Nov 21, 2011 Brief Update

I was unable to work on a detailed discussion for today. Tonight’s update reviews the highlights of the forecast for the upcoming week, with some hints on the longer range, and either on Tuesday or on Wednesday (likely on Tuesday) I will have a detailed write-up on the forecast, including a pattern outlook through early December. The winter outlook will be posted by the end of this month.


Tuesday – Wednesday: A strong low pressure will affect the region during this time frame, with widespread impacts ranging from heavy snow in New England to a severe weather outbreak in parts of the Mid Atlantic. This low pressure will first move towards Ohio, and will then move east through central Pennsylvania before moving towards NYC and then offshore. Occasional showers are expected during the day on Tuesday with highs in the upper 40s to lower 50s across most of the area, but as the storm approaches, rain will become steadier by Tuesday evening, with a soaking heavy rain from about 8-10 PM Tuesday night through 8 AM Wednesday. During this 12 hour period, anywhere from 1.5 to 2.5 inches of rain are expected to fall across the area, likely focusing near 2 inches. Rain Warnings and Heavy Rain Watches will be issued tomorrow afternoon for the area.

Some models have been showing the potential for temperatures to surge above 60 degrees for Wednesday morning with a risk of thunderstorms in the area. While as of yesterday evening, this solution had some support, the latest trend has been to take the storm further south, with the low pressure now modeled to end up near or south of NYC. Although some rumbles of thunder may be possible near or south of NYC, any severe weather risk will stay confined to the Mid Atlantic south of Philadelphia, where I expect to see more widespread thunderstorms along with a 15% risk of severe weather. Otherwise, temperatures will peak in the lower to mid 50s inland and in the mid to upper 50s across the rest of the area with lower 60s south of NYC. The heavy rain is expected to end by 8 AM, with the steady rain ending by at least 12 PM. Cloudy skies will continue for the rest of the day with scattered showers possible through midnight, especially focusing on the evening hours.

Thanksgiving Weekend: A much stronger ridge will build into the region, providing warming temperatures and sunshine for the long weekend. Thanksgiving day will be chilly and breezy along with mostly sunny skies, with highs peaking in the upper 40s to lower 50s across the area. Thursday night will bring mostly clear skies with lows in the lower to upper 30s across most of the area except for NYC, which should see lows in the lower 40s.

With a high pressure overhead, sunny skies are expected for Friday and Saturday with warming temperatures, reaching the mid to upper 50s across the area on Friday and the upper 50s to lower 60s on Saturday. As a cold front slowly approaches the region, increasing clouds are expected on Sunday but with dry conditions lasting along with similar temperatures compared to those of Saturday.

Next Week: There is a decent model consensus for a negatively tilted cold front to move towards the region with a wave of low pressure cutting off, forming an upper level low somewhat similar to the one we saw during late September. The negatively tilted front will move east and will likely affect the area between Monday afternoon and Tuesday. The potential may be there for heavy rain and gusty winds to affect parts of the region, including the area, and if some models verify for this time frame, thunderstorms may be possible as well. This front would then likely be followed by colder temperatures for the middle of next week, and if the right variables fall in place, a somewhat colder but not persistently cold period of time may be possible during the very end of November into early December, although the pattern will not change just yet. The update either tomorrow or on Wednesday will discuss the longer range in more details.

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