Nov 28, 2011: Rain Returns Tomorrow Night

***Note: With the hurricane season coming to an end, the “Tropics” page has now been replaced with a “Winter” page. In this page, snow accumulation maps for days 1-3 will be posted for the region, as well as brief discussions on snowstorms and a highlight of any snow potentials in the medium range.***

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Early in the day, a cold front approached the region, bringing mostly cloudy skies across the area, but the cold front quickly retreated to the west during the afternoon and evening as expected due to a cutoff low pressure forming over the southeastern United States, bringing widespread heavy rainfall to that region with cold temperatures. There is enough cold associated with this storm that snow is even falling and accumulating in parts of southwestern Tennessee and Arkansas.

At the same time that the Southeast is seeing a wintry mix, however, the eastern US ridge persisted over the Mid Atlantic and Northeast. The model guidance from yesterday underestimated temperatures across the region by as much as 4-8 degrees, showing highs only in the lower to mid 60s in the area today. Instead, much warmer temperatures were observed, peaking in the mid 60s inland, upper 60s to lower 70s in the immediate NYC area, and the mid to upper 60s across most of Long Island and southern Connecticut. Today’s highs set new record high temperatures for this date, such as 70 degrees in Central Park and 68 degrees in Islip, and Newarks’ high of 72 degrees tied the previous record. With average highs near 50 degrees, today’s temperatures ended up as high as 20-22 degrees above average.

With the cutoff low in the Southeast starting to move northeast towards the region, tomorrow will be the last of the unusually warm days, with high temperatures again reaching the mid to upper 60s across parts of the area. After a few hours of moderate to heavy rain and thunderstorms on Tuesday night, much colder temperatures will return, but despite the cool down, temperatures will remain above the average through next week.

Tomorrow’s Outlook:

As previously mentioned, yesterday’s models underestimated the warmth the area saw today, and with the latest model guidance slowly trending warmer for tomorrow, it appears that the models may be too cold for tomorrow as well. With SE winds expected as well as increased cloud cover and scattered showers, temperatures will not be as warm as they were today, but the warmth will persist, with highs reaching the lower to mid 60s inland, mid to upper 60s in the immediate NYC area, and the lower to mid 60s across most of Long Island and southern Connecticut. If the steadier rain holds until the evening as expected, temperatures may get close to 70 degrees again in NE NJ.

The storm in the Southeast will approach the area late tonight, with scattered showers developing after at least 12 PM. A line of heavy rain in the Mid Atlantic is expected to move into places from NYC and further west around 8-10 PM tomorrow night and around 9-11 PM in Long Island/S CT, lasting through about 1-2 AM from NYC and further west, and 3-5 AM in Long Island and southern Connecticut. During this time frame, moderate to locally heavy rain will fall along with potential thunderstorms. By the time that the rain ends, at least 1/4 to 3/4 inch of rain is expected to fall across the area, with the highest amounts to the north and west of NYC.

Wednesday – Friday: Cooling Down

Behind the storms on Tuesday night, temperatures will significantly cool down on Wednesday; in comparison to the last few days, when temperatures were in the 60s and lower 70s across the area, high temperatures on Wednesday will only reach the upper 40s to lower 50s inland, lower to mid 50s in the immediate NYC area, and the mid to upper 50s in Long Island and southern Connecticut. Although these temperatures will feel colder compared to the current warmth, these temperatures are still several degrees warmer than average.

With only a weak cold air mass quickly retreating north on Thursday, high temperatures will only drop to about near average during this time frame before warming up again. Thursday will bring mostly sunny skies with slightly colder temperatures, peaking in the upper 40s inland and the lower to mid 50s across the rest of the area, but as a weak disturbance approaches the Northeast, Friday will bring increasing clouds with highs reaching the lower to mid 50s across the area. Cloud cover is expected to decrease later on Friday night as another high pressure approaches, with cold overnight lows dropping into the upper 20s to mid 30s across most of the area.

Next Weekend – Early Next Week: Still Warmer Than Average

Colder temperatures are expected to return on Saturday as the area of high pressure moves in, with high temperatures in the mid to upper 40s across the area, potentially in the lower 50s in parts of the immediate NYC area. Although these temperatures will feel much colder compared to what the area has observed recently, these temperatures are just about near the average for this time of the year, if not 1-2 degrees slightly below the average. Saturday will bring the coldest temperatures of this time frame as yet another ridge builds into the eastern US with a relatively weak low pressure affecting the Great Lakes region. Unlike the warm spells of this month, however, the ridge building in for next weekend into early next week will not be as strong as the current ridge and the previous ones throughout the month.

With 850mb temperatures warming up to about 6-8 degrees celsius, temperatures will begin to slightly warm up on Sunday, reaching the lower to mid 50s across the area. If the currently expected scenario with a low pressure near the Great Lakes on Monday verifies, Monday would bring the warmest temperatures, reaching the mid 50s across most of the area with a few upper 50s possible in the immediate NYC area. In the other scenario, which is less likely but is a possibility, the storm would be weaker with the front already over the region on Monday, which would bring a risk of showers and colder temperatures. With the low pressure near the Great Lakes bringing a cold front towards the region, there is a risk of showers between Monday night and Tuesday night.

Longer Range Overview: Behind the cold front, there is decent agreement from the models showing a strong trough dropping into the north central and then the northeastern US. Although some of the models may be overdoing the intensity and duration of this cold spell, colder temperatures are likely for the second half of next week. With some changes in the Pacific pattern, including a -EPO and +PNA developing which are more favorable for eastern US cold, a colder pattern is expected to set up between December 5 and 15, with more frequent cold temperatures and weaker/less frequent warm spells bringing the potential for slightly below average temperatures in this time frame. As I will discuss in my winter outlook in more details, however, this colder start to December is not a pattern change that will last through the rest of the month, and a warmer pattern may return towards the middle of December once again.

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