Normally I would have issued the LAST CALL about 8–12 hours earlier but the last 24 here at WxRisk have been rather hectic with a lot of new clients and signing up so I have been running a little behind the eight ball.
However, it is time to put this one to bed and see what exactly will happen. I am pretty confident about this forecast because I have been ahead of the curve on this one for quite a while. When you are dealing with the MILLER B type of winter storm (one LOW pressure area in the Ohio Valley that dies off / weakens and a Second LOW develops on the Middle Atlantic Coast) you will often see the TV meteorologist or the guy on the radio or on some weather site talk about what happens if the coastal LOW tracks further off the coast and it pulls in colder air …” this could lead to a lot more snow” .
But in this event, I have known for a long time that the coastal LOW that is going to form in the southeast US… is going to track on the coast AND inland. This destroys any chance off frozen precipitation from Boston Washington to Richmond. And the temperature maps clearly reflect that both at the surface and at the mid-levels of the atmosphere. The mid December Ocean water is still relatively mild so any kind of east will send “mild “air blasting into the coastal areas Thursday, Thursday night, into Friday morning.
That being said, this first big winter storm for the Mid-Atlantic and New England regions does have its interesting points. In looking at the short-range models at 12Z an 18z and even briefly glancing at the new 0z Thursday model guidance, the one thing that stands out is that the snow amounts in places like the Hudson Valley and the Connecticut River Valley in New England are going to be dramatically lower than the snow amounts on the nearby hills and mountains of New York State, western Massachusetts and Vermont and New Hampshire. All you have to do is look at and understand what the snow maps are actually “saying”.
And when you do that, you will see that the snow maps show a stunning gradient of snowfall.
In the Shenandoah Valley area as well as the western half of Maryland and the eastern third of the West Virginia Panhandle, the ice red looks minimal. The model data continues to run warmer, so temperatures are barely around 32 degrees at dawn Thursday through noon. This means that any icing that forms is going to be mostly on the coldest surfaces and these areas are not looking at a significant ice storm. Some icing yes of course. But it’s not going to be nearly as bad as what it was looking only 24 to 36 hours ago.
The big area that could see the significant ice storm will be interior south central and southeastern Pennsylvania. Temperatures tonight already around 30 degrees with dew points around 20° so the air is quite dense and cold and the ice here is likely to accumulate in the suburbs of Philly, interior Northern New Jersey, the Lehigh Valley into Harrisburg Gettysburg down towards the Maryland border. This is the area that could see a significant ice storm in my opinion.
One last point. — I was planning on doing a video tonight, but I am too damn tired, and I still have commodity Grain weather to do. I will state however for the record that I still believe that the threat for December 22–23rd in the Middle Atlantic and New England winter storm is still there. The last few runs of the GFS are constantly going back and forth with the coastal LOW re-developing and the primary Low coming out of the Great Lakes on the arctic cold front. The operational European is also having problems with this. So again, if you want to understand what the risk / threat is just before Christmas on the East Coast you need to look at ENSEMBLE — not the operational models.
When you do that, you will see that the temperatures are going to be plenty cold enough for snow even near the coast in the Middle Atlantic — even in coastal Virginia the Delmarva and in New Jersey and that the system on December 22nd 23rd and the one on December 26th 27 both have potential to be significant winter storms.
This image is from the 12z European ensemble. the red numbers represent various possible low-pressure areas according to the model and as you can see there is a distinct cluster of significant activity on the Middle Atlantic Coast on December 22–23
and DEC 25–26
