Nov 30, 2011: Chilly, Dry End To Week

With yesterday’s storm out of the region, the ridge that produced record breaking warmth across the region for the last several days has finally moved out, with colder temperatures returning into the area. With partly cloudy skies, high temperatures reached the upper 40s inland, lower 50s in the immediate NYC area, and the lower to mid 50s in Long Island and southern Connecticut. Although these temperatures are much colder than the 70 degree highs observed just two days ago, today still ended up slightly warmer than the average high temperatures, which are currently near 50 degrees.

With weak troughs moving into the region, temperatures will remain slightly above average through Friday, similar to today’s temperatures. A strong high pressure will provide sunny skies for the area on Saturday with slightly below average temperatures, peaking below 50 degrees across most of the area, but yet another ridge will build, bringing yet another potential for 60+ degrees early next week. Although this will certainly not be the last surge of mild temperatures in December, it is likely to be the last 60+ degree warm spell for a while, as a temporarily colder pattern affects the region afterwards.

Tomorrow’s Outlook:

Tomorrow will bring temperatures similar to those of today across the area. With mostly sunny skies, high temperatures will reach the upper 40s inland, and the lower 50s across the rest of the area. A NW wind is expected tomorrow.

Friday – Monday: Chilly Start, Warm End; 60+ Degrees Return?

As a very weak low pressure moves through the northern Northeast, bringing light snow showers to central and northern New England, temperatures will slightly rise in the area, reaching the upper 40s to lower 50s inland, and the lower to mid 50s across the rest of the area. Increasing clouds are expected towards Friday afternoon, with partly cloudy skies by the evening hours, although as a trough moves into the area, skies will clear overnight as colder temperatures return, dropping into the mid 20s to lower 30s across most of the area. Saturday will be the coldest day of this time frame, with slightly below average highs possible, reaching the mid to upper 40s inland and the upper 40s to lower 50s across the rest of the area, with sunny skies expected as a strong high pressure moves over the region.

Following the pattern over the last month, the set up for Sunday and Monday becomes easily predictable. The high pressure will move offshore, with SW winds bringing warmer temperatures into the region, and with a low pressure developing in the central US, yet another ridge will build into the eastern US. Although this ridge won’t bring temperatures as warm as those of last weekend and the early week, well above average temperatures are expected again. Mostly to partly sunny skies are expected on Sunday with highs reaching the lower to mid 50s across the area, possibly in the upper 50s in parts of the immediate NYC area, and with partly cloudy skies on Monday, high temperatures are likely to reach the upper 50s across the area, with lower 60s likely as well in the immediate NYC area.

Tuesday – Friday: Stormy, Then Colder

The map above shows that a wave of low pressure is expected to develop along the cold front on Monday over the southeastern US, bringing heavy rain. This wave of low pressure will keep dry conditions on Monday, but will slowly move northeast, bringing cloudy skies across the area on Tuesday. There is some uncertainty with the timing, as some models quickly bring the front through on Monday night, others such as the GFS bring the front through on Tuesday night, and the ECM stalls the front over the area with moderate to heavy rain lasting through Thursday, but at this time, I am siding with a slower solution, not as slow as the ECM but not as fast as some of the other models, where the front moves through the area around Wednesday, bringing rain between Tuesday and Wednesday, potentially into Wednesday night in the slower case scenario or early Wednesday morning in the faster case scenario. The timing could still change over the next few days, and if the storm ends up far west enough on Tuesday that the rain does not move over the area, even warmer temperatures may be possible on Tuesday with rain on Wednesday into early Thursday. Stay tuned for more information on the early-mid week storm.

Behind this storm, the models have significantly backed away from the intensity of the cold coming in behind the storm. A few days ago, the GFS, ECM and CMC consistently showed a strong trough dropping into the region. With their latest runs, the ridge over the southeastern US fails to fall apart, and instead a brief cold spell moves through the area before temperatures warm up again towards the weekend. Looking through the longer range, the lack of blocking near Greenland continues as the NAO and AO remain positive, with the PNA turning towards negative, all of these phases unfavorable for cold in the eastern US. The ridge in the SE, known as the Southeast ridge, weakens but fails to fall apart, with most of the cold spells through at least 12/15 expected to focus over the central US, weakening as they move towards the East Coast. As a result, it is now becoming likely that temperatures through 12/15 will likely end up near average, potentially slightly above average. Occasional cold spells are expected in this time frame, potentially bringing snow to parts of the Northeast, but the pattern will remain unfavorable for any sustained cold and snow, with no snow potentials in sight for the NYC area in the near future.

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