Sept 25, 2011: Another Week Of Clouds And Rain

Note: I was able to create a discussion for tonight, but due to technical difficulties, the pages were not updated tonight. By Tuesday afternoon, there should be an update in every page except for the Long Range Outlooks, which will be updated next weekend with an October/November long range outlook.

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After heavy rain on Friday, which dumped a widespread 1-2 inches of rain across the NYC area, a high pressure building into the region provided the area with a mainly cloudy yet dry weekend, with high temperatures peaking today in the upper 70s inland, lower 80s in the immediate NYC area, and the upper 70s to lower 80s in the immediate NYC area. These high temperatures are slightly above the average for this time of the year, which are approximately in the lower 70s. The low temperatures, however, had a much more remarkable departure from the average, which is also a factor contributing to a warmer than average September. In Central Park, for example, the low temperature this morning was 70 degrees while the average is 57 degrees; this is 13 degrees above the average low.

The cut off low is currently located over the western Ohio Valley, which is keeping the rain and cool temperatures to the west of the region while locking the NYC area under a warm and humid air mass. As the cut off low begins to drift east by the middle of this week, temperatures will cool down with widespread rain returning into the area by Wednesday. The cut off low will finally exit the region by Friday, but will be followed by a strong cold front which, if the latest models are correct, could bring the coldest temperatures yet this fall.

Tomorrow’s Outlook:

With the cut off low remaining to the west of the region, over the western Ohio Valley, tomorrow will be another mostly cloudy, humid and dry day with a slight risk of an isolated shower. 850 mb temperatures will be near 15-16 degrees celsius, resulting in surface temperatures reaching the upper 70s to lower 80s inland, lower 80s in the immediate NYC area, and the upper 70s to lower 80s in Long Island and southern Connecticut. A SE wind is expected.

Tuesday – Thursday: Cut Off Low Drifts East; Rain Returns

The cut off low will begin to drift to the east on Tuesday, which will bring more cloud cover and slightly cooler temperatures into the area. The rain will still stay mostly to the west of the area, however, with temperatures expected to peak in the mid 70s to the lower 80s across the area, but there should be a slightly higher risk of showers across the western half of the area.

By Wednesday and Thursday, the storm will drift far east enough to bring more widespread rain into the area. Widespread heavy rain like that of Friday is not expected, but occasional light to moderate rain is expected, which should bring an additional 1/4 to 1 inch of rain across the area. Temperatures will cool down as well, reaching the lower to upper 70s across the area.

The cut off low will merge with a storm in Canada on Friday. This will result in a strong cold air mass from Canada starting to drop south into the north central US. The storm’s cold front is expected to move through the area on Friday, keeping temperatures in the 70s while bringing another risk of showers across the area, but the entire system is finally expected to leave the region on Friday night, with clearing skies and dropping temperatures.

For next weekend, the latest models are in an agreement with showing a significantly colder air mass, with 850 mb temperatures dropping below zero degrees celsius, especially the GFS model. The GFS is likely overestimating the intensity of the cold air, showing high temperatures in the 40s across parts of the area with low temperatures in the lower 30s inland. Considering the time of the year and the GFS’ bias to overestimate cold air, this is most likely too cold, but should the latest scenario come close to verifying, the area may see high temperatures in the 50s by next weekend. Stay tuned for more information on the potential cool spell for next weekend.

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