Sept 1, 2011: Pattern Becomes Active Again

Note: The 5-Day Forecast page was not updated tonight, but will be updated either on Friday morning or afternoon.


A high pressure stuck over region provided another nice day across the region as the tri-state area continues the clean up from Hurricane Irene. The high pressure will continue to provide nice weather tomorrow, but as the high pressure exits the region this weekend, the pattern will become active once again as a low pressure brings 90 degree heat, the potential for severe weather on Sunday and Monday, followed by significant uncertainty for next week regarding a new tropical depression in the Gulf of Mexico and Tropical Storm Katia.

Tomorrow’s Outlook:

As Invest 94L in the western Atlantic starts to drift away from the region, southeast winds are expected to continue over the area along with partly cloudy skies. Temperatures are expected to peak in the mid to upper 70s inland, upper 70s to lower 80s in the immediate NYC area, and the mid to upper 70s in Long Island and southern Connecticut.

Weekend Outlook: Heat, Humidity Make A Return

Even though August has ended and fall is approaching, summer will make a brief appearance in the area this weekend. A strong surge of heat in the Great Lakes, bringing temperatures well into the 90s in that region, will weaken as it approaches the region, but as Invest 94L weakens and moves out of the region, the heat surge will reach the region after weakening. 850 mb temperatures are expected to reach 20 degrees celsius on Saturday and Sunday, which in a typical sunny day can produce temperatures as high as the mid-upper 90s. Saturday will bring partly to mostly cloudy skies with the risk of scattered thunderstorms, with temperatures staying in the mid to upper 80s from NYC and further west.

On Sunday, however, as a stronger cold front approaches the region, warmer temperatures are expected, reaching the upper 80s to potentially the lower 90s in the immediate NYC area. Dew points on Sunday are expected to be in the lower 70s, which will result in humid conditions and the heat index reaching the lower 90s in most of the immediate NYC area. Instability is expected ahead of this cold front as well, and strong to potentially severe thunderstorms will form in Pennsylvania and New York on Sunday afternoon as they move east, and will affect the area on Sunday night into Monday as the cold front moves through. Stay tuned for more information on Sunday and Monday’s potential severe weather risk.

Next Week: Significant Uncertainty In The Forecast

Before it appeared that Tropical Depression 13 would form, the expectation for next week was for the cold front to move through followed by a stronger trough, which would bring much cooler temperatures, peaking in the lower 70s in NYC. This scenario no longer appears to be likely, however, as TD-13 and Tropical Storm Katia will be involved in the forecast for next week, bringing significant uncertainty. Some models keep TD-13 stuck in the Gulf of Mexico, while others, especially the GFS, take TD-13’s remnants up the East Coast, bringing a potential round of moderate rain into the region, including the area, during mid-late next week. With the model guidance trending west with Katia, taking it closer to the United States, there is also uncertainty with how Katia will affect the pattern next week, whether it stays out to sea or attempts to move close to the East Coast. The overall idea is there that next week should be slightly cooler than this week, with high temperatures in the 70s more frequent in the tri-state area, but at this time, there is too much uncertainty to make a moderate confidence forecast regarding TD-13, Katia, and how they affect the weather in the Northeast. Stay tuned for more information on next week with Friday night’s update.

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