Nov 8, 2010: First Snow/Sleet Of Winter Fell Today

A coastal low pressure that was near Boston this morning, tracking towards Cape Cod by the afternoon hours, brought the first frozen precipitation, in the form of snow and sleet, to nearly all of the area today, with some light accumulations up to 1/2-1 inch being reported.

Two days ago, it became apparent that the storm would be close enough to directly affect the area, and would be able to produce snow/sleet for much of southern New England as the storm enters a cold air mass. As expected, much of southern/central New England, as well as southern Connecticut even all the way down to the coast did see snow/sleet early this morning, with some accumulations even reported. Despite the expectation of a changeover to rain once the storm reaches NYC, however, the storm went on to produce snow and sleet for the rest of the area.

The storm moved slightly faster than expected, leading precipitation to enter the immediate NYC area around 8 AM rather than 10-11 AM. In addition, the cold air mass was still present with chilly temperatures over the central/western parts of the area which remained steady in the upper 30s to lower 40s, and the precipitation was also heavier than expected, leading to temperatures dropping once precipitation started falling. The colder temperatures stayed around longer than expected, which also led to snow/sleet lasting later than expected, and with the onset of heavy precipitation, snow/sleet fell over much of northern New Jersey, SE New York, and even New York City itself!

When making my forecast map yesterday, I generally used the NAM’s snow map, as on average, the GFS tends to be too widespread with snow coverage, while the NAM is more reasonable. In this case, however, the GFS was actually correct on the snow coverage area, showing snow falling for nearly all of the area, but its problem is that it shows the snow as accumulating snow, and at one point showed 1-2 inches of snow from NNE into much of southern Connecticut.

Tomorrow’s Outlook:

Tomorrow will be a partly to mostly cloudy day for the area, with mainly cloudy skies in the eastern parts of the area and an isolated shower possible. High temperatures will be in the upper 40s to lower 50s for most of the area, except for the immediate NYC area which should be in the lower to mid 50s.

Looking at the region, rain should persist in southeastern New England as the low pressure stalls offshore, with high temperatures in the 30s and 40s in the Northeast. The Mid Atlantic should be much warmer, with highs in the lower to mid 60s in Virginia.

Outlook For Next 7 Days: Chilly, Then Warmer
As the storm stalls offshore, a NE wind is expected to persist during the week, leading to chilly temperatures as the warm air mass stays to the west of the area. High temperatures will be in the mid to potentially upper 50s on Wednesday, with Thursday slightly cooler, in the lower to mid 50s. Low temperatures on both Wednesday and Thursday night will be chilly, in the upper 20s inland, lower to mid 30s north and west of NYC, and in the upper 30s to lower 40s in NYC.

As the warmer air mass starts to spread into the area on Friday, warmer temperatures will return, into the mid to upper 50s, with a few 60s possible on Saturday as a storm approaches the Great Lakes. This storm may bring isolated showers for Sunday/Monday, but the main impact will be colder temperatures.

Long Range Outlook: Much Colder Pattern Sets Up For Northern U.S.

For the last several days, I have been mentioning the potential of arctic air becoming much more frequent in the northern U.S. in the second half of November. We are looking at a potential storm, with track ranging from an eastern Great Lakes cutter to an offshore coastal track, on November 17-19, which may interact with enough cold air to result in snow in the western side of the storm. Afterwards, as the AO and NAO become negative, there are indications that large amount of cold air may drop south from Canada and affect the northern United States during the last 2 weeks of November, including the area, starting what could be an active December for the region. Stay tuned for more details on this time frame.

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