1:00 PM | ****An active Arctic frontal passage to include rain transitioning to accumulating snow/sleet on Saturday...high winds and very cold conditions on Saturday night and Sunday****
Paul Dorian
High-resolution surface forecast map for mid-morning on Saturday with a changeover to snow (shown in blue) already underway in DC, Philly and on the doorstep in the NYC metro region. Map courtesy NOAA, tropicaltidbits.com
Overview
Many ingredients are going to come together for a very active Arctic cold frontal passage this weekend that will result in rain transitioning to sleet and accumulating snow on Saturday and high winds and very cold conditions for Saturday night and Sunday. There will first be significant accumulations of snow across interior sections of the Mid-Atlantic/NE US on Saturday and then all the way into the immediate DC-to-Philly-to-NYC corridor. Wind gusts of 50+ mph are likely throughout the northeastern quadrant of the nation from later tomorrow through tomorrow night and into early Sunday with downed tree limbs and scattered power outages on the table. The weather will calm down some by later in the day on Sunday, but it’ll remain much colder-than-normal for this time of year and then a warm up begins on Monday.
An upper-level jet streak will be a contributing factor on Saturday/Saturday night in this very active Arctic frontal passage. Map courtesy NOAA, tropicaltidbits.com
Details
After another tranquil and relatively mild day, the weather will turn much more active on Saturday with the approach and then passage of an Arctic cold frontal system. The temperature boundary zone of this strong cold front will become the focus area on Saturday for the formation of surface low pressure. Many ingredients will come together that will contribute to the rapid intensification of this surface low pressure system as it moves along the frontal boundary zone from the southwest to the northeast. These ingredients include strong jet streaks at multiple layers of the atmosphere, mid-level frontogenesis, and a phasing together of vorticity maxima in the southern and northern branches of the jet stream.
Unusually cold Arctic air will flood the eastern states this weekend…way below-normal for this time of year. Map courtesy Weather Bell Analytics (Meteorologist Joe Bastardi, Twitter), NOAA
Ahead of the Arctic cold front, there will be some rain from late tonight into early Saturday morning along the I-95 corridor and temperatures will likely reach their highs for the day at this time. Following the passage of the Arctic front later Saturday morning, temperatures will drop sharply and the rain will transition to sleet and then accumulating snow from west-to-east across the Mid-Atlantic region.
High-resolution forecast map of total snowfall amounts for this upcoming weekend weather event. Map courtesy NOAA, tropicaltidbits.com
Snow will first pile up across interior sections of the Mid-Atlantic/NE US from West Virginia to northern New England late tonight/early Saturday with 6+ inches possible in many of these higher elevation locations. In fact, if you like to ski in northern New England, this storm will make you happy as places like Vermont and New Hampshire should get hit hard with accumulating snow this weekend. Accumulating snow will then reach the immediate DC-to-Philly-to-NYC corridor later on Saturday morning (see estimates below) following the passage of the Arctic front. For a few hours, the weather can get pretty wild on Saturday in the much of the I-95 corridor with intense “frontogenetic” banding generating a combination of heavy snow and strong winds. One other concern is the possibility for a quick “freeze-up” on the roads of any leftover water from the “pre-frontal” rainfall given the expected sharp drop in temperatures.
A low-level jet streak will be a contributing factor on Saturday/Saturday night in this very active Arctic frontal passage. Map courtesy NOAA, tropicaltidbits.com
In addition to the snow and ice, winds will be a big concern this weekend as they’ll intensify dramatically by later Saturday and Saturday night as the surface low pressure system strengthens significantly. A very tight pressure gradient will develop by late Saturday between the departing strong (and still intensifying) low pressure system over northern New England and a strong high pressure system that will build over the southern states. The result of this tight pressure gradient will be wind gusts at 50+ mph from later Saturday into Saturday night and this kind of intensity can certainly raise the possibility of some downed tree limbs and power outages.
The atmosphere calms down some by later Sunday, but temperatures will remain well below-normal for this time of year with afternoon highs generally confined to the 30’s much of the area. Looking ahead, calmer and milder conditions are expected in the eastern US during the first half of next week, but it may be a tough haul to get to that point.
Snowfall estimates:
DC metro region: 1-3” South/East side of DC; 3-6” DC and North/West
Philly metro region: Coating-2” South/East side of Philly; 2-5” Philly and North/West
NYC metro region: Coating-2”
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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