Sept 27, 2011: Cold Start To October

With a cut off low remaining stationary over the Ohio Valley, today brought conditions similar to those of the last three days, with mostly cloudy skies and warm/humid conditions observed once again. High temperatures were slightly cooler than those of yesterday, peaking in the upper 70s to lower 80s from NYC and further west and in the upper 70s across most of Long Island and southern Connecticut.

The cut off low will begin to drift further east on Wednesday, which will push the rain further east once again, bringing rain back into the NYC area for Wednesday and Wednesday night. As the cut off low merges with another low pressure in Canada, a cold front will move through on Thursday bringing more widespread moderate to heavy rain. Behind the front, temperatures will cool down on Friday with clearing skies, but as a colder air mass moves in from Canada, temperatures will significantly cool down for next weekend, bringing an unseasonably cool start to October.

Tomorrow’s Outlook:

Tomorrow will bring colder temperatures into the area. As the upper level low begins to shift further east, the rain bands will move slightly to the east as well, affecting central Virginia into central/western New York. 850 mb temperatures will once again remain near 14-15 degrees celsius, but cloudy skies are expected along with scattered showers, which will lower the temperatures once again. High temperatures will peak in the lower 70s inland, mid 70s in the immediate NYC area, and in the lower to mid 70s across most of Long Island and southern Connecticut with an east wind expected.

Thursday – Friday: Rain Continues
As the upper level low continues to slowly drift east, reaching Ohio by Thursday, the rain bands will begin to shift east as well. With the storm starting to merge with another storm dropping down from Canada, a stronger cold front will move through the area late on Thursday, bringing a widespread moderate to locally heavy rain event across the area. This rain will not be as heavy as last Friday’s rain event, but regardless, rainfall amounts are expected to end up between 1/2 and 1 inch across the area with amounts locally as high as 1.5 inch west of NYC. Due to the cloud cover and rain, temperatures will be cool once again, peaking in the lower to mid 70s across most of the area with a few upper 70s in the immediate NYC area.

With the cold front moving through the area, Friday will bring drier conditions with partly to mostly cloudy skies. Isolated showers cannot be ruled out, but overall, Friday will be much drier than Thursday. As the storm from Canada, merged with the upper level low, continues to organize itself, another cold front will move towards the area on Friday, which will keep mild temperatures in place, with high temperatures peaking in the lower 70s inland and in the mid 70s across the rest of the area. A few upper 70s may be possible near NYC in the warmer case scenario.

Next Weekend: Cold Start To October

The combination of the Canadian storm and the upper level low will help pull in a strong trough from Canada. 850 mb temperatures are expected to be as low as -8 degrees celsius with this air mass when it enters the north central US. With the second front moving through the area on Friday night, temperatures will be cooler on Saturday, peaking in the lower to mid 60s inland and in the mid 60s acrosss the rest of the area. Meanwhile, the cold air mass will dig into the western parts of the region, and will slowly approach the area.

With the front not too far offshore and an upper level low expected over the region, the cold air mass will weaken as it reaches the area, with 850 mb temperatures expected to end up near zero degrees celsius across the area. When combined with partly to mostly cloudy skies and a northwest wind, this will produce unusually chilly temperatures. Saturday night will be the coldest night, with temperatures expected to drop into the 30s inland and into the lower 40s potentially as far as the immediate north/west suburbs of NYC. For Sunday, temperatures are expected to peak in the 50s across the area, likely in the lower to mid 50s inland and the mid to upper 50s in the rest of the area. Stay tuned for more information on the cold spell for this weekend.

Next Week: Warming Up


This cold spell will only be short lived. As the image above shows, warmth will push in from the west once this cold spell will end, bringing a surge of warmth into the region along with a high pressure providing the area with sunshine and dry conditions for next week. Uncertainty comes into the picture when another trough from Canada becomes involved, however, as some models push this trough straight into the region, keeping any warmth short lived, while other models keep the warmth locked over the region, bringing a significant surge of warmth. There is still time for this scenario to change, but at this time, I am expecting the trough to mostly affect the Northeast, with places from NYC and further west/south affected by this surge of warmth more directly. Temperatures should warm up into the 70s again by the middle of next week, with parts of the Mid Atlantic expected to reach the 80s. If the warmer case scenario verifies, temperatures into the lower 80s may get as far north as NYC, but this is highly uncertain and depends on the location of the trough. Stay tuned for more information on next week’s outlook.

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