Nov 5, 2010: Mild Mid-Late Week, Longer Range Update

Note: A general outlook for the next 2 weeks has been posted in the Long Range Forecasts page. For more reasoning behind the forecast, read the discussion in the bottom of this post.

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Today was a mostly cloudy day for the area as the trough started to approach the area, with high temperatures were in the upper 40s to lower 50s inland, lower to mid 50s in the immediate NYC area, and in the mid to upper 50s in Long Island/S CT. Due to the position of the trough, the air mass was colder in the south, where reports of frozen precipitation came from places such as even Atlanta, Georgia. The trough, however, should significantly moderate, and will not be able to push much east, so the area won’t see temperatures as cold.

An isolated shower or snow shower is possible tonight and tomorrow in the northwestern parts of the area, otherwise dry conditions are expected with mostly cloudy skies. Chilly temperatures will continue through at least Monday or Tuesday, however afterwards temperatures will get much warmer.

Weekend Outlook:

Tomorrow will be a mostly cloudy day with a north to NNW wind expected. High temperatures will be in the mid to upper 40s inland and in the upper 40s to lower 50s for the rest of the area. The area will be mainly dry, other than a possible rain or snow shower in the northwestern parts of the area.

Sunday should be a nicer day with mostly to partly sunny skies. The morning temperatures will be cold, in the lower to mid 20s inland, mid 20s to lower 30s north and west of NYC and in southern Connecticut, and in the mid 30s for NYC. High temperatures will be in the mid 40s inland and the upper 40s for the rest of the area with a few lower 50s in the immediate NYC area.

Monday – Tuesday: Storm In Maine, Little Impact In NYC

During Monday, either an extra-tropical Tomas or another low pressure forming along the stalled train of moisture in the western Atlantic will become negatively tilted, and should stall somewhere near Maine, leading to heavy precipitation, some of it snow, in those areas, and while some models show rain reaching NYC, at this time I am going with a dry solution though this scenario will be watched in case it becomes more likely. High temperatures will stay chilly, in the lower 50s inland and mid 50s in the immediate NYC area.

The storm’s effects in Maine will last into Tuesday, with temperatures slightly warmer than those of Monday in the area. At this time, I am expecting partly cloudy skies for Monday, however potential changes that could be made to that forecast include increasing cloud cover and/or adding a chance of a few showers if the storm trends closer to the area.

Wednesday – Friday: Warmer, Drier Pattern Temporarily Setting Up

On Wednesday, a weak storm in the north central US will move into Canada, which will help spread a mild air mass into most of the eastern United States except for the eastern Northeast, where the cold air mass from the storm will still persist. The storm will try to pull down cold air, but will not be able to do so completely, and instead a stalled cold front over the central US will be the result on Thursday.

High temperatures in the area will rise into the lower 60s on Wednesday, with slightly warmer temperatures possible for Thursday. What will break the mild pattern, however, is a developing storm in the central US, which will set the stage for Friday and beyond.

While there is some uncertainty as this is in the longer range, the main idea at this time is that we could see a storm developing on Friday while moving NE into the northwestern Great Lakes or SE Midwest, which will push the stalled front as a cold front further east, with thunderstorms possible, potentially even some severe weather along the cold front for the central US. The storm will also pull down a colder air mass to its northwest, leading to potentially accumulating snow in its NW side. Despite uncertainty with the timing, the storm’s cold front will likely move through on either Saturday or Sunday, bringing rain and potentially thunderstorms. High temperatures on Friday will be potentially in the mid to upper 60s in the area, with Saturday or Sunday starting to cool down.

Longer Range Update: Much Colder Pattern For Northern U.S.

**As this is a long range discussion, it is important to note that the below is only speculation on the possible pattern in this time frame, as uncertainty levels in forecasts tend to increase significantly beyond the 7-day range, though there is at least some level of confidence on the overall set up such as where it is cold and warm.**

Once the storm moves out of the US, a significant pattern change will take place. A strong cold air mass will drop into the north central US, with a -AO expected. Despite this, however, a -PNA or a west coast trough is expected, with a neutral NAO, meaning that the cold spell will be focused to the west of the region, and the cold may not be able to make it all the way to the coast. The question at this time is how far east the cold air reaches, even though it is likely that the worst of it will be focused on the north central US. Other possibilities may be introduced on the models as this time frame approaches the medium range, but at this time the scenarios above are the ones shown as possibilities.

What may lead to the pattern changing, though, is a potential storm on November 17-18 that will be further east than the storms before it. There is a lot of uncertainty on where the storm track, which is expected as this is the longer range, and storm tracks can’t be nailed down to the exact location yet, but based on the pattern and the models, if the storm does happen, possibilities for this storm’s track include a coastal track off the East Coast to a storm tracking through the Ohio Valley and Northeast. Stay tuned for more details on this potential storm.

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