Oct 9, 2011: Rain Returns This Week

As a strong ridge moved over the region, mostly sunny skies were observed, and the warm air mass in place, with 850 mb temperatures as high as 16-17 degrees celsius, brought record breaking high temperatures across parts of the area. Temperatures peaked in the mid 80s inland, mid to upper 80s in the immediate NYC area, and the upper 70s to lower 80s across most of Long Island and southern Connecticut with mid 80s closer to NYC. Notable high temperatures across the area include a high of 87 degrees in Teterboro, NJ and JFK airport, and a high of 88 degrees in Newark. These temperatures are nearly 20 degrees above the average for this time of the year; the NYC area has not seen October temperatures this warm since the fall of 2007.

With the ridge staying over the region, tomorrow will bring similar temperatures to those of today, with parts of the immediate NYC area once again reaching or breaking the 85 degree mark. Colder temperatures will return by Tuesday and Wednesday, however, as the ridge weakens and a subtropical disturbance moves in from the south, bringing widespread rain across the region for the second half of this week, exceeding 1-2 inches in some areas.

Tomorrow’s Outlook:

With the warm air mass slightly weakening and shifting further south, tomorrow will bring temperatures similar to, if not slightly cooler than those of today. With a NW wind, high temperatures will peak in the upper 70s to lower 80s inland, lower to mid 80s in the immediate NYC area, and the upper 70s across most of Long Island and southern Connecticut.

Tuesday – Friday: Rain, Colder Temperatures Return

The high pressure that was stationary over the region over the last four days will begin to weaken tomorrow and on Tuesday. As it weakens, a subtropical disturbance currently near the eastern coast of Florida will move into the southeastern United States, and from there will be able to move up the coast. As a result, Tuesday will be the last of the mainly sunny and dry days. Temperatures will cool down across the area compared to tomorrow’s temperatures but will remain above average, reaching the mid to upper 70s from NYC and further west and the lower to mid 70s east of NYC.

By Tuesday night, mostly cloudy skies will spread into the area from south as the subtropical disturbance approaches. Mainly cloudy skies are expected during the day on Wednesday as rain spreads in from the south, starting to affect the area around the late morning or early afternoon. Due to the cloud cover and rain, Wednesday will bring colder temperatures, peaking in the mid 60s across most of the area, higher in the immediate NYC area and lower near the coastal areas and further inland. The rain will intensify late during the day, with moderate to locally heavy rain expected during the evening and the first part of the overnight hours. By the time that the first round of rain ends on Thursday morning, at least 1/2 to 1.5 inch of rain is expected across the area.

The departing wave of rain will leave behind cloudy skies with scattered showers for Thursday and Thursday night across the area. Meanwhile, a warmer air mass will move into the region, bringing high temperatures into the upper 60s to lower 70s across the area. By Thursday night, the storm that will affect the area on Wednesday night will interact with a Canadian storm, and the Canadian low pressure will move into the Great Lakes while intensifying and becoming negatively tilted. The storm’s cold front will then move through the region on Friday, bringing showers across the area, and thunderstorms may be possible as well. The rain is expected to end by Friday night as drier conditions return and the winds begin to incease. Stay tuned for more information on the stormy weather for the second half of this week.

Next Weekend: Colder, Then Warming Up Again

Behind the cold front on Friday, a colder air mass will move into the region as the low pressure briefly stalls near the northern Great Lakes. This will not be a strong cold air mass, but will be strong enough to keep high temperatures in the lower to mid 60s across the area, with low temperatures in the mid 40s to mid 50s across the area. With the intensity of the low pressure, windy conditions are expected across the area on Friday evening and again on Saturday, with gusty winds expected across the area. As the trough begins to weaken, temperatures will slightly warm up around Sunday.

As mentioned over the last several days, this will not be a sustained cold spell, and with a -PNA and +NAO pattern expected to continue, another ridge should spread into the region by early next week, likely bringing above average temperatures once again. This ridge, however, should not be as strong and as long lasting as the current ridge. There is more uncertainty afterwards due to the time range, but this weaker warm spell may be a step towards more frequent colder temperatures affecting the northern US, potentially including the area, during the last 7-10 days of October. More information will be posted on the longer range with the daily updates.

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