TUES 945PM VENING UPDATE on Thursday and Friday PM/ Saturday AM SNOW FOR MID ATLANTIC

STARDATE 20220.19….. 2120 EST

BOTTOM LINE — Thursday snow in N Va MD DEL se PA and NJ looks good

Friday night Saturday — BEST snows heavily favored in se third of VA / Delmarva central NC… Richmond metro Norfolk metro Raleigh metro. good shot at 6 inches +… if the snow ratio is really 14:1 or 15 :1 could be a lot of 8–12 inches in those areas. Some accumulating snow in DC BAL VA Piedmont sw VA …. maybe into Philly NYC .. maybe not

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First with regard to Thursday the new data out this afternoon and early this evening, it clearly shows that the best snow associated with the arctic cold front on Thursday is going to fall across New York City, all of New Jersey, southeast Pennsylvania including Philly, Delaware, most of Maryland, the Northern half of Shenandoah Valley, northern half of Virginia. In this area, the snow amounts could be 2 or 3 inches because the snow begins at or before Dawn. The moderate snow bands weakens by the time it gets into central and eastern Virginia including the Richmond Metro area as well as the Middle Peninsula and Northern Neck — and it almost completely falls apart by the time it reaches Hampton Roads

FRIDAY NIGHT/ SATURDAY AM

And looking at the 18z various weather models we are seeing more agreement here.

The operational GFS is pretty much unchanged from the 6z and 12z as it shows the best snows Friday night into Saturday will be located in southeast Virginia and Northeast North Carolina. However, Just like the 12z GFS ensemble the 18z GFS ensemble shows a more robust system with the north edge of the snow shield reaching into northern Virginia as far north as the Pennsylvania Maryland border and southern New Jersey.

The 18Z GFS ensemble precipitation output is close to 12z GFS ensemble: It shows a nice swath of 0.50–0.80” liquid equivalent in the eastern half of NC / southeast third of Virginia and southern Delmarva. At the normal 10 to 1 snow ratio this should produce a very nice 6–9 inches snowfall in this area and a a 2–6 inch snow in central North Carolina …western Virginia…central Maryland… up into Philly and southern New Jersey. And that is exactly what the 18z GFS snow output shows. But if we are looking at a 14 or 15 to 1 snow ratio than that 0.58” of liquid that falls in a 24-hour period at say Richmond (ending as of 1 p.m. on Saturday) is the going to end up producing 9 inches of snow in Richmond and Raleigh and 10 + inches Williamsburg to Rocky Mount.

The snow shield is a little deeper and heavier on the 18z GFS ensemble and the output has gone up in eastern and southeastern Virginia across the Delmarva into Southern New Jersey.

The big news has to do with the last couple of runs of the operational European and the European ensemble. Both of them have moved away from the massive snowstorm that they were showing early Tuesday Morning.

The 12z operational run took the LOW further east but it still had a respectable 8 to 15 snowstorm on the coastal areas of NJ to eastern Virginia to northeast North Carolina. But the 12z euro ensemble QPF and snow out ut came down

The 18z Euro ensemble looks close to what the 18z GFS ensemble is showing
(18z GFS ensemble above) and the snow output is also remarkably close — perhaps a little heavier. The 18z euro ensemble has a 6–9 inch snow from Richmond to Hampton Roads and into the Middle Peninsula. Northern Neck and lower Virginia Eastern Shore. If we adjust for snow ratio then this could be more like an 8 to 12 inch snow band and that would also mean places such as Philadelphia Dover Baltimore DC Charlottesville Fredericksburg Lynchburg would end up with something close to 3–6 inch snow which all seems quite reasonable to me.

This image is a look at the individual model runs from the 30 member 18z GFS ensemble. I have marked some of the outputs with the initials NC = North Carolina to show when a particular member has a North Carolina snowstorm. The initials MA shows a snowstorm that