Jan 16, 2012: Three Snow Potentials Ahead

9:40 PM Update: Widespread light to moderate snow, mixing with sleet at times, is now falling across northern New Jersey, with moderate snow in SE NY and interior southern Connecticut along with a light rain/snow mix in NYC. A widespread dusting to a coating of snow has been reported in places where snow/sleet is falling, although further inland towards interior SE NY, up to 1/2 inch of snow and sleet has been observed in some cases.

The wintry mix will continue to affect northern NJ and SE NY through at least 10:30 to 11 PM, when a dry slot from Pennsylvania will begin to move in. Until that time, an additional coating to 1/2 inch of snow is expected in interior SE NY and southern CT, with more light snow and sleet on top of the coating observed elsewhere in N NJ and SE NY. Once this round of precipitation ends, temperatures aloft will begin to warm, with the next round of precipitation coming in later tonight falling as rain in most of the area and freezing rain in NW NJ/SE NY.



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The cold air mass that was over the region through last night began to move out, with mostly sunny skies for today along with warmer temperatures, reaching the lower 30s inland, lower to mid 30s in the immediate NYC area, and the mid to upper 30s in Long Island and southern CT. As the radar shows to the left, there is precipitation approaching the area; this precipitation, however, will not start out as rain for most places north and west of NYC; read below for more information on the approaching snow/sleet.


The winter so far has only featured a handful of isolated snow shower events for the area, and while a cold and snowy pattern is not unfolding, there are three potentials for some frozen precipitation to fall across the area; the first is tonight, with widespread sleet from NYC and further north/west this evening before transitioning to rain, with freezing rain towards NW NJ and interior SE NY. In addition to tonight, a weak clipper on Thursday night along with another low pressure on Saturday will bring two additional snow possibilities, although very marginal, to the area.


Tonight - Tuesday Night: Snow/Sleet Tonight, Rain Tomorrow

Temperatures aloft at 850mb have warmed up above freezing across most places west of NYC, meaning that snow is not expected to fall across most of the area except for interior southern Connecticut late tonight. The 925mb layer closer to the surface, however, is decently below freezing, with surface temperatures still near freezing across most places north and west of NYC. Dew points, in addition, are still colder than the surface temperatures, and when the storm moves in around 8-9 PM tonight, evaporative cooling will take place, which along with a small pocket of sub-freezing 850mb temperatures moving in, will allow for widespread light sleet, mixing with light snow, to fall in SE NY, northern NJ and even NYC between 8 PM and 12 AM. Up to a coating of sleet is expected outside of NYC, possibly up to 1/2 inch further north, although the sleet is expected to change over to light rain across the immediate NYC area and southern Connecticut by 12 AM.

By 1-2 AM, temperatures will begin to slowly warm up across the area. surface temperature in NW NJ and Orange County in NY, however, will remain below freezing, setting up for a freezing rain event. Although no significant amounts of freezing rain are expected, with up to 0.1 inch at most, the freezing rain is expected to remain light, making it easier for the rain to freeze on most surfaces and creating hazardous travel conditions. The freezing rain inland is also expected to change over to rain by Tuesday morning.

A break from the rain is likely around Tuesday morning, with a few breaks in the cloud cover possible. By Tuesday afternoon, however, moderate rain will move into the area, lasting through the evening, as temperatures steadily rise into the mid 40s from NYC and further west and the mid to upper 40s in Long Island and southern CT. Temperatures will remain steady until about 12 AM along with isolated showers, with the storm's cold front moving through the area overnight. Temperatures will drop into the 30s towards Wednesday morning along with increasing winds, gusting up to 30-40 mph at times.


Wednesday - Thursday: Colder, Some Snow Thursday Night


Behind the cold front, cooler temperatures are expected for Wednesday, reaching the upper 30s to lower 40s across most of the area with winds still gusting up to 30-40 mph, especially in the morning. Clearing skies are expected overnight as a high pressure moves towards the region, with temperatures dropping into the mid 10s to lower 20s for most places north and west of NYC, with low to mid 20s expected for Wednesday night in NYC and parts of Long Island.

Temperatures will warm up into the mid 30s for Thursday, however increasing clouds are expected as a weak low pressure approaches from the west. Most of today's models have increased the amount of precipitation that falls with this clipper, with the GFS and CMC showing nearly a tenth of an inch of precipitation, which combined with temperatures in the 20s, would result in up to an inch of snow in parts of the area. There appears to be potential redevelopment of the clipper offshore, although there is some uncertainty with this scenario; if it does happen, snow could be enhanced over Long Island with over 0.1" of liquid-equivalent precipitation. The other scenario for this storm is where the clipper is further north, and the majority of the region sees snow except for NYC, which would end up under a dry slot with snow falling to the west and east. Last night's GFS runs as well as the 12z ECM support this scenario. There is still uncertainty, although the potential for snow in parts of the area is increasing, and I placed widespread scattered snow showers across the area in the 5-Day Forecast page, focusing over Long Island. Accumulations are still uncertain, although if the first scenario mentioned verifies, supported by the CMC and GFS, up to an inch of snow may be possible in parts of the area, especially east of NYC. Although this is nothing close to a significant snow event, it has the potential to become the first accumulating snow event for parts of the area. Stay tuned for more information on Thursday night's snow potential.


Friday - Sunday: Warming Up, Some Rain/Snow Possible


Behind Thursday night's storm, a slightly colder air mass will move in, with temperatures once again reaching the mid 30s for highs across most of the area on Friday. Meanwhile, an area of snow is expected to move towards the Great Lakes, with a low pressure moving through the region towards Saturday. Yesterday's models had different solutions, although today's models began to hint on a possible snow event, with the latest 18z GFS as well as both of today's ECM runs showing light snow accumulations for parts of the area. The ECM, however, has shown snowstorms for the area in its medium range several times this winter before losing them as it enters the shorter range, and most storms in the medium range this winter trended north and/or west as they approached the shorter range. The GFS and ECM runs this afternoon already began to trend north, and given the pattern and trends, I expect the storm to trend north of its current position on the models. With cold air ahead of the storm, light snow is possible again in parts of the area, and due to uncertainty, I went with a rain/snow mix across the area, changing over to rain in parts of the area if the warmer scenario verifies. There is still some uncertainty on Saturday's storm potential, however, and it is possible that the storm ends up further south to result in a light snow event, or it could trend north to bring rain for the area with snow again falling in New England. More information will be posted on this potential event as details become clearer.

Looking at the longer range, the addition of the Saturday event along with colder air than previously expected in southeastern Canada is decreasing the probability of a major warm spell across the region; despite this, however, the potential is still there for an unseasonably warm day or two next week. Although some more cold than previously expected is likely for next week, temperatures overall are still likely to average out to warmer than average. Stay tuned for more long range updates, along with updates on the pattern potentially setting up for February.