday, which currently appears to develop far west enough to result in more rain as opposed to snow across the region although this is still subject to change towards a more wintry outcome for at least parts of the region, while some of the long range model guidance has been hinting at another storm possibility towards next Friday or the weekend; should these signals continue, more information will be posted as details become clearer.

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