The combination of a weakening “clipper” low pressure system and an intensifying ocean low that is to develop an inverted trough will raise the chance of some accumulating snow from later tomorrow into early Saturday across parts of the Mid-Atlantic region. There can be a coating to as much as 2 or 3 inches of snow by early Saturday across portion of eastern PA, much of New Jersey, and the New York City metro region and a coating of snow is possible as far south as the DC metro region. As the intensifying ocean low exits off to the northeast on Saturday, the door will be open for the coldest air mass of the season to ride into the Mid-Atlantic region on stiffening NW winds. A look ahead to early January suggests there will be the return of “high-latitude blocking” across Canada which tends to favor colder weather in the central and eastern US and teleconnection indices support the notion of an overall colder weather pattern.
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The combination of a weakening “clipper” low pressure system and an intensifying ocean low that develops an inverted trough will raise the chance of some accumulating snow from later Friday into early Saturday across the northern Mid-Atlantic region to include eastern PA, New Jersey and New York City. Farther to the south, snow showers are possible in the DC metro region by Friday night, but accumulating snow there is less likely than to the north of the PA/MD border. As the intensifying ocean low pulls away to the northeast on Saturday, the coldest air mass of the season so far will ride into the Mid-Atlantic region on stiff northwest winds and the lowest temperatures in this cold snap are likely to occur early Monday morning.
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There have been many football games played in cold weather over the years at Penn State’s Beaver Stadium, but this one coming up on Saturday will be the first of its kind as an official playoff game under the new format by the NCAA. In fact, the coldest air of the season will pour into the Mid-Atlantic region and Northeast US from this weekend into early next week on the backside of strengthening low pressure over the western Atlantic Ocean. The lowest temperatures in this upcoming cold blast are likely to occur early Monday morning with upper single digits on the table for places like State College, PA, and the lower teens possible in many suburban locations along the DC-to-Philly-to-NYC corridor...pretty impressive readings indeed considering there is no snow cover in the I-95 corridor. Temperatures will turn much milder early next week across the central US and a moderation in temperatures will reach the eastern seaboard by Christmas Day which falls on Wednesday of next week.
As far as snow is concerned, there is the chance for snow shower activity on Friday and Friday night in the Mid-Atlantic region and perhaps even a period of steadier snow. The combination of a “clipper” low pressure system dropping to the south and east from the Great Lakes and developing low pressure over the western Atlantic will bring us the threat of snow. The speed at which these two systems “link up” will dictate how much snow can fall on Friday and Friday…small accumulations are on the table and the situation bears watching during the next few days.
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The month of December has started off with a few Arctic air outbreaks into the central and eastern US and while the overall pattern may turn somewhat milder for part of next week, there are multiple signals pointing to additional cold air outbreaks from later next week into the month of January. In addition, the unfolding weather pattern appears to be quite active with numerous storm systems to deal going through the second half of the month of December.
One of the signals for additional cold air outbreaks revolves around an oceanic-atmospheric phenomenon known as the Madden-Julian Oscillation or MJO. A second centers around a phenomenon that features warming over the polar region in the upper part of the atmosphere known as the stratosphere. Finally, a teleconnection index known as the Pacific-North American (PNA) is likely to feature a positive phase for much of the rest of the month and this generally favors high pressure ridging across the western US and Canada which, in turn, is usually favorable for cold air outbreaks to make their way from northern Canada into the central and eastern US.
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There was some rainfall in the DC-to-Philly-to-NYC corridor on Monday which was certainly a welcome happening; however, overall totals were on the low side due to the quick movement of the low pressure system. The rain event coming from late Tuesday night through Wednesday will be quite a different story, however, and likely the biggest single rainstorm in this area since early June. Rainfall amounts can exceed 2 inches all along the I-95 corridor and a few thunderstorms can mix into the picture. The combination of a strong surface cold front, plenty of available moisture, and a deep upper-level trough that becomes “negatively-tilted” will lead to this heavy rain event
In addition to the rain, the winds will become an important factor; especially, along coastal sections of the eastern seaboard from the Carolinas to New England where a low-level jet is going to become very intense. In fact, there is the potential for winds to gusts to 60 mph late Wednesday across portions of eastern New England where the low-level jet will reach its greatest strength.
