11:30 AM | **Some snow likely across much of northern Mid-Atlantic region from later Friday into early Saturday as inverted trough develops...coldest air mass yet to follow**
Paul Dorian
The predicted low-level wind flow on Friday evening by the 12Z NAM shows where the inverted trough may set up (black line) with generally easterly winds on its east side and northerly winds on its west side leading to convergence (and upward motion) right along the trough axis. Map courtesy NOAA, tropicaltidbits.com
Overview
The combination of a weakening “clipper” low pressure system and an intensifying ocean low that develops an inverted trough will raise the chance of some accumulating snow from later Friday into early Saturday across the northern Mid-Atlantic region to include eastern PA, New Jersey and New York City. Farther to the south, snow showers are possible in the DC metro region by Friday night, but accumulating snow there is less likely than to the north of the PA/MD border. As the intensifying ocean low pulls away to the northeast on Saturday, the coldest air mass of the season so far will ride into the Mid-Atlantic region on stiff northwest winds and the lowest temperatures in this cold snap are likely to occur early Monday morning.
An inverted trough will extend from low pressure over the western Atlantic to the Mid-Atlantic coastline and nearby locations will have an increased chance for some snowfall later Friday into early Saturday. Map courtesy NOAA, tropicaltidbits.com
Snow threat from later Friday into early Saturday
A weakening “clipper” low pressure system will drop south and east at week’s end from the Northern Plains to the Great Lakes and, at the same time, low pressure will be forming over the western Atlantic Ocean. The ocean low will intensify rapidly late Friday as it pushes to the northeast and an inverted trough will extend from the surface low pressure center back to the northern Mid-Atlantic coastline. As a result, there can be rain and/or snow showers early on Friday across the northern Mid-Atlantic region and then snow showers or even a period of steadier snow is possible from later Friday into early Saturday. In fact, some snow accumulations are likely across eastern PA, much of New Jersey, and New York City metro region by early Saturday morning on the order of a coating to a couple of inches.
The best chance for some small accumulations in this late week/early weekend system will be across eastern PA, interior New Jersey and NYC. Map courtesy NOAA, tropicaltidbits.com
To the south of the Mason-Dixon Line, there can be minor accumulations across sections of northeastern Maryland and snow showers are certainly possible on Friday night in the DC metro region, but likely little to no snow accumulation down there.
The coldest weather so far this season will take place on Saturday night, Sunday and Sunday night with early Monday morning lows likely near the 10 degree mark in many of the suburbs to the north and west of DC, Philly, and NYC.
Coldest air yet from later this weekend into early next week
As the ocean low intensifies and pulls to the northeast on Saturday, the coldest air mass so far this season will ride into the Mid-Atlantic region on stiff NW winds. The first of its kind college football playoff game at noon on Saturday in Penn State’s Beaver Stadium will be played with temperatures holding in the 20’s and a stiff NW wind will make it feel even colder than the actual air temperatures. Sunday is likely to turn out to be the coldest day so far this season throughout the Mid-Atlantic region with highs confined to the 20’s in most spots and the lowest temperatures during this cold snap should take place by early Monday morning with overnight lows not far from 10 degrees in many suburban locations to the north and west of DC, Philly, and NYC. Looking ahead, temperatures will moderate by Tuesday (Christmas Eve) and Wednesday (Christmas Day) of next week and another low pressure system could bring some snow, ice, and/or rain to the Mid-Atlantic region from Tuesday into Wednesday.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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