Mar 23-24, 2011 Storm Updates

Below, storm updates will be posted on the major late season snowstorm currently affecting the area.

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8:35 PM: Storm Already Ending

After I made my previous update, the second round in Pennsylvania began sliding east southeast, and from the latest observations, it is clear that places north of the NJ/NY border and southern Connecticut will fail to see any significant precipitation tonight. The second round of the storm is currently affecting most of the area, bringing heavy sleet and thundersnow for northern New Jersey and even in NYC. Looking at the radar loop, however, the northern end of the precipitation in eastern PA is slowly shifting south, not moving east like originally expected.

The storm has already ended for northern Sussex county and most of Orange county for the main part, with some more snow showers expected but no additional moderate-heavy precipitation. Over the next 1-2 hours, precipitation will slowly begin to weaken north of I-80 in northern New Jersey while mixing with and changing over to snow, though additional moderate to heavy sleet will continue in NYC for at least the next 2-4 hours. Steady precipitation will also begin to end in southern Connecticut over the next hour or so.

This is the last update for tonight. The next full update will be posted tomorrow, discussing the unseasonably cold air expected to affect the area through the weekend and early next week and whether any additional snow may fall.

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6:30 PM: Second Round Approaches, But More Rain Than Snow?

The widespread severe thunderstorms in the Ohio Valley have recently moved into Pennsylvania, but are beginning to become less severe and more of a widespread area of heavy rain and thunder. Some thunder has even been observed west of NYC along with the sleet. This round of the storm is moving rather quickly and is well south of where it was modeled to be last night, with the northern edge expected to only reach southern New England. The problem, however, is that temperatures are marginal at best for the immediate NYC area, where rain and sleet is currently falling.

With the latest observations, it is clear that the area will see some sort of moderate-heavy precipitation out of this second round, but in what form it falls is the question. It appears at this time that temperatures may be warm enough that New York City and places south of Interstate 80 see mainly rain out of this second round, followed by back end snow/sleet with no accumulation in NYC and perhaps a little accumulation towards I-80 in New Jersey. Places towards southern Westchester, and eastern NE New Jersey should see more of a rain/snow/sleet mix changing over to snow at the end, with accumulations generally less than an inch, and places such as southern Connecticut, the rest of northern New Jersey and southeastern New York seeing mostly, if not plain snow with accumulations between 1 to as much as 4 inches expected.

The storm will be quick to move out, and is expected to begin ending after 12-2 AM from west to east. By the morning, other than a few snow showers, dry conditions are expected. Stay tuned for more updates this evening on the second round of this storm.

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3:25 PM: This morning, as the storm moved in, snow fell across the entire area, however a band of heavy snow unexpectedly set up from northern New Jersey into NYC, resulting in accumulations already as high as 5-8 inches in the higher elevations of northern New Jersey this morning! Snow continued to fall throughout today, and is currently mixing with sleet especially in the immediate NYC area and further south/east.

We are currently seeing a very interesting set up with the storm. While snow is falling in the New York City area, Chicago has been seeing plain rain, temperatures in southwestern Pennsylvania and central Ohio have even reached the 70 degree mark, and a major severe weather outbreak is currently ongoing in parts of the Ohio Valley. While with such a set up, it would be easy to think that the warmth will easily push into New York City with mild temperatures, the storm is blocked from going east and doing so, and will be forced to slide east southeast later tonight, keeping the area in the cold sector of the storm and keeping places north of NYC such as Rockland and northern Westchester counties with mostly snow.

Tonight’s Forecast: Through the evening hours, occasional snow and sleet are expected to continue across the area with light accumulations possible inland and no accumulations in the immediate NYC area and further east. What happens overnight, however, is still slightly uncertain, with several possibilities for tonight’s round. The thunderstorms currently in the Ohio Valley will eventually move east and affect the region, not with thunderstorms but with additional widespread precipitation, but the latest models are split on how this affects the area.

With the current observations, it is unlikely that this is a mainly rain storm for New York City and NE NJ, with the northern scenarios such as the NAM, RGEM and HRRR showing moderate to potentially heavy snow for tonight with as much as 2-5″ for parts of the immediate NYC area and higher accumulations to the northwest of NYC, and the southern scenarios including the UKMET, RUC and ECMWF showing the storm mostly to the south of the area with barely additional 0.2″ QPF falling in the form of snow, which would have difficulties accumulating.

At this time, I am expecting a mix to continue through this evening with snow becoming more widespread later tonight before ending, with little to no accumulations in NYC and up to 1-4 inches north and west of NYC possible, however this is still uncertain and is subject to changes. Updates later today will discuss this in more details.

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