The first widespread snow event for the DC-to-Philly-to-NYC corridor will take place from later tonight into Sunday morning and this snow event will be followed by bone-chilling cold and biting winds for the rest of Sunday, Sunday night, and Monday. Low pressure will quickly move today across the Plains, Midwest and Ohio Valley and will get a boost later tonight as it reaches the Mid-Atlantic region thanks to strong support in the upper atmosphere. A powerful jet streak will intensify overhead of the I-95 corridor later tonight enhancing upward motion in the area and the result will be an accumulating snowfall focused on the overnight hours and the early morning hours on Sunday. The precipitation could break out as a mixed bag this evening in some areas, but will change to all snow later tonight.
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The next in a series of Arctic air masses will begin to plunge into the north-central states later today and this one will be brutal...potentially the worst of the bunch since the cold pattern developed around Thanksgiving Day. Temperatures this weekend can drop to 20 degrees below zero in parts of the region from Montana to Wisconsin and wind chills can reach dangerously low levels. Meanwhile, yet another “clipper” system will begin to organize later today out across the north-central states and then push east-southeast on Saturday crossing over central Plains, Midwest and Ohio Valley. This system will reach the Mid-Atlantic region on Saturday night and will be supported aloft by a vigorous jet streak that will enhance upward motion in the area. The result will be accumulating snow from Saturday night into Sunday morning in the Mid-Atlantic region and this includes the DC-to-Philly-to-NYC corridor. Bitter cold and strong winds will follow for the rest of Sunday, Sunday night, and Monday.
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In the wake of yesterday’s “clipper” system, another Arctic air mass is pouring into the northeastern states on stiff NW winds and temperatures today will struggle to climb from early day levels. In addition, snow showers are likely in parts of the area and heavier snow squalls can develop causing travel headaches across some interior, higher elevation locations. Another “clipper” system will reach the Mid-Atlantic region on Friday, and it’ll gradually weaken during the day as it loses some of its upper-level support and this will limit its impact on the DC-to-Philly-to-NYC corridor.
By later tomorrow, the next Arctic air mass will plunge into the north-central US from Canada and this one will be brutal...potentially the worst of the bunch since the cold pattern developed around Thanksgiving Day. Temperatures this weekend can drop to 20 degrees below zero in parts of the region from Montana to Wisconsin and wind chills can reach dangerously low levels. Meanwhile, yet another “clipper” system will push east-southeast crossing over central Plains, Midwest and Ohio Valley on Saturday and then into the Mid-Atlantic region by Saturday night. This system will feature some strong support in the upper atmosphere with a vigorous jet streak and has the potential of producing accumulating snow in the Mid-Atlantic region from late Saturday into early Sunday. Arctic air that invades the north-central states on Friday and Saturday will then spread to the northeastern states on Sunday following the passage of this next “clipper” system.
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The next several days will feature multiple “clipper” low pressure systems across the northern US which are typically rather quick movers from northwest-to-southeast. One such system will track well to the north and west of the DC-to-Philly-to-NYC corridor later today bringing windy and slightly milder conditions to the I-95 corridor along with the threat of a few rain showers. A second “clipper” system will push towards the Mid-Atlantic region on Friday from the Ohio Valley. While this system may begin to weaken upon its approach, it can still produce some snow on Friday in parts of the Mid-Atlantic region including the DC metro and parts of Virginia (a hot spot so far this winter season for snowfall).
Over the weekend, yet another “clipper” system will push east-southeast towards the Mid-Atlantic region from the Ohio Valley, and this one will feature some strong support in the upper atmosphere with a vigorous jet streak. As a result, this is the most impressive to me of all of these “clipper” systems with the highest potential of producing accumulating snow in the Mid-Atlantic region (late Saturday into early Sunday). One final note, the Arctic blast that reaches the north-central US by early this weekend and then the Mid-Atlantic/Northeast US by early next week will feature some of the coldest air yet in this relentless cold weather pattern that began around Thanksgiving Day. Temperatures can drop to twenty degrees below zero by Sunday morning across a wide portion of the Upper Midwest from Minnesota-to-Iowa-to-Wisconsin.
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The cold pattern that has brought relentless cold in recent days from Alaska to the Mid-Atlantic region will continue for at least another week or so. The new work week begins with some frigid air in the eastern states and overnight lows in the DC-to-Philly-to-NYC corridor will drop to their lowest levels of the season so far. “Clipper” low pressure systems will swing cold fronts through the northeastern states during the next few days limiting any chance for a sustained warmup. One “clipper” can bring rain, ice and/or snow to the Mid-Atlantic/Northeast US at mid-week and a second system can bring a touch of snow in the late week. Over the weekend, low pressure may ride along the Arctic boundary zone, and this system could bring some accumulating snow to the Mid-Atlantic region to go along with the well below-normal temperatures that should last into the early part of next week.
