By now, most have heard of what’s about to happen in southern and central New England – 2-3 feet of wind blown snow with blizzard conditions this Friday and Saturday. This storm will be the biggest in decades for them and will likely shut down that part of the country into next week.
Given the relative lack of snow the past two years in the northern mid-Atlantic, the obvious question for snow lovers – and haters for that matter – is what about us? Can we expect some of the same? Well, the answer is no – not 2-3 feet, and not blizzard conditions for our area. However, there are some things am I following which suggest we still can get a significant to major snowstorm in most of eastern PA and central and northern New Jersey.
Let’s start with the models. The European model has by far been the most consistent, bringing this storm up the coast for the past 10 days now:
Prior to this point in time, it is prudent to look at the upper levels of the atmosphere, at 500 mb, to see whether this models forecast coincides with whats happening in real time. This is the 500 mb map for 4 am eastern time from the overnight run of the European:
I drew over the height lines over the southeast US. I know it’s somewhat difficult to see, but you get the idea of the rather gentle SW to NE orientation of the upper level winds at 500 mb as forecasted by the european at 4 am.
Now let’s look at the real time 500 mb chart (also at 4am):
You can see that the orientation of the upper level winds is sharper, and pointing more up the coast, than out. Yes, it’s not a large difference, but it’s differences like this at the infancy of a storm that can change forecasts down the road.
Now let’s look at the 0z GFS upper air map at 4 am:
Also flatter, in fact a little more flat than the European, and definitely flatter than the current upper level pattern above. It’s no surprise then that the GFS pushes the storm even farther east and offshore when compared to the European (see above) at the same time:
So, we have a current 500 mb (or upper level wind field) which is pointing more up the coast than certainly the GFS forecast at this point in time, but more importantly, the European model, which brings the storm the closest to us. An interesting observation, and one that would favor a storm closer to the coast, and more snow as well, for eastern PA and NJ.
How about the pressure, strength of the low over the northern gulf? You can see that the low is about 1009 mb just SW of New Orleans, LA at 4 am:
Compare this to the GFS forecast at 4am, at about 1012 mb:
and the European at 7am, 3 hours later, with still a low of 1011-1012 mb:
Both have pressures slightly higher than what is actually happening at this point in time. Not a big difference, but something to watch.
And finally, lets look at the current radar at 4:45 AM:
You can see that the southern precip shield is much larger than modeled (compare to the maps above), extending into the western half of Georgia, and even up into Kentucky. Additionally, precipitation to the north and west looks healthier than predicted by both models as well. Moisture is beginning to be drawn into the system from the Atlantic just NE of Jacksonville, FL in the form of thunderstorms.
In summary, we have upper level winds pointing more up the coast than out, favoring a storm track closer to the coast, more like the European model. We have a developing low slightly stronger than modeled. And we we have a more expansile precipitation field than forecasted. I’ll be watching all of these factors throughout the day. Current observations and comparisons with the modeled forecast will be critical. How much snow will we get? I think at least 6 inches is a good start in eastern PA, which includes the Lehigh Valley, with as much as foot in the eastern counties along the Delaware river, especially in northeast PA, and in northern New Jersey, IF things come together just right. Southeast Pennsylvania will see the least, with perhaps 3-4 inches in the city of Philadelphia an it’s immediate suburbs. Southern NJ and Delaware will see very little. These numbers can and will probably change, but regardless, this will be the biggest storm of the year for many here.