Jan 14, 2011: Coldest Part Of Winter Starting

***This post is from 2011. Please visit the MAIN PAGE to see the latest forecasts for January 2012.

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Note: Today's discussion is a detailed one, going into the possible scenarios and the factors behind my current forecasts. The 5-Day Forecast will be updated on Saturday morning, with a more simple view of the latest forecast.

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As briefly mentioned last night, this morning proved to be the coldest so far this winter, with low temperatures generally in the single digits away from New York City, with some places even seeing low temperatures colder than at any point during the winter of 2009-2010. Low temperatures in fact were even colder than expected in some places, and even fell slightly below zero degrees in Montomery, Orange County!

Tonight will bring similar temperatures to those of this morning, with the potential for parts of Sussex and Orange county to reach or even slightly drop below zero degrees once again, but other than Tuesday which will be mentioned in more details below, the coldest pattern of the winter is only starting, and with the pattern setting up for the next 1-2 weeks, we may not have seen the coldest temperatures of this winter yet.


Tonight's Outlook: Tonight will be another cold night for the area, with low temperatures at least slightly warmer than those of this morning. With increasing clouds tonight and an exiting cold air mass, low temperatures may peak a little earlier than they would usually do so.

Low temperatures in the lower to mid 0s are expected inland, mid 0s to lower 10s for the north/west suburbs of NYC and southern Connecticut, upper 0s to lower 10s for Long Island with mid 0s in the colder areas and mid 10s in the warmer areas, and mid to upper 10s for NYC. Some readings in the lower single digits are also possible in southern-central Connecticut. A light west wind is expected.

Tomorrow: With a weak low pressure staying to the north of the area tomorrow, warmer temperatures are expected, even though they will still be below the average high temperatures. High temperatures will be in the upper 20s to lower 30s inland, lower to mid 30s in the immediate NYC area, and in the mid 30s for the eastern parts of the area. Note that the area of the mid 30s could be bigger than indicated on the map. A southwest wind is expected.

This low pressure to the north of the area will bring a widespread light to moderate snow for the Northeast tomorrow. Even though it will be too far to the north of the area, it will still manage to bring at least some snow showers to parts of the area, which may bring at least a dusting of snow north of NYC and in southern Connecticut.


Sunday - Monday: Warmer Sunday, Brief Yet Intense Cold For Monday

Sunday will continue the warming trend, with temperatures potentially reaching the upper 30s in the immediate NYC area, which would be the closest the area has been to reaching the average high temperature since early this month. The GFS model's cold bias is apparently coming into play, only showing high temperatures in the lower to upper 20s for Monday which is too cold, therefore I am leaning closer to the NAM model with the forecast for Sunday, with high temperatures in the lower to potentially mid 30s inland, and in the mid 30s for the rest of the area with a few upper 30s possible in the immediate NYC area.

For Sunday night, however, it appears that we may see another cold night, with the potential for low temperatures similar to those of this morning once again according to the GFS model. It handled the low temperatures for this morning better than the other models, and given the scenario for this time frame, I am going with a scenario near, but for now a little warmer than the GFS, with lows slightly warmer than those of this morning. Note though that these lows are not certain yet and are subject to some changes, and it is possible that they could be even colder than what we saw this morning. Depending on what happens with next weekend's cold potential, Sunday night could be one of the coldest nights of this winter, if not the coldest in the case that the extreme cold possibility doesn't happen for the weekend.

Monday will be the coldest day of this brief cold spell. The GFS model once again is considered as an outlier with its cold daytime high bias coming into play, and I am expecting at this time high temperatures in the lower to mid 20s inland and in the mid 20s to lower 30s for the rest of the area.


Monday Night - Tuesday Night: Wintry Mix And Rain Affect The Area

As mentioned over the last several days, a storm is expected to affect the area between Monday night and Tuesday night. Yesterday, there was a lot of uncertainty with the models, however the GFS model was the westernmost solution with a storm track through the Great Lakes. When making the 5-Day Forecast, which put a 100% chance of a snow/mix changing over to rain, I discounted the GFS as a western outlier, and it did end up trending east today. There are still differences with the models with the exact storm scenario, though there are at least some signs of agreement that can give an idea of what we could expect for this time frame.

It appears that we will see a low pressure on Monday night to the west of the area, which will push out most of the cold air mass in place, but may lead to a cold air damming scenario inland in places such as Pennsylvania, where the cold may stick around longer and lead to more snow/ice than in surrounding areas. A low pressure near the coast then is expected to become the main storm as it moves northeast, though the exact timing and location where this happen are still uncertain.

The set up suggests the possibility of snow, potentially mixing with sleet, freezing rain or rain, to start the storm north and west of New York City, with the best chance of this lasting for a more prolonged period of time in the tri-state area being in NW NJ and Orange County. For the immediate NYC area, it appears at this time that any snow or ice accumulation should be light and will change over to rain, though there is uncertainty with the start of the storm, and it is possible that the immediate NYC area could either see plain rain or a longer period of snow/ice to start. Regardless of the scenario, this is not expected to be a significant snowstorm for New York City, instead the potential is there for heavy rainfall of near or over 1 inch if the wetter case scenario verifies, or a more prolonged sleet/ice event north/west of NYC in the colder case scenario. If the heavy rain scenario verifies, it will cause melting of the snowmelt and the potential for flooding in some places. For interior areas, more snow/sleet is expected to start the storm before changing over to a mix/rain, though this could change, especially if the colder case scenario verifies, in which case the western parts of the area may see a mostly snow/ice event, with barely any rain.

Note that there is still uncertainty with the scenario, and it is possible that it could change around some more over the next 1-2 days. Stay tuned for more information on this storm and what effects it may have on the area.


Behind The Storm: Cold Returns, Arctic Air Mass Possible For Weekend

Once the storm moves out, another cold air mass will move into the area. Even though Wednesday's highs will still be mild, potentially in the lower to upper 30s across the area, Thursday will be colder, with high temperatures likely returning into the upper 20s to mid 30s across the area. Cold temperatures are possible again on Wednesday night, however the coldest has yet to come.

Some models, especially the GFS, are suggesting the possibility for another storm to affect the area on Thursday and Friday. At this time, the GFS model is showing this as a clipper type of system that redevelops offshore and intensifies too far east for the area to receive significant snowfall, however with this being in the longer range, the exact scenario is expected to change with future runs. Behind this storm, however, comes the potential for what may be one of, if not the coldest air mass of the winter.

Since early January, when I mentioned the possibility of an arctic air mass around the third week of January in my updated winter outlook, I kept an eye on this potential, which is now starting to become reality. There is model consistency with an extremely cold air mass entering NW Canada around Tuesday. From there, it drops southeast, and while there is uncertainty with what exactly it does, it appears that a strong arctic air mass may affect the area between Friday and Sunday. With this still in the longer range, there is uncertainty on exactly how cold it gets, but if the colder scenario verifies as some models have been suggesting, most of the area may struggle to reach the 20s for high temperatures, and inland areas may fail to reach the 20 degree mark. This is still speculation at this point, and it is possible that the extreme cold never reaches the area and temperatures only get as low as where they have been recently, in the lower to upper 20s. Stay tuned for more information on this potential.