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An Arctic blast that resulted in numerous record low temperatures this morning across the Upper Midwest/Great Lakes is on its way to the Mid-Atlantic region, and it will set the stage for an accumulating snow event on Friday in the southern half of the area from DC/Virginia to the Delmarva Peninsula to the southern part of New Jersey. Temperatures in the overnight hours will drop into the teens in many of the suburbs along the I-95 corridor following the passage of an Arctic cold frontal system later today. Moisture on Friday will spread to the northeast from the Tennessee Valley and run into this very cold and dry Arctic air mass and snow will break out early in the day across much of Virginia and the DC metro region...in other words, both the AM and PM commutes can be slippery in these areas on Friday.
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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 there will be multiple cold air outbreaks in coming days. Two signals that have foreshadowed a cold period include an unusually early season stratospheric warming event and the movement of a tropical disturbance into a position that favors colder-than-normal weather across much of the nation. In fact, there appears to be a second burst of stratospheric warming in the offing for later this month resulting in a “stretched” polar vortex, and the tropical disturbance will likely persist in much of the same “cold” position” for awhile longer...both of these favor the idea of additional cold air outbreaks as we progress through the month.
The cold pattern has been quite active as well and multiple systems will have to be watched in coming days. On Friday, low pressure will develop over the Deep South and head in an northeasterly direction. This system is likely to produce some accumulating snow in the southern half of the Mid-Atlantic region and looks like a light-to-moderate snow event. Another low pressure system may pull out of the southeastern states by early next week and head in an northeasterly direction at the same time a “clipper” moves southeastward across the Great Lakes…we’ll monitor this activity as it could result in some accumulating snow for the northern Mid-Atlantic and Northeast US. Later next week, it appears a couple of other “clipper” systems will drop southeastward from southwestern Canada into the Great Lakes and ultimately, to the Northeast US. Finally, the significant change in recent days of an index value known as the “Southern Oscillation” is raising a red flag that the chance of an east coast storm will be on the rise somewhere down the road as the sub-tropical jet stream likely becomes activated.
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December has begun on a cold note across the northeastern states and below-normal temperatures are likely on average through at least the first half of the month. Two factors that have been pointing us to an extended cold stretch this month include an unusually early stratospheric warming event over the polar region of the Northern Hemisphere, and the movement of a tropical disturbance along the equator that is moving through locations which favor colder-than-normal weather in the eastern states.
The cold pattern will remain active as well with the next storm system to impact the Mid-Atlantic and Northeast US on Tuesday, and this follows a significant Great Lakes snow event late last week and a major snowstorm in the Midwest this past weekend. The best chance for significant snow on Tuesday will be across the interior sections of the northeastern states where several inches of snow are likely and heavy rain is the main threat along coastal areas from southern New Jersey to the Delmarva Peninsula. The I-95 corridor will be in the “battle zone” region for awhile on Tuesday morning with snow and ice likely at the front end that will transition to plain rain for the main part of the storm. Small snow accumulations are possible before the transition to plain rain with a coating to an inch or so possible in some of the northern and western suburbs...watch for slick spots during the AM hours.
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Several inches of snow will pile up this weekend across a large part of the Midwest and Great Lakes (where they are still reeling from some intense lake-effect snow bands) and another winter storm will hit the Mid-Atlantic region and Northeast US on Tuesday. The best chance for significant snow on Tuesday will be across the interior sections of the northeastern states and heavy rain is the main threat along coastal areas from southern NJ to the Carolinas. The I-95 corridor will likely be in a battle zone period for awhile on Tuesday with some accumulating snow and ice possible at the front end, but a changeover to rain is likely; especially, in the big cities from DC-to-Philly-to-NYC.
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The period between Thanksgiving and Christmas will begin with a major Great Lakes snow event from Thursday to Friday and an Great Lakes/Midwest snowstorm this weekend and it could end with a White Christmas in many parts of the country. Two of the factors that have been highlighted here, likely leading to a cold and active stretch of weather, include an unusual early season stratospheric warming event and the likely movement of a tropical disturbance into a location that favors colder-than-normal conditions across a large part of the nation. Both of these phenomena – stratospheric warming and tropical forcing – will likely lead to a “buckling” of the polar jet stream which can lead to the unleashing of multiple Arctic air masses from northern Canada into the US (with intense cold in the table), and an activation of the southern branch of the jet stream which will likely produce multiple snow/ice threats.
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