Jan 15, 2013: Snow, Rain, Sleet, Ice Tonight

Forecast Highlights:

The first widespread wintry precipitation event since late December will affect the region tonight, with mostly rain from NYC and further south/east and snow, sleet and freezing rain north and west of NYC, with light snow and ice accumulations. While there has not been much wintry weather in the region so far this year, winter has yet to peak; the pattern will trend colder beyond next weekend, with an increased risk of snowstorms in the long range, one of them possible early next week.

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Tonight's Storm: Final Outlook

With the storm hours away from starting, the model guidance has finally resolved the inconsistencies from yesterday's runs; this storm was not well forecast by the models, with most showing it staying well south of the area just a few days ago, but gradually trending further north and stronger with the storm as the intensity of ridging off the southeastern US coast was underestimated. This trend has been enough to bring the storm far north enough to keep the heavy snow axis north of the area again, however, as with the last two wintry events in late December, with a wintry mix expected for interior parts of the area and mostly rain for NYC and coastal areas.

The precipitation from this storm is associated with a weak, broad low pressure near the Southeast, which will move northeast towards southern New Jersey and Cape Cod. Precipitation is expected to develop by 12 AM tonight; this will be mostly rain from NYC and further south/east, perhaps starting out with a brief period of sleet, while starting out with snow north and west of NYC, mixing with sleet closer to NYC. Precipitation will continue to intensify, becoming moderate in the overnight into early morning hours. Rain will continue to fall in NYC and Long Island, while NE and north central NJ, along with portions of far SE NY, will mix with sleet, with freezing rain for some areas. Interior northwestern parts of the area, including southern CT away from the coast, will continue to see mainly snow, mixing with sleet at times towards the morning. The heavier precipitation will end towards at least 7 AM, with occasional showers persisting afterwards through the afternoon hours, mixing with sleet north and west of NYC and in southern CT away from the immediate coast.

Overall, at least 1/2 to 3/4 inch of rain is expected for NYC and Long Island, with a trace of sleet possible. For locations west of NYC, sleet and freezing rain will become involved; despite surface and 925mb temperatures near freezing, there is a warm layer between 800mb and 850mb where temperatures are above freezing for NYC and the north/west suburbs, which supports sleet, perhaps mixing with snow, changing over to rain and freezing rain for some by the morning; accumulations for the north/west suburbs of NYC, including coastal southern CT, are expected to generally range from a trace to 1 inch, locally higher further north, with up to 0.1 inch of ice possible. Interior NW areas will hold on to snow longer before mid level temperatures warm up as well, although this will take place by the time the heavier precipitation approaches its end; at least 2 to 5 inches of snow are expected, with the highest accumulations in interior SE NY and interior southern-central CT.


Thursday - Weekend: Colder, Southern Storm, Then Warmer

Temperatures will warm up on Thursday into the upper 30s to low 40s across the area ahead of an arctic cold front moving through the Northeast; meanwhile, a strong shortwave will move through the Mid Atlantic, with a low pressure approaching the Mid Atlantic. Currently, most models barely have this producing precipitation north of North Carolina; despite the current modeling, however, this is likely to adjust more to the north with precipitation, perhaps significantly north, covering the majority of Virginia and the Delmarva Peninsula, into parts of New Jersey as well, with widespread rain and some accumulating snowfall. The potential is there for this to approach the area, although at this time it is unlikely to trend far north enough to affect the area with much, if any precipitation; any impacts from this storm in the area are likely to remain minimal. More information will be posted on this over the next few days should this pose a potential to affect the area with some precipitation.

The Mid Atlantic storm will slide offshore overnight with a trough moving into the region on Friday. Overnight lows on Thursday night will drop into the 20s for most of the area and the 10s inland, with highs colder than previously thought, likely in the low 30s inland and mid 30s for the rest of the area. This trough will be short lasting, however, with a southwest flow developing on Saturday ahead of another cold front, as a weak low pressure moves through the northern Northeast. This will result in warmer temperatures for Saturday, peaking in the low to mid 40s across most of the area with mostly sunny skies. The cold front will move through the region on Sunday; while it will fail to bring precipitation into the area, it will mark the arrival of a wintry pattern which has been absent from the region this year.


Next Week: Much Colder, Snowstorm Potential

With strong ridging in the western US and eastern Pacific, a strong trough will drop into the region behind the Sunday cold front, with much colder temperatures entering the region for the first time this winter. Highs will return into the 30s and possibly the upper 20s on Monday, with lows in the 10s inland and 20s for most of the area. The initial surge of cold air will be short lived, however, as a weak clipper system moves through the Great Lakes and into the region. This is still a week out and is subject to change, although the potential is there for this to redevelop as a stronger low pressure off the coast, with a snowstorm possible for the region, including the NYC area. Stay tuned for more information on this potential, as well as the longer range pattern through early February, with the next pattern outlook later this week.