Jan 13, 2012: Snow Finally Fell Today

A strong cold front moved through the region this morning after a round of showers last night, and along with the colder air mass, parts of the area observed moderate snow showers this morning, which was followed by another area of light snow showers that affected a large part of the area in the early to mid afternoon hours. The afternoon snow shower development was unexpected, although the potential was mentioned over the last few days for snow showers in the morning hours. Central Park, however, did not officially record a trace of snow, so Central Park still has yet to officially record snow this month.

Temperatures with the front were much colder, with morning temperatures starting out in the mid to upper 40s across most of the area before dropping into the upper 20s to lower 30s from NYC and further west by 12 PM. Further east, the temperature drop took place later in the afternoon. In addition to the temperatures, strong wind gusts were observed today, with widespread wind gusts above 40 mph. Winds also gusted near or above 50 mph in locations near NYC, Long Island and southern Connecticut, with a peak gust of 52 mph in Newark, 56 mph in New Haven, and a 58 mph gust near Plum Island in Suffolk County.

The winds will weaken for tonight with temperatures staying cold, with Saturday night into Sunday bringing the coldest temperatures, with overnight lows in the upper 0s to upper 10s and Sunday’s highs in the 20s across the area. The cold will remain transient once again, with temperatures returning back to near 40 degrees by Monday with more clouds and rain for Tuesday into Tuesday night. Temperatures will become colder by the second half of next week, although there are increasing signals that the time period starting from next weekend may bring warmer, potentially much warmer temperatures across parts of the region, including the NYC area.

Weekend Outlook: Scattered Flurries Tomorrow?

With a cold and dry air mass in place, partly cloudy skies are expected for tomorrow along with colder high temperatures, reaching the lower to mid 30s inland and the mid 30s across the rest of the area, possibly reaching the upper 30s near NYC. A weak cold front will move towards the area tomorrow afternoon, and while any precipitation will remain isolated, the potential is there for scattered flurries, especially north and west of NYC, after 12-2 PM tomorrow afternoon.

Saturday night will bring the coldest temperatures of the weekend, with temperatures dropping into the upper 0s inland, lower to mid 10s across most of the north/west suburbs of NYC, southern CT and Long Island, with upper 10s in NYC. High temperatures on Sunday will reach the mid to upper 20s across the area along with mainly sunny skies.

Monday – Wednesday: Warmer, Rainy

The cold air mass in place will be quickly pushed out by a developing low pressure approaching the Great Lakes region, with Monday bringing mostly sunny skies along with warmer temperatures, reaching the upper 30s to lower 40s across most of the area. With the warmer air mass still moving in along with increasing clouds and southwest winds, temperatures will only slightly drop on Monday night, rising towards Tuesday morning along with developing showers. More widespread showers are expected to affect the area on Tuesday into Tuesday night as the low pressure tracks through the northern parts of the region, with the cold front moving through sometime on Tuesday night. Light to moderate rain amounts, generally up to 1/2 inch, are likely across the area, along with temperatures on Tuesday peaking around the mid 40s across most of the area. The rain is likely to move out by Wednesday with slightly cooler temperatures. Stay tuned for more information on Tuesday’s storm outlook.

Thursday – Friday: Slightly Colder, A Bit Of Snow?

As we have seen many times with this pattern, a transient cold air mass typically moves in behind rain and mild temperatures, which will be the case once again for late next week. A colder air mass will move into the region by Wednesday night, and while exact temperatures are uncertain, high temperatures between Wednesday and Friday are expected to end up in the 30s, with low temperatures in the 20s. Slightly warmer temperatures are expected for Thursday as a weak low pressure is likely to track to the north of the area, bringing the potential for snow showers for the Northeast, although if it ends up far south enough, isolated snow showers may be possible in parts of the area. Friday will then bring slightly cooler temperatures again.

Longer Range Update: Warmth Possible Beyond 1/20

As I have stated with my previous updates over the last few days, it is increasingly likely that for the second half of the month, especially after 1/20, not only is the pattern not expected to turn cold and snowy, but there is the potential that significant warmth may take place for parts of the US, including the NYC area. After reviewing the latest data, I have more confidence in this scenario, which may bring the potential for above to well above average temperatures at least once, if not more, in the January 20-28 time frame.

Although this time frame is in the longer range, the developments of this potential period of warmth begin in the medium range. Looking at the 18z GFS 500 millibar chart, posted to the left, there are signs showing that there are changes in the pattern, but they are not in favor of cold and snow in the East. In the short range, ridging develops near western Alaska, but this ridging is only transient, quickly moving out as lower heights spread towards Alaska once again, as frequent with this pattern. The map to the left shows that there is ridging near northern Alaska, which is keeping the lower heights further south, resulting in a mostly zonal flow from the Pacific to the Atlantic. Meanwhile, a very large polar vortex will begin to drop into central/northern Canada, with very strong cold air spreading across almost all of Canada and the northernmost parts of the US bordering Canada. Along with the zonal flow in the Pacific and no Greenland blocking, however, there is nothing to allow the cold air to spill south into the United States, with the zonal flow bringing in a mild Pacific air mass into the United States.

**NOTE: The map below represents the POTENTIAL temperature departures IF the pattern described above does set up. The outlook is not final, and it is possible that the significant warmth potential may not set up and temperatures would end up closer to average.**

Beyond this time frame, there is a general model consensus for a stronger ridge to build especially towards the eastern US, while the cold in Canada begins to weaken. With this set up, the potential is there for above average temperatures to cover the majority of the United States, with above to potentially well above average temperatures possible towards the East Coast. Temperatures will not be warm the entire time; there will be some cold spells from time to time, although they will remain transient. Despite this, the potential is there that at least once in this time frame, if not more, temperatures end up much warmer than average in parts of the region, potentially including the area. There is widespread support for this scenario with the medium range models, the ensemble guidance, and especially the NAEFS, which has correctly predicted the consistent above average temperatures since early December even when the GFS model was showing a cold pattern developing for January, with the latest NAEFS medium range outlook showing almost the entire United States with a higher probability for above average temperatures.

This is not likely to be the beginning of a very warm pattern lasting through the rest of the winter, however. This pattern is likely to moderate towards the end of the month, with the best chance of the season’s first accumulating snow event for the area towards the very end of the month or in February, especially if the light snow potential next Thursday night/Friday does not verify. Although the pattern beyond the end of the month is too far away to know with high confidence, there is a better chance that at least some cold and snow may return into the region for February. Stay tuned for more information on the longer range outlook.

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