During the past several days there has been persistent indication from the European and the Canadian models that a moderate-size early-season winter weather event is going to develop across the Ohio Valley and portions of the Middle Atlantic and southern New England on Sunday night November 28 into Monday morning November 29. WxRisk has mentioned this event several times on our website and on the Twitter page. Most of the other well-known sources for weather information in social media and on the internet are not mentioning this event at all. The primary reason for this is because the well-known GFS weather model which is very heavily relied upon and easily accessible through the internet, as consistently shown no development at all in the Middle Atlantic region of any significant LOW pressure which might produce rain and or snow or some combination thereof.

Let’s take a look and see what is happening and what the possibilities are.

This image from Monday afternoon’s version of the European model that shows the Upper air or 500mb pattern. I have highlighted a couple of important features on these two maps. Note that there are two pieces of energy in the jet stream pattern which we have designated Z and X (which in the weather business is referred to as “short waves”). X is located in ILL and Z in far northeast Minnesota. The reason why the European model has been very strong with the system is because it is taking these two important pieces of energy and phasing them into a massive system that undergoes explosive intensification as it moves into Virginia and off the coast on Monday (see the image on the right).

At the surface, the Monday afternoon European model produced this kind of weather map. The light blue represents light snow and the darker color blue represents moderate snowfall. Note that there is LOW pressure on Sunday afternoon in eastern Kentucky and light snow falling across much of Ohio, West Virginia, and southwest Virginia that is spreading into central and northern Virginia as well as into Pennsylvania. By early Monday morning, the LOW pressure area is off the coast and there is moderate snow falling in central Virginia in and around Richmond, Charlottesville, Fredericksburg, Washington DC and Baltimore. In this situation, light to moderate snow to reach as far north as Philadelphia and central or northern New Jersey. The European model shows at least a few inches of snow in central and northern Virginia as well as the Shenandoah Valley, western Maryland, southwest Virginia, and most of West Virginia.

As impressive as this map and scenario appears to be, keep in that it is just one model solution. The Canadian model has something very similar but the merging of the two pieces of energy is a little different on the Canadian model which results the surface LOW pressure area forming a little further to the north so that the snow falls mostly in Pennsylvania, New Jersey, coastal New England and southern half of New York.

The GFS model is vastly different because the model completely mis-handles these two pieces of energy which were not nearly as strong on the GFS model. This is the Tuesday midday operational GFS model run and as you can see it has no LOW pressure of any significance near the coast for Sunday night. By the time the surface LOW develops, the system is well off the coast and doesn’t do anything. The 12z Tuesday GFS solution is clearly bogus.

This image shows the upper air or 500mb map from the Tuesday afternoon European model. The model continues to show the two strong pieces of energy in the jet stream which we designate Z and X. These two pieces of energy slam into each other because of a blocking pattern in the jet stream in the southeast Canada and Greenland.

This results in a surface LOW pressure area developing which brings light to moderate snow to eastern Ohio, the southern half Pennsylvania, New Jersey, West Virginia, northwest Virginia, portions of the Shenandoah Valley, and perhaps even southwest Virginia and portions of the Virginia Piedmont.

We can see this on the Mid-Atlantic surface maps from the Tuesday afternoon European model. Notice that the best snows are generally in West Virginia, eastern Ohio, the southern half of Pennsylvania, and perhaps into western and central Maryland and the Shenandoah Valley.

The European model is implying 2 portions to this event. There are two distinct pieces of energy swinging through the Middle Atlantic region on Sunday night. The first piece of energy is centered along the Delmarva Coast followed by an even stronger piece of energy in Eastern Kentucky. The first portion that comes through on Sunday morning followed by a second piece of energy on Sunday night into Monday morning. It is the second piece of energy which could bring snow into Charlottesville and northern Virginia as well as southwest Virginia. We can see this by looking at the European model upper air pattern in high resolution focused on the Eastern CONUS.

At this time only the areas above 1000 feet in elevation would have anything to worry about regarding accumulation.

Finally, the early Wednesday morning GFS model) 00z run) has done a complete reversal and now shows a moderate early-season coastal LOW that brings light to moderate snow to Ohio, West Virginia, Pennsylvania, New Jersey, New York City, and interior portions of Southern New England. This is a big flip from the previous runs of the GFS model and shows once again the general superiority of the European model on East Coast winter storm threats beyond 72 hours.

There is of course some uncertainty with regard to how the surface LOW is going to develop and what sort of track it will take. A track further to the South means more snow in DC- BAL, Charlottesville, Fredericksburg, and possibly even into Roanoke and Richmond. A surface LOW track to the north would mean the snow will be in Pennsylvania border northward into New York City and southern New England and perhaps only snow mixed with rain in DC and Baltimore and Northern Virginia.



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DT Wxrisk

DT Wxrisk


Meteorologist ... Atheist.. Dyslexic ..Baseball.. Fat tail distributions ..Good Judgement Projection… Black Swans/ Taleb …Choas / non Linear Dynamics… ENTP