Jan 21, 2013: Moderate Snowstorm For Friday

**This post is from January 21, 2013. For the latest forecast, please refer to the main page.**

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Forecast Higlights:

A light snow event affected the area this evening, with up to 3-4" in isolated parts of Long Island. An arctic air mass will bring very cold temperatures tonight through Thursday, with black ice expected on wet surfaces tonight along with wind chills in the single digits to near zero throughout the day on Tuesday. The cold will continue through the rest of the week and into the weekend, with a storm potentially producing moderate snow accumulations on Friday.

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Tonight - Thursday: Very Cold, Windy

With the minor snow event moving out, the coldest air mass in 2 years is moving into the region, with 850mb temperatures near to slightly below -20 degrees Celsius through Thursday. Temperatures tonight will drop into the mid 10s to low 20s across most of the area, with low 20s in NYC. Breezy WNW/NW winds are expected tonight through Tuesday and Tuesday night, with sustained winds up to 20-25 mph. Temperatures on Wednesday will be very cold, only peaking in the upper 10s to low 20s inland and the low to mid 20s for the rest of the area. With the breezy conditions, wind chills will only be in the single digits throughout the day, dropping below zero degrees inland.

Cloud cover will partially clear on Wednesday and Thursday, when the coldest overnight lows are expected, dropping into the mid to upper 0s for interior areas and colder parts of eastern Long Island, and the upper 0s to low 10s for the rest of the area with low to mid 10s in NYC. Highs on both days will also reach the upper 10s to low 20s inland and the low to mid 20s for the rest of the area. Average highs this time of the year are generally in the mid to upper 30s.


Friday - Saturday: Moderate Snowstorm Potential

A more widespread snowstorm is expected to affect the area on Friday with the cold air mass moderating. The large scale setup is the most favorable it has been for a snowstorm in the area since early November; the model guidance continues to fluctuate north and south, although the northern solutions are becoming less frequent, with just about all models keeping the area with mostly, if not plain snow, and at this time, the storm is expected to remain as plain snow for most of the area with coastal Long Island the possible exception. The main uncertainties remain with the timing, intensity and track of the storm, ranging from the latest 0z GFS which only shows light snow, to the 0z ECM which has a major snowstorm with nearly 8-10 inches in parts of the area. Unlike the other models, the ECM shows a more amplified low pressure moving up the coast, as opposed to a relatively flat wave of low pressure shown on the GFS.

Regardless of these differences, snow is expected to fall during the day on Friday with widespread accumulations likely, regardless of whether these are minor or significant. There is still some slight uncertainty regarding the exact starting and ending times, although at this time snow is expected to develop around Friday in the early afternoon, peaking towards the late afternoon and evening hours before ending overnight. The storm is expected to move relatively quickly; at least initially, no significant precipitation amounts are expected, although should a stronger coastal low pressure develop closer to what the ECM indicates, higher precipitation amounts would be expected. There are still a few days left until the storm, and additional changes are expected in the model guidance, and a drier solution which the GFS indicates and a much snowier solution which the ECM indicates cannot be ruled out, although the potential remains for at least a 4 to 8 inch snowstorm to affect the area, with this preliminary range subject to change. The main concern at this time is for the GFS to verify, which has been consistent with its solutions of a minor event at most for the region; should this verify, the preliminary range would be revised downwards. Stay tuned for more information on this storm over the next few days.

More information will be posted with tomorrow's update on the pattern following this storm, including another round of very cold temperatures for the weekend followed by a warm up for next week.