STARDATE 201812.02 

Before the main event this coming weekend ... you should be aware that there is going to be a strong upper air disturbance in the jet stream which will sweep through Tennessee ...North Carolina ...and Virginia on Wednesday, December 5. Several days ago the potential exists for this upper air disturbance to develop a surface LOW pressure area over eastern North Carolina that would produce a period of moderate snow over portions of Virginia ...West Virginia ...Maryland ...and Delaware. That surface LOOW is stll l going to develop but it will do well to the east out in the Atlantic Ocean.     However the upper air energy is still quite strong and the various weather models are showing numerous moderate snow showers over West Virginia ... western Maryland ..portions of the Shenandoah Valley and central and northern Virginia on Wednesday, December 5. Some other models are even showing trace to 1 inch snow amounts over a few locations -- especially in the Shenandoah Valley and western Maryland.

The various weather models late Saturday evening and early Sunday morning were moving into somewhat better agreement. Those of you would have followed WxRisk over the years know that when it comes to East coast winter storms I am not a fan of the operational regular GFS model beyond 84 hours. The model has for years has serious problems in handling the interaction between the northern jet stream (which provides the cold air) and the southern jet stream (which provides Low pressure development and the moisture).
This image shows exactly why I don't like the GFS model. To see this sort of huge variation over the course of 18 hours tells me that the model has no clue. Fortunately there is a new and improved version of the G S model which takes over officially on January 1, 2019.

This new version of the GFS model is known as the GFS FV3. It us vast improvement over the operational "old" GFS.  For example the  Saturday 18z GFS FV3 brings in a tremendous snow/ ice storm for much of western North Carolina .. and heavy  snow for central ...western ..and northern Virginia ...eastern half of West Virginia and much of Maryland for DEC 8-9. This is in strong agreement with the Saturday afternoon European model.

The early months Sunday morning data is also impressive with regard to this event for next weekend. This image shows the operational European model and how it takes the LOW over Hatteras and out to sea. That sort of track ...with the LOW pressure area tracking from Georgia to Cape Hatteras and then out into the open Atlantic Ocean ...is a classic track for big North Carolina Virginia Southern Maryland snowstorm. Indeed the snowfall map from the European model is extremely impressive with huge snow fall amounts over the Virginia Piedmont ... northwest North Carolina all the Shenandoah Valley ...up into Washington, DC and western and central Maryland. Some of this is probably ice or sleet mix in but it is a significant if not major snowstorm especially for early December

This image shows the track of the European ensemble and as you can see the vast majority of the data does support the LOW pressure area tracking over Cape Hatteras and out to sea. IF  correct  IF   this would be a miss  from  PHILLY TO BOSTON

This impressive track is supported by the 6z GFS FV3 model as well as the GFS ensemble.

the 12z SUNDAY Canadian Model is also much further south and east and hence more snow for nw NC VA / DCA.

It should be noted that right now the trend is not taking the snow north of the Pennsylvania Maryland border. That being said it still too early to say this definavtvely. The potential still exists for significant accumulating snow to get into southern Pennsylvania New Jersey and perhaps as far north as NYC. But right now the model trend and data does not support the significant snow of the north of the Pennsylvania Maryland border

12z SUNDAY DEC 2 MODELS

For some of you who are weather wise or weather model Savy and track these various weather models.... then you know that the midday Sunday ( 12Z ) weather models have shifted south - ALL of them ... with the track of the LOW pressure area. The models continue show this to be a significant area of LOW w pressure but because the track of these 12z whether models are further south the snow shield is significantly further south.

For example the operational European model has the system so far south that there is no significant snow north of Richmond. Taken verbatim this to be a historic snowstorm to western half of North Carolina However the European ensemble does not support that sort of shift to the south.

As I discussed above the Canadian models also further to the south and has a lot more snow and Virginia where is yesterday's run it had much more rain from Virginia to Boston .
Even the much improved GFS FV3 model has also shift to the south by a significant degree.

Clearly the fact that all these models have shifted south it means that the models see something in the atmosphere which was not there early on Sunday morning or the Saturday evening models. Tis missing piece of something obviously impacting the track of the LOW pressure area on the southeast US coast for next weekend. . Now that does not mean that this SHIFT SOUTH on these various weather models is permanent or that it wont correct itslef but clearly something is going on which was not on the model yesterdays.