Nov 14, 2010: Colder Temperatures To Return



***Important Note***

The NYC Area Weather final winter 2010-2011 outlook will be posted late in the coming week, which will discuss what has changed so far, the current and potential future pattern, and the potential monthly patterns. Stay tuned!

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Yesterday was a mild day across most of the area, and temperatures exceeded their forecast in places such as Long Island and southern Connecticut, where temperatures were as high as the upper 60s. Today was another nice day but a SE wind led to cooler temperatures along the coast, where Long Island/S CT had highs in the mid 50s to lower 60s, and the central/western parts of the area had highs in the lower to mid 60s.

Increasing clouds are expected for the area as a cold front stalls, which will be followed by a storm bringing rain, wind and potentially a rumble of thunder on Wednesday morning. Afterwards, a much colder pattern will start to set up for the northern United States, but it will take time until the cold can become more persistent in the area.


Tomorrow’s Outlook:

Tomorrow will be a mostly cloudy day across the area with light winds expected. An isolated shower is possible in the morning, especially north and west of NYC. High temperatures will be in the mid to upper 50s across most of the area with a few lower 60s possible in the immediate NYC area.

Looking at the rest of the region, showers are likely in the morning across parts of Pennsylvania/New York, with high temperatures in the 40s to lower 50s across most of the Northeast. Virginia will see high temperatures in the lower to mid 60s.

Tuesday – Wednesday: Storm To Bring Rain, Wind
As previously mentioned, the cold front is expected to stall near the area by tomorrow night, with a low pressure developing in the Southeast. Over the last two days, however, the models have gone through significant changes, now taking the storm into the eastern Great Lakes, keeping the heaviest rain to the west of the area while bringing through a line of rain and thunderstorms early on Wednesday morning.

The NAM model is the easternmost model, showing a significant snowstorm for the interior Northeast, however the NAM is an outlier as it is too far east and has yet to become consistent on a solution, and I expect the NAM to trend to a further west solution. The GGEM is the westernmost track, which along with the 12z GFS, brings the storm track into western Ohio. The GGEM, however, tends to take storms too far west, and I am thinking that the GFS/GGEM could trend a little more east, putting the storm track through western Pennsylvania and New York.

Forecast for the storm: On Tuesday, expect cloudy skies as the storm spreads into the area, with some showers falling in the late evening. The difference from the previous forecast, however, is that since the storm will be further west, the heavy rain will also be much further west, and instead of a steady chilly heavy rain overnight, temperatures are expected to remain steady in the overnight hours, if not slightly warm up as the cold front approaches, which would then bring heavy rain late on Tuesday night into Wednesday morning, ending before 12 PM on Wednesday. As the cold front moves through, it could also get windy after the storm exits on Wednesday evening.

If the western solutions verify, then it is possible that there could be a rumble of thunder, however at this time I am not mentioning this in the 5-Day Forecast. At least 0.5 to 1.25 inch of rain is expected across most of the area, with the higher amounts further west. In addition, windy conditions may be possible after the storm exits. Stay tuned for more details on this storm and what it may bring to the area.

Thursday – Friday: Colder Temperatures Return

Due to the storm on Wednesday being further west, it will prevent the Alberta Clipper briefly mentioned in the previous update from maintaining itself, and the models have backed off from this clipper, instead showing widespread rain/snow showers in the Northeast on Thursday into Thursday night as a trough enters the region. Thursday will likely be mostly cloudy, with high temperatures in the upper 40s to mid 50s possible across the area. Clearing skies on Thursday night along with the cold air mass will lead to low temperatures dropping into the mid to upper 20s inland, and upper 20s to mid 30s for the rest of the area.

Friday will be a colder day with mostly sunny skies, and high temperatures likely ranging from the lower 40s inland to the upper 40s in the immediate NYC area. Yesterday’s models were suggesting that 850 mb temperatures may drop t0 nearly -10c, with highs in the upper 30s to lower 40s and lows into the lower-upper 20s, however this solution is no longer likely as the air mass likely won’t be that cold.

Longer Range: Mild Start To Week, Cold Thanksgiving?

On Saturday, a weak Alberta Clipper that was previously modeled by the ECMWF model to be far south enough to bring frozen precipitation to the area is expected to track through southern Canada and enter northern Maine, bringing a cold, light-moderate snow to that area, however the weak storm will drive the trough out of the region, replacing it with a milder air mass.

There will be another cold air mass behind this weak storm, however it appears at this time that the storm may not be strong enough to pull this cold too far south, and as a result, a boundary sets up in the southern-central Northeast where temperatures are very cold north of that boundary, and south of it, including the Mid Atlantic, temperatures would be near average, if not slightly above average. This can still change though, as this is still in the medium range.

Afterwards, uncertainty increases on the models, however looking at the long range GFS and ECMWF models, another storm could form near the Great Lakes and move northeast, bringing a warmer air mass into the area and the rest of the Northeast, which would be followed by a cold front around the middle of next week to bring much colder temperatures for Thanksgiving weekend.

Up to this time frame, a -PNA is expected, or a west coast trough, which is not supportive of persistent cold in the Northeast, however according to some models, the PNA may begin to trend back to neutral, with a -NAO persisting. It is possible, however, that like the cold air originally expected for the area to move in around Thursday and persist, that the pattern may not be favorable enough, and any cold could be brief. Stay tuned for more details on this time frame and what the possible conditions for Thanksgiving weekend could be.

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