January 11-12, 2011 Storm Summary

The winter of 2010-2011so far has exceeded its expectations, producing more cold and snow than expected, including one of the biggest snowstorms on record for New York City on December 26-27, 2010. This time, New York City was spared from the heaviest snowfall, as the storm produced widespread 15-30 inches of snow for New England, however it was still enough for widespread heavy snow to affect the area, bringing this winter’s snow totals above average for most of the area in only half of the winter.

Forecasting The Storm:

While forecasting this storm was easier than the December 26-27 storm, when all of the models caught on to the big snowstorm idea only one day before the storm, there were still some difficulties forecasting the storm, especially in the shorter range. It appeared that there was the potential for a storm to affect the area since early January, when it was first mentioned in my updated winter outlook. Later on, as it became apparent that the storm would affect the area, I discussed it in more details.

With this storm, there was a higher than usual confidence in the medium range that it would affect the area with snow. A set up with a primary low to the west and another one to the south suggested that even if the main coastal low misses the area, it will still bring at least some snow, supporting my decision to put certain snow in my forecast 4 days prior to the storm. By then, however, a split set up between the models that lasted until the day before the storm.

The global models, such as the GFS, GGEM and UKMET, were consistently east with the storm and showed much lighter QPF maximums, bringing barely 2-4 inches of snow to the area and sparing New England of most of the heavy snow. The NAM and the short range models, however, showed a further west and wetter scenario than the global models. The short range models typically handle this type of an event better, and we also had a similar case with the 12/26 blizzard where even on the day before the storm, the GGEM and UKMET were still too far east, therefore I used the western solutions, especially the NAM for my forecasts.

Two days before the storm, the NAM trended significantly wetter, highlighting the potential of as much as 2 feet of snow in southern New England. Even though it did not have much support from other models, the short range models also had the idea of high precipitation totals, and I included this potential in my snow map, as well as a widespread 15+ inch area from Long Island into southern New England. The majority of southern New England ended up seeing over 15-20 inches of snow with amounts locally as high as 30-35 inches of snow. In my January 8 update, I mentioned the potential of 8 to 14 inches of snow for the immediate NYC area, and kept that forecast the same with only minor changes. On the day that the storm started, the GFS, GGEM and UKMET models finally caught on to the expected scenario, showing a much further west solution.

Storm History:

**The radar image to the left shows the storm as the coastal low began taking over as the main storm, around 11 PM.**

Prior to reaching the area, the storm also had a significant impact in other parts of the US. In the southern United States, it moved from west to east near the coast of the Gulf of Mexico, producing a significant ice and snow storm, resulting in snow cover in every US state except for Florida. As the coastal low lost most of its heavier precipitation once reaching Florida and the Carolinas, another weak low pressure became the primary low further north. This primary low then moved northeast, reaching Ohio, while producing a large area of moderate to heavy snow moving east through Pennsylvania.

While the radar appearance of the coastal low was rather unimpressive on Tuesday afternoon, things quickly began to change by the evening. The coastal low started to intensify faster, becoming the main storm, and as the snow entered the area from the west, the direction in which the precipitation came from changed from west to south as the coastal low continued to organize. Widespread heavy snow developed in New Jersey with rain and thunderstorms near the immediate coast, moving northeast to affect the area. Through the early to mid overnight hours, heavy snow continued to affect the area with snow rates generally between 1 and 2 inches per hour, lower in some places and higher in others.

The snow was quick to end for places west of NYC, already moving out with sunshine by the morning hours. For places east of NYC, however, it was a different story. As the low pressure quickly intensified, it moved over eastern Long Island, with a heavy deformation snow band affecting central Long Island and western Connecticut, and thundersnow was also observed. The storm then slowed down near the coast of Massachusetts while producing lighter snowfall for the eastern parts of the area through the afternoon hours. By the evening, most of the area was dry.

Storm’s Aftermath:

**A map showing the estimated final snow totals will be posted soon.**

The storm brought widespread wintry precipitation from the southern and central United States into most of the eastern United States, however the worst of the storm focused on New England. Heavy snow with blizzard conditions and thundersnow was observed there, and snow continued through most of January 12th as the storm significantly slowed down off the coast of Massachusetts. Snow totals across most of southern and central New England were over 15 inches with 20+ inch reports also widespread.

In the area, the heaviest snowfall ended up in southern Connecticut, where the heaviest banding set up. Snow totals ended up over 15 inches for almost all of southern Connecticut, with 20+ inch reports also widespread. The biggest reported snow total in the area was 30.5 inches in North Haven. Long Island saw more of a contrast between the lighter and the heavier snowfall, with amounts anywhere from 6 to 18 inches and the heavier amounts focusing on Suffolk county, where there was a report of 18.6 inches in Farmingville. Lighter snow totals were reported further west, with New York City reporting anywhere from 6 to 12 inches of snow and northern New Jersey reporting 5 to 10 inches of snow.

While this storm was not a historic snowstorm in the immediate New York City area, having more significant impacts in southern Connecticut into New England, it was yet another significant snowstorm of a snowy winter for the area, bringing snowfall above the average for the entire winter in most of the area.

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