Oct 17, 2011: Wednesday Storm Discussion

Note: The dates for the long range outlooks have been slightly revised; my preliminary winter outlook will be posted on Monday, October 24, and the updated November outlook will be posted on October 31.


Today brought similar conditions to those of yesterday across the region once again, with partly sunny skies and high temperatures near to slightly above average, reaching the mid 60s inland and the mid to upper 60s across the area. Tomorrow will bring similar conditions to those of today, but on Wednesday, a significant storm will affect the region, bringing heavy rain with 1-2 inches of rain expected. Windy conditions will once again return into the region with colder temperatures behind the storm, and while no strong cold is expected in the short range, the potential is there for a colder ending to October.

Tomorrow’s Outlook:

Tomorrow will bring conditions similar to those of today once again. Partly sunny skies are expected across the area with a light south wind expected. High temperatures will reach the mid 60s inland and the mid to upper 60s across the rest of the area, with a few places in NE NJ reaching 70 degrees.

Wednesday – Thursday Storm Discussion

The next storm will affect the region between Tuesday night and Thursday morning. Over the last few days, the models had a hard time handling this storm, first showing the storm over the Northeast, then keeping the storm mostly offshore, and now the latest consensus shows the storm getting as far west as Michigan and western Ohio. There does not appear to be more room for the storm to trend west, however, and as a result, for tonight’s forecast, I followed the model consensus for the track.

A weak surface low pressure is expected along the eastern Mid Atlantic coast on Wednesday associated with a tropical disturbance currently affecting Florida, which will bring tropical moisture up the coast. The upper level low, however, will be over Kentucky, and on Wednesday night, a stronger surface low will form under the ULL, taking the low pressure into Ohio while stalling it near northwestern Ohio/SE Michigan. Once the storm becomes vertically stacked, it will begin to weaken while drifting into Canada on Thursday.

Forecast for NYC Area: For the NYC area, this change in the scenario only has a minor change in the forecast, and as a result, I kept the forecast mostly the same from last night’s update but with a few small changes. Rain is expected to enter the area from the south around 3-5 AM, and will intensify, with moderate to heavy rain during the morning into the early afternoon hours, up until at least 3-4 PM. With the warm front to the south of the area, temperatures will remain in the mid 50s to lower 60s from NYC and further west and in the lower to mid 60s in Long Island/S CT with an east wind. As the warm front moves through, the rain will taper off to scattered showers by the evening as temperature begin to slowly rise, peaking in the lower to mid 60s inland and the mid to upper 60s across the rest of the area during the overnight hours. The storm’s cold front will move through in the middle of the overnight hours after 12 AM, bringing scattered showers and thunderstorms to the area, and the rain is expected to end by 3-5 AM.

By the time that the storm ends, at least 1 to 2 inches of rain are expected to fall across the area. The lightest amounts are expected to be towards NW New Jersey and SE NY, where 3/4 to 1.5 inch of rain is expected, with the heaviest rain amounts in Long Island and southern Connecticut, where 1 to 2 inches of rain are expected, locally up to 2.5 inches. Stay tuned for more information on Wednesday’s storm.

Thursday – Sunday: Cooling Down, Frost Possible

With the low pressure briefly cutting off from the main flow on Thursday, the source of cold air from Canada will be cut off as well, which will prevent the region from seeing the strong cold potential shown several days ago on the models. The cold air mass will weaken while drifting towards the region as the low pressure exits the region, but with 850 mb temperatures near zero degrees celsius, the coldest they’ve been so far this fall, cold temperatures are still expected to affect the region, with frost possible by the weekend.

After temperatures peaking in the 60s on Wednesday night, Thursday will bring colder temperatures behind the front, with high temperatures reaching the upper 50s to lower 60s inland and the lower to mid 60s across the area. A strong SW wind is expected similar to that of Saturday; winds are expected to reach 15-25 mph across the area on Thursday, with gusts up to 30-40 mph once again. Friday will bring colder high temperatures, reaching the mid to upper 50s inland and the upper 50s to lower 60s across the rest of the area.

There is some uncertainty on whether Friday night or Saturday night will be the coldest nights, but regardless, both night will bring cold temperatures. With mostly clear to partly cloudy skies expected, low temperatures will drop into the mid to upper 30s inland, upper 30s to lower 40s in NE NJ and southern CT, lower 40s in Long Island, and mid 40s in NYC. The potential is there for frost in the interior parts of the area for either night.

As mentioned over the last several days, Wednesday’s storm will exit the region without sticking around like last Friday’s storm did, and with no blocking over Canada and a lack of a -NAO to maintain the cold, the trough will weaken, with moderating temperatures returning to the average by the weekend, bringing high temperatures back into the lower to mid 60s across the area.

Monday And Beyond: Colder Ending To October Possible

The current pattern across the region is a transient one, with a lack of blocking in Canada and cold spells failing to become sustained over the region. While it does not appear that strong, sustained blocking will form in the near future, the potential is there for a strong cold spell towards the end of October. Despite a -PNA and +NAO, factors which are typically unfavorable for strong cold spells, the AO, or the Arctic Oscillation, is expected to drop negative after October 25th, about the same time that the model consensus shows a strong arctic air mass moving towards central Canada. This is still in the longer range and is subject to change, and it is possible that the strong cold fails to reach the US, but the potential may be there for a strong surge of cold air towards the last few days of October, along with a storm potential in the East Coast around the 26-28th. More information on the long range will be posted as details becomes clearer.

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