****Accumulating snow across eastern PA, New Jersey, and NYC from late Sunday into Sunday night...upward motion, dynamical cooling, and an upper level jet streak to play big roles****
Paul Dorian
A key player in the late weekend storm will be an upper-level jet streak centered over the northeastern states which will lead to strong upward motion in the Mid-Atlantic region. As a result, dynamical cooling will likely result in a changeover to all snow near and to the north of the PA/MD border and accumulations of at least a few inches are on the table across much of eastern PA, NJ and the NYC metro region. Map courtesy NOAA, tropicaltidbits.com
Overview
If you have the dynamics (a.k.a. upward motion), the precipitation will follow…
A storm system that came ashore in California at mid-week will cross the southern states today and then spread its precipitation shield into the Mid-Atlantic region from later Sunday into Sunday night. The air mass will initially be only marginally cold enough to support snow; however, dynamical cooling in the atmosphere associated with a strong upper level jet streak should result in much more favorable conditions for snow by Sunday night across eastern Pennsylvania, New Jersey, and New York City with at least a few inches on the table. To the south of the PA/MD border, rain is likely to be the predominate precipitation type in the immediate DC metro area with no accumulations expected. However, snow and/or ice can mix in across some of DC’s northern suburbs, and the northern part of Maryland that is close to the Pennsylvania border can certainly see a couple of inches of snow.
While precipitation may begin as a rain and snow mix to the north of the PA/MD border, dynamical cooling in the atmosphere should result in all snow across much of eastern PA, NJ and as far north as the NYC metro by later Sunday night. Primarily rain will fall in the DC metro region, but there can be a mix of snow and/or ice in some of its northern suburbs and northern MD can certainly see small snow accumulations. Map courtesy NOAA, weathermodels.com (Dr. Ryan Maue, X)
Details
Low pressure pushed through California at mid-week and will cross over the southern states today as it heads in a general eastward direction towards the Mid-Atlantic coastline where it’ll reach by early Monday. There will be beneficial rainfall today across the Deep South and even some severe thunderstorm activity could develop late today in the zone from eastern Texas to Louisiana to southern Mississippi.
Low pressure will likely be situated just off the Mid-Atlantic coastline by early Monday with precipitation winding down across the Mid-Atlantic region. Map courtesy NOAA, weathermodels.com (Dr. Ryan Maue, X)
On Sunday, this low pressure system will continue to head in a general eastward direction - riding along the southern branch of the jet stream - and it’ll head towards the eastern seaboard. The moisture shield will extend northward into Mid-Atlantic region by later in the day on Sunday with only marginally cold air in place to support frozen precipitation…at least during the initial phase of the storm.
Breakdown in the Mid-Atlantic region
To the south of the PA/MD border…
it looks like rain will be the predominant type of precipitation in the immediate DC metro region with no accumulations expected; however, there is the chance for some mixing of snow and/or ice across some its northern suburbs during the latter stage of the storm. In northern Maryland, there can be a couple inches of snow accumulation; especially, in those areas close to the Pennsylvania border.
To the north (and east) of the PA/MD border…
Dynamical cooling in the atmosphere will result in enhanced upward motion and an increased chance of accumulating snow across much of eastern Pennsylvania, New Jersey, and the NYC metro area. The dynamical cooling will be associated with an upper-level jet streak that will produce strong lifting in those areas to the north and east of the Mason-Dixon Line.
Snow accumulations on the order of a few inches are on the table across much of eastern PA including the Philly metro, New Jersey, and likely as far north as the NYC metro…and there can be isolated higher amounts. The bulk of the snow accumulations would take place the nighttime hours since the initial burst of precipitation on Sunday afternoon could feature a mixture of rain and snow which should then change to all snow during the overnight hours. The storm pulls away from the coast on Monday morning leading to a moderately cold President’s Day holiday.
Stay tuned to arcfieldweather.com for updates…a very dynamic storm system.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com