Saturday, December 31, 2011
Dec 31, 2011: Cold First Week Of New Year
A weak clipper moved through the region yesterday into today, bringing widespread showers across the region along with yet another round of unseasonably warm temperatures, peaking on Friday in the mid 40s to lower 50s across the area, followed by warmer temperatures today in the lower 50s inland, lower to mid 50s in the immediate NYC area, and the lower 50s in Long Island and southern Connecticut. The average high temperature for this time of the year are near the upper 30s to lower 40s.
After a dry and unseasonably mild New Year's Eve, with partly to mostly cloudy skies and temperatures in the lower 40s at midnight, one more day of mild temperatures is expected for tomorrow, with temperatures again reaching the upper 40s to lower 50s, followed by the first significant cold spell of the winter for Tuesday and Wednesday, with widespread highs in the 20s and lows in the single digits and teens. This significant cold spell is showing that there are minor changes in the pattern, but the pattern still has not changed, as a ridge in the eastern US will quickly build in behind this cold spell with high temperatures once again returning into the upper 40s and 50s towards next weekend.
The first day of 2012 will bring unseasonably mild temperatures once again, with partly sunny skies and temperatures peaking in the upper 40s to lower 50s inland and the lower to mid 50s across the rest of the area. Cloud cover is expected to increase towards the evening hours as a cold front approaches, however only isolated showers at most are expected out of this front on Sunday night.
Monday - Wednesday: Much Colder, Windy
With the cold front east of the area, Monday will bring partly to mostly cloudy skies with the risk of an isolated shower across the area. Colder temperatures are expected, with temperatures reaching the upper 30s to lower 40s inland and lower to mid 40s across the rest of the area, along with breezy winds. Behind the cold front, however, unlike the previous cold spells over the last two months, there is nothing to prevent the arctic air in central Canada from dropping south, and as a result, very cold arctic air will spill southwards from Canada into the central and eastern United States.
The first part of the cold will be felt on Monday night into Tuesday, with temperatures on Monday night dropping into the mid 10s to lower 20s west of NYC and the lower to upper 20s from NYC and further east. With temperatures aloft steadily cooling down, temperatures on Tuesday afternoon will not rise by much, staying steady in the lower to mid 20s inland and the mid to upper 20s across the rest of the area, dropping by the late afternoon hours. Gusty winds are expected as well, with gusts up to 40 mph; combined with the cold temperatures, wind chills will stay in the upper single digits to lower 10s throughout the day inland, and in the 10s for the rest of the area.
The coldest temperatures are expected for Tuesday night. Mostly clear skies are expected, which combined with 850mb temperatures near -20 degrees Celsius, will allow temperatures to significantly drop overnight, with low temperatures expected to end up in the mid to upper single digits inland, upper 0s to mid 10s in the north/west suburbs of NYC, upper single digits to lower 10s in southern CT, upper 0s to mid 10s in Long Island, and mid to upper 10s in NYC. Combined with gusty winds, especially in the evening, wind chills will drop into the single digits across the entire area, with sub-zero wind chills possible inland. A Wind Chill Alert will likely be issued for the interior parts of the area with tomorrow's update. Cold temperatures will continue through Wednesday along with mostly sunny skies, with highs reaching the mid to upper 20s across the area.
Longer Range: Warming Up Again
The fact that a strong cold spell is affecting the region is a sign that there are minor improvements in the pattern. The cold, however, is not a sign that the pattern has changed, as there is still a polar vortex near Alaska and the Davis Strait west of Greenland, two indications not supporting any sustained cold and snow pattern in the region, along with zero blocking developing. Unlike last year, when by this time of the year a strong -NAO/-AO blocking pattern has been established near Greenland, there has not been blocking so far this winter, and with the pattern in place, no blocking will set up at least through the next 10 days, if not beyond that range. With the progressive pattern due to the lack of blocking, there will be nothing to keep the cold stuck in place, and a warmer air mass will once again return by the late week, with temperatures once again rising into the upper 40s to lower 50s across the area by Friday. The longer range beyond Saturday is more uncertain due to the time range, although a low pressure will move through the region over the weekend, bringing more cloud cover along with the potential for some precipitation, followed by another transient cold air mass for the start of next week.
Posted by NYC Weather at 8:19 PM