9:30 AM (Sunday) | ***Late week deepening upper-level trough in the Mid-Atlantic/NE US…rain from late Wednesday into early Thursday…windy, colder to follow…interior accumulating snows***
Paul Dorian
Upper-level weather maps will feature a deep upper-level trough of low pressure by late Thursday centered over the Mid-Atlantic region at the same time intense blocking high pressure is situated over northeastern Canada. Map courtesy NOAA, tropicaltidbits.com
Overview
The first half of the new work week will be relatively quiet and mild in the Mid-Atlantic, but the weather turns quite active later this week as a deepening upper-level trough slides into the eastern states. This strong upper-level trough will become a slow-mover thanks to intense blocking high pressure to the north over northeastern Canada. At the surface, an initial low pressure system will head towards the Great Lakes in the late week time period and then a secondary low should form near the northern Mid-Atlantic coastline. The end result of this unfolding scenario will be rain and possible thunderstorms in the Mid-Atlantic region from late Wednesday into early Thursday and then windy, colder conditions to follow for the next few days. Accumulating snow is likely during this event across interior, higher elevation locations of the Mid-Atlantic region from update PA to upstate NY, and interior New England can get hit hard as well by the end of the week.
A supporting feature for the late week deep upper-level trough of low pressure will be a strong jet streak aloft that will be cutting right through the Mid-Atlantic region. Map courtesy NOAA, tropicaltidbits.com
Details
High pressure will generally dominate the scene in the Mid-Atlantic region during the first half of the week, but then a complex low pressure storm system will take control later in the week. An upper-level trough of low pressure will push into the central US by mid-week and then deepen by later Thursday as it slides into the Mid-Atlantic/Northeast US. At this point, the deep upper-level trough will become quite a slow-mover and “forced” to rotate around the northeastern states for a few days thanks to intense blocking high pressure to the north that will be centered over the northeastern part of Canada. At the surface level, an initial low pressure system will push into the Great Lakes region, and then a secondary low will form somewhere near the northern Mid-Atlantic coastline during the latter part of the week.
Teleconnections indices known as the Arctic Oscillation (AO, top) and North Atlantic Oscillation (NAO, bottom) will be sliding deeply into negative territory in coming days which is usually a sign that high-latitude blocking is about to take place. Indeed, intense blocking high pressure will form over northeastern Canada by later this week and it will result in a very slow-moving upper-level trough system over the northeastern part of the US. Plots courtesy NOAA
The end result in the Mid-Atlantic region of this unfolding scenario will likely be occasional rain from late Wednesday into early Thursday and there can be a thunderstorm or two mixed into the picture as a strong cold front pushes through the area. In fact, this is likely to be the most significant rainfall event in many weeks for many spots of the Mid-Atlantic region in what has been an extended period of very dry weather. Scattered rain showers will be possible from Thursday afternoon through the day on Friday as the atmosphere remains quite unstable given the strong upper-level trough that will rotate around the northeastern states for awhile.
Much colder-than-normal air will pour into the Mid-Atlantic region and Northeast US on the backside of strong low pressure during the day on Thursday and this will likely result in accumulating snows across many interior, higher elevation locations from upstate PA to interior New England. Map courtesy NOAA, tropicaltidbits.com
In terms of temperatures, after a mild day on Wednesday ahead of the cold front, it turns noticeably colder on Thursday and it’ll remain quite chilly on Friday and Saturday as well with below-normal temperatures for this time of year. The winds will become quite strong later Wednesday as the cold front approaches and then will stay strong on the storm’s back side from a northwesterly direction. In fact, those strong winds to follow will likely last through at least Saturday and perhaps even into Sunday given the expected slow movement of the overall storm system.
Accumulating snows are likely during this late week storm event across some of the interior, higher elevation locations. This particular forecast map of total snowfall by week’s end comes from the 06Z run of the Euro model and features some significant snowfall across upstate NY as an example. Map courtesy ECMWF, stormvistawxmodels.com
As far as snow is concerned, it should become cold enough on Thursday for some accumulating snow to fall across interior, higher elevation locations of the Mid-Atlantic region from upstate PA to upstate NY and interior New England can receive significant snowfall from later Thursday into the day of Friday. It is not out of the question that some snowflakes be seen all the way down to the I-95 corridor from later Thursday into Friday perhaps mixing in with the likely instability (rain) shower activity.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com