12:00 PM | ***Slow-moving storm system to impact the Mid-Atlantic region...first snow in many spots along I-95 corridor...significant snow in many higher elevation locations...additional cold shots***
Paul Dorian
This late week cold shot into the northeastern states will not be the last as the unfolding weather pattern has quite the wintry look to it for the northern US with additional cold shots destined to make their way from Canada into the US. Maps courtesy NOAA, tropicaltidbits.com
Overview
If you are a skier in the northeastern part of the country then this upcoming storm system will be quite good news as early season significant accumulating snow is likely in much of the Appalachian Mountain chain including in the region from West Virginia to the Laurel Highlands of southwestern PA and from the Poconos in northeastern PA to the Catskills and Adirondacks of upstate NY. In fact, snow is quite possible during this event all the way into the I-95 corridor and small accumulations are possible on Friday in some of the northern and western suburbs; especially, to the north of the PA/MD border.
A deepening trough of low pressure in the upper atmosphere will slide south and east to a position over the Mid-Atlantic by tomorrow night and this will help to spawn a (secondary) low pressure system near the northern Mid-Atlantic coastline. This system will become a slow-mover thanks to intense blocking high pressure to the north that will be parked over northeastern Canada. In addition to the threat for the first snows of the season, the northeastern states will experience very beneficial rainfall on the storm’s front end as a cold front pushes through from late today into early Thursday…and that won’t be the end of the precipitation.
Looking ahead, there are signs for multiple cold air outbreaks to make their way from northern Canada into the central and eastern US as we push through the remainder of November and into the early part of December.. It is quite a wintry look to this unfolding weather pattern that will include additional snow threats…perhaps one late next week right around Thanksgiving Day.
The deepening trough that pushes into the Mid-Atlantic region by late tomorrow will be forced to rotate around the northeastern states for a few days thanks to intense blocking high pressure stationed to the north over NE Canada. Map courtesy NOAA, tropicaltidbits.com
Details
Today will be the last of the mild and quiet days across the northeastern states for quite awhile as a significant storm system is on the way that will have an impact from early tonight through much of the upcoming weekend. An upper-level trough of low pressure will push from the Northern Plains today to the Mid-Atlantic region by late tomorrow and it will deepen as it drops southeastward. Once in that position, this system will be “forced” to rotate around the northeastern states for a couple of days thanks to intense blocking high pressure to the north that will be centered over the northeastern part of Canada. At the surface, an initial surface low pressure system will push into the Great Lakes, and then a secondary low will form later tomorrow somewhere near the northern Mid-Atlantic coastline and it’ll become the main player on the field as far as the Mid-Atlantic/NE US is concerned.
On the front end of the storm, very beneficial rainfall associated with an advancing cold front will push into the DC-to-Philly-to-NYC corridor early tonight and last until early Thursday and - dare I say - it may actually be heavy at times. This will be the highest rainfall amount in several weeks from a single weather event across many sections of the I-95 corridor with at least half an inch possible in the DC metro area and an inch or so is possible from Philly to NYC by early tomorrow...a thunderstorm or two may be mixed in. Winds will also become a major factor later tonight with the arrival and then passage of the strong cold front potentially gusting past 55 mph or so in the DC-to-Philly-to-NYC corridor…winds will calm down by the early morning before picking up again from later tomorrow through Saturday. This overnight band of rain in the I-95 corridor will not be the end of the precipitation from this unfolding complex storm system.
The snow can be significant during this upcoming storm system in some of the higher elevations locations of the Appalachian Mountains to include the Laurel Highlands of SW PA, central and eastern WV, northeastern PA (e.g., Poconos), and upstate NY (e.g., Catskills and Adirondacks). Map courtesy NOAA, tropicaltidbits.com
With the deepening upper-level trough and developing secondary surface low, “wraparound” rain showers are likely to develop later tomorrow in an unstable atmosphere and continue off and on right through Friday evening. The surface low pressure system will, in fact, rotate around for a period of time as it becomes increasingly influenced by the blocking high pressure stationed to the north over NE Canada.
As colder air wraps into the system, the rain will mix with and then changeover to snow across interior, higher elevation locations. In fact, the changeover to snow is quite likely by Friday all the way into the DC-to-Philly-to-NYC corridor and small accumulations cannot be ruled out in some of the suburbs to the north and west; especially, in those areas to the north of the PA/MD border.
In the higher elevation locations, there can be significant snowfall on the order of 6 inches or more and it is likely to be of the heavy, wet variety with the expected “borderline” temperatures. The higher elevation areas with the best chance of significant snowfall from this upcoming event will include northeastern PA (e.g., Poconos), upstate NY (e.g., Catskills, Adirondacks), interior northwestern NJ, and also back to the southwest in the zone from the Laurel Highlands of southwestern PA to central/eastern West Virginia.
Colder-than-normal weather pattern sets up for late November/early December across much of the nation. This forecast map from the 00Z EPS (Euro ensemble) features large area of below-normal temperatures for the 5-day period from 30 November to 05 December. Map courtesy ECMWF, weathermodels.com, BAM Weather (X)
Looking ahead, a wintry weather pattern is shaping up with other cold shots to follow this one as we progress through the last part of November and into the early stages of December. There are likely to be additional snow threats as well perhaps even one later next week around Thanksgiving Day...let the games begin.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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