In terms of temperatures, it’ll be unseasonably mild through much of the day on Wednesday - ahead of the strong cold front - temperatures will drop sharply late in the day or early tonight on the heels of its passage. This cold air intrusion can lead to a brief period of snow in some of the N/W suburbs along the I-95 corridor where small accumulations cannot be ruled out this evening. Finally, this cold blast will result in yet another “Great Lakes snow event” for those areas just downstream of Lakes Erie and Ontario (e.g., Erie, PA, Watertown, NY).
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There has been some rainfall today in the DC-to-Philly-to-NYC corridor which is certainly quite welcome; however, overall amounts will end up being on the low side. Another rain event will follow by mid-week in an active weather pattern and this one is likely to feature significant rainfall that can exceed 2 inches all along the I-95 corridor with a few thunderstorms likely to mix into the picture. In addition to the rain, the winds might become very strong both ahead of the advancing cold front from a southerly direction and also on its backside from a northwesterly direction. In fact, wind gusts to extreme levels of 80+ mph are on the table late Wednesday/Wednesday night near and along the strong cold front along the coastal sections from eastern North Carolina to eastern New England. The combination of a strong surface cold front, plenty of available moisture, and a deep upper-level trough that becomes “negatively-tilted” will lead to this heavy rain event from late Tuesday night through Wednesday evening. A cold blast will follow the passage of the cold front for Thursday and Friday with temperatures on both days well below-normal for this time of year.
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The weather on Oahu, Hawaii in the early morning hours of Sunday, December 7th, 1941 was not at all unusual for the time of year with mild temperatures and mainly clear skies. Unfortunately, the weather conditions on that particular day would play a role in the bombing of the U.S. naval base by Japanese fighter planes at Pearl Harbor near Honolulu, Hawaii. As Japanese fighters crossed the Pacific Ocean, they were given hope that their mission would succeed when the announcement was made of “clouds mostly over the mounts…visibility good”. It is believed that the decision to attack on that particular day had plenty to do with the projected favorable weather conditions.
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Low pressure will move in a general “west-to-east” fashion across southern Canada during the next 48 hours and it will strengthen dramatically by the time it reaches the Canadian Maritime Provinces on Friday morning. This intensifying storm system and its associated strong cold front will have a big impact on the Great Lakes, Mid-Atlantic and Northeast US between later today and Friday to include some accumulating snow, possible snow squalls, powerful and potentially damaging wind gusts of 50 mph or so, and the ushering in of another Arctic air mass which will produce the lowest wind chills of the season so far.
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The month of December has gotten off to a cold start across much of the eastern half of the nation and it should stay colder-than-normal right through the upcoming weekend. A strengthening low pressure system will move across southern Canada during the next couple of days reaching the Canadian Maritime Provinces by late Thursday and this system and associated cold front will have multiple weather impacts on the Great Lakes, Mid-Atlantic and Northeast US.
To begin, this storm system is likely to add to the on-going “lake-effect” snows across the Great Lakes during the next couple of days and it will also produce some accumulating snow in the interior, higher elevation locations of the Mid-Atlantic and Northeast US. Even the I-95 corridor region from DC-to-Philly-to-NYC-to-Boston can experience small accumulations of snow from later tomorrow night into Thursday with the combination of snow showers and perhaps even a heavier snow squall. In addition, winds will become a big factor with a stiffening southwesterly flow of air out ahead of the approaching strong cold front and then potentially damaging gusts to 50 mph or so from a northwesterly direction on Thursday following the passage of the front. One last impact will be the influx of another Arctic air mass that will flood the northeastern states riding into the region on those powerful NW winds and likely resulting in the lowest wind chills of the season so far.
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The month of December has gotten off to a cold start across much of the nation and it’ll stay colder-than-normal in the DC-to-Philly-to-NYC corridor right through the upcoming weekend. The potential for any significant snow during this time period is quite limited; however, a “clipper” type of low pressure system can bring snow and/or rain showers here from later Wednesday night into early Thursday and small accumulations cannot be ruled out. More important weather impacts associated with this “clipper” system will include powerful winds that can gust past 45 mph or so on Thursday and the influx of another Arctic air mass into the Mid-Atlantic region for the end of the week.
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