12:00 PM | ****Major storm to bring flooding rains, heavy wet wind-whipped snow, sleet and damaging wind gusts to the Mid-Atlantic/Northeast US with widespread power outages a serious concern****
Paul Dorian
Maximum wind gusts expected for the upcoming major storm with 51-60 mph in the DC-to-Philly-to-NYC corridor; source NOAA
Overview
A major storm will throw just about everything imaginable to the Mid-Atlantic region and Northeast US on Friday and Friday night with the potential for flooding rains, heavy wet wind-whipped snow, sleet and damaging wind gusts. The threat for widespread power outages exists on Friday and Friday night throughout the DC, Philly and NYC metro regions with 60+ mph wind gusts quite possible. This storm will have an impact on the I-95 corridor for an extended period of time due to very strong high-latitude blocking that has set up to our north. As a result, the storm will run into an “atmospheric brick wall” near Cape Cod, MA and rather than taking the usual track for a nor’easter off to the east of Maine, it will be forced to the south and, in turn, impact the weather around here all the way from later today into early Saturday.
NOAA's National Weather Service (NWS) has issued all kinds of watches/warnings for the Mid-Atlantic region to prepare for the upcoming storm. On this kind of map, lots of colors is not a good thing. Courtesy NOAA/NWS
Extreme winds
Low pressure will undergo rapid intensification on Friday over the western Atlantic Ocean and this will tighten the pressure gradient field surrounding the storm which, in turn, will result in extreme wind gusts of 60+ mph in much of the Mid-Atlantic region including DC, Philly and NYC. Widespread power outages are a real concern throughout the I-95 corridor during this storm given the expected extreme winds and saturated grounds from recent rains which tends to weaken the root support system for some trees. In addition, in areas where heavy, wet snow does fall, the threat of power outages will be even greater as the snow will cling to the wet tree limbs and weigh them down.
A loop of surface forecast maps from the 12Z NAM for the next 48 hours (snow in blue, rain in green); maps courtesy NOAA/EMC, tropicaltidbits.com
Rain, snow, elevation and dynamics
Rain will overspread the I-95 corridor later today and early tonight continue through the night as an initial low pressure system moves through the Ohio Valley (heavy snow in southern MI, northern OH) and then gives way to developing low pressure off the Mid-Atlantic coastline. In terms of snowfall, two factors will play a key role in this late season storm: dynamics and elevation.
The track and intensity of the upper-level low during the next 24-36 hours will be a key to pinpointing the areas with the best upward motion (dynamics) and coldest temperatures aloft. In areas near and just to the north of the track of the upper-level low, there will be strong upward motion and the “dynamics” in the atmosphere will act to cool the air and increase chances for accumulating snow on Friday and Friday night. Small-scale (aka, mesoscale) bands of heavy snow may form on Friday with the expected strong dynamics associated with this storm resulting in quite variable snowfall rates over a given small region at a particular time. The location of these potential mesoscale heavy snow bands will realistically be quite difficult too pinpoint until sometime tomorrow. The 12Z NAM forecast map at 500 mb places a closed-off upper-level low over the Delmarva Peninsula/southern NJ on Friday morning and the predicted track and strength of this would favor snow in areas like eastern PA, NJ and NY and perhaps a little can fall as far south as the Delmarva Peninsula and just to the north and east of DC.
The track and intensity of the upper-level low is crucial in this setup for determining areas with the greatest chances for accumulating snow. Typically, areas near and to the north of a closed-off upper-level low have the best chance for snow where upward motions are strong and temperatures are colder. The 12Z NAM forecast map at 500 mb for tomorrow morning shows the upper-level low positioned over the Delmarva Peninsula/southern New Jersey; map courtesy NOAA/EMC, tropicaltidbits.com
As the ocean storm begins its push to the south on Friday from off of the New England coastline, colder air will drop to the south and east and the changeover of rain-to-snow will also push to the south and east. Southern NY, upstate PA, NW NJ will be the areas to first experience the changeover to snow and significant accumulations of heavy, wet snow are likely in these particular areas; especially, in the normally colder higher elevation locations such as the Poconos (PA), Catskills (NY) and NW NJ. In fact, with the tremendous dynamics expected during this storm, it wouldn't be a surprise to see some high spots in southern New York State, northern PA and NW NJ to end up with 1-2 feet of snow.
The changeover from rain-to-snow will then likely continue to sweep south and east from upstate PA, southern NY and NW NJ and it is likely to be snowing by later in the day as far east as NYC and as far south as Philly and central/southern New Jersey with a few inches possible in all of these areas. There is even a good chance in NYC, Philly and central/southern New Jersey for a period of blizzard-like conditions later tomorrow with snow and strong winds occurring at the same time.
12Z NAM total snowfall estimate for the upcoming storm; map courtesy NOAA/EMC, tropicaltidbits.com
Looking ahead
One final note, as part of the overall pattern change across the Northern Hemisphere in recent days, there has been extreme cold in much of Europe and also strong storms there with accumulating snow as far south as Naples, Italy where they haven’t had this much snow in the past 50 years. The overall stormy weather pattern looks like it will continue in Europe and in the US through at least the first half of March. In fact, we may have to deal with another storm near the US east coast next week (~March 7th or so) and then another one a few days after that and yet another one a few days after that.
Stay tuned…the first half of March is going to be quite interesting
Meteorologist Paul Dorian
Vencore, Inc.
vencoreweather.com
Extended video discussion on the upcoming major storm: