Oct 14, 2011: Colder Temperatures Return Tomorrow

After a round of heavy rain last night affecting parts of the area, the morning hours brought drier conditions, with temperatures rising into the upper 60s to mid 70s across the area. During the afternoon, as a stronger cold front approached from the west, heavy thunderstorms affected most of the area, especially from NYC and further north/west. With the front clearing the area, the storms have ended, and even though isolated showers may be possible tonight into tomorrow, no widespread rain is expected.

This cold front will bring an end to the consistent warmth the area has seen since early October. A stronger cold air mass will move in behind the front into the region, bringing temperatures back down to seasonable levels for this weekend into early next week. As another low pressure system develops to the west of the region, temperatures will slightly warm up ahead of the storm, which may bring moderate to heavy rain for next Wednesday, potentially followed by the coldest temperatures so far this fall.

Weekend Outlook: Mainly Dry, Windy Start

As the low pressure currently near the Great Lakes will continue to intensify, a tight pressure gradient will result in windy conditions across the area tomorrow. A gusty SW wind is expected, with winds of about 15-25 mph across the area, gusting up to 30-40 mph in parts of the area, especially closer to the coast. Partly cloudy skies are expected tomorrow with colder high temperatures, reaching the upper 50s to lower 60s inland and the lower to mid 60s across the rest of the area.

With the low pressure moving further north on Sunday, away from the region, the winds will calm down with partly sunny skies expected again. High temperatures will be similar to those of tomorrow, reaching the lower 60s inland and the lower to mid 60s across the rest of the area. Cloud cover is expected to increase later on in the day, but no showers are expected.

Monday – Wednesday: Clouds Increase, Rain Returns

Mostly cloudy skies are expected to return for Monday as a weak cold front moves through the region, keeping high temperatures in the lower to mid 60s across the area. Temperatures will not cool down behind this front, however, as this will be a weak front, and the cold air will be trapped over southern Canada due to the position of the Polar Vortex over the Hudson Bay in Canada. Due to the weak front, scattered showers are expected on Monday. The first half of Tuesday will bring conditions similar to those of Monday, with partly to mostly cloudy skies and isolated showers. As a low pressure organizes itself further west, towards the central US, however, a warm front will gradually move towards the area, bringing warmer temperatures, reaching the upper 60s in the immediate NYC area.

The latest models have backed away from the stronger storm idea, and trended towards a solution closer to yesterday’s GFS evening run, showing a mostly weak low pressure quickly moving through the region, only intensifying into a strong storm once in Canada. While I expect the models to trend stronger with the intensity of this storm, the probability of a strong negatively tilted low pressure cutting off near the Northeast similar to what yesterday’s models showed is beginning to decrease. The latest expectation is for rain to begin affecting the area on Tuesday night, with moderate to locally heavy rain on Wednesday, and some rumbles of thunder may be possible as well. Stay tuned for more information on Wednesday’s storm.

Thursday – Next Weekend: Cold Returns

Behind the mid-week storm, a significantly colder air mass is expected to move into the region. With the Polar Vortex in place in southern Canada, this low pressure will have cold air to pull into the United States, and although the source of cold air is not strong, it will be capable of bringing widespread cold temperatures into the US. There is some uncertainty with the exact timing and intensity of the cold air, and the GFS model may be overestimating the intensity of the cold air, showing high temperatures in the 40s across the area which is most likely too cold, but if no major changes take place in the expected set up, the coldest temperatures are expected for Thursday through Saturday, and high temperatures are expected to end up in the 50s across the area, and low temperatures will likely reach the 30s and 40s. If there are clear skies as well, frost may be possible in parts of the area. Stay tuned for more information on the potential cold spell late next week.

It does not appear that this cold spell will be sustained, as the last several cold spells have failed to become sustained as well. With the positive PNA and negative NAO trending back towards neutral, and the lack of a strong low pressure to keep the cold air stuck across southern Canada and the Northeast, the cold is expected to weaken, and warmer temperatures are likely to return by the second half of next weekend. Although no major warm spell is expected, temperatures will likely continue to fluctuate between above and near/below average for the longer range. More information on the longer range will be posted as details become clearer.

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