Nov 9, 2011: Some Rain, Then Colder

With the strong ridge persisting over the East Coast, today brought well above average temperatures to the area once again, with high temperatures ending up in the mid to upper 60s from NYC and further west and the lower to mid 60s in Long Island and southern Connecticut. Today was the last day of the mainly sunny and warm conditions for now, however, as a strong trough will move into the region tomorrow, bringing mainly cloudy skies and scattered showers, followed by much colder and windy conditions for Friday and Saturday.

The cold spell will only be brief, however, as the current pattern does not support sustained cold spells, and another large ridge will build into the eastern US for Sunday and the first half of next week. The trend of a lack of significant rain events in the area started in late October will continue again, however, as no major rain event appears to be on the way, although some rain is likely for the middle of next week as a cold front moves through, bringing another brief cold spell.


Tomorrow's Outlook:

With the cold front moving towards the area tomorrow and Tropical Storm Sean approaching from the SE, stormy conditions will affect the region. Sean itself will not be the main storm, as parts of Sean will become a stronger extra-tropical storm that will move east of New England on Thursday night. This will keep scattered showers in the area between the afternoon and early overnight hours in the area, although less than 1/4 inch of rain is expected from NYC and further west, with the potential for over 1/2 inch in eastern Long Island and SE CT. Due to the increased cloud cover and the cold front moving through, high temperatures will be colder, peaking in the upper 50s to lower 60s inland and the lower to mid 60s across the rest of the area. With the front moving through, variable wind direction is expected tomorrow, although a mostly WNW wind will develop by the evening.


Friday - Sunday: Cold/Windy Start, Sunny/Mild Ending

With the extratropical storm moving into Canada, a strong trough will move into the region, bringing 850 mb temperatures to near -6 degrees celsius. Along with mostly to partly cloudy skies and a a gusty west/WNW wind, gusting up to 30-40 mph in parts of the area, much colder high temperatures are expected for Friday, peaking in the mid to upper 40s inland, upper 40s to mid 50s in the immediate NYC area, and the lower to mid 50s in Long Island and southern Connecticut.

The current pattern we are in does not favor sustained cold spells over the region. With a strong -PNA pattern keeping a trough over the western US, sustained cold is not favored in the eastern US, although a weak east based -NAO is allowing for some brief troughs to drop into the region. With yet another trough dropping into the western US, the trough in place will quickly lift out of the region, with a strong ridge building by Sunday. Temperatures will slightly warm up throughout the weekend with mostly sunny skies, peaking in the mid 50s in the immediate NYC area and the lower to mid 50s elsewhere on Saturday, and the lower 60s in the immediate NYC area and upper 50s to lower 60s elsewhere on Sunday.


Next Week's Outlook: Warmer Start, Colder Ending

As another low pressure stays north of the Great Lakes region during Sunday, a weak cold front will approach the region on Monday but will fail to move through. As a result, mostly cloudy skies are expected with SSW winds and the risk of isolated showers across the area. In the scenario that it does not rain, warmer temperatures are expected, reaching the lower to mid 60s across the area, and parts of NE NJ and further southwest may exceed the 65 degree mark if there is more sunshine than currently expected. More widespread showers than currently modeled may keep the temperatures slightly lower.

By Tuesday, a stronger low pressure is expected to develop near the Ohio Valley/Great Lakes region, moving northeast. This low pressure will keep the mild temperatures in place for Tuesday across the area with partly to mostly cloudy skies still expected, and at this time, there is a stronger model consensus for the cold front to move through during Wednesday. As a result, rain is expected to affect the area on Tuesday night into Wednesday, although no widespread moderate-heavy rain is expected at this time. There is still some slight uncertainty with the exact timing, and it is possible that the front may move through a little earlier or later than currently expected.

(This section was revised on the morning of 11/10). There is more uncertainty for the second half of next week due to the time range, although it is likely that another trough tries to move into the region behind this storm. There is uncertainty with the timing, as some models keep the front stuck nearby with another storm for the late week. The GFS, which is the fastest and driest model, only has weak ridging in the western Atlantic, which may be too weak given that the majority of the other models show a stronger ridge, which would make it more difficult for the trough to move in immediately. One possible scenario is where the front then moves through with mostly dry conditions in the second half of the week followed by a high pressure building in by Friday/Saturday, although as some of these models are suggesting, another low pressure may be possible in the second half of the week. Tonight's update will discuss this in more details, along with a discussion for the pattern towards end of November into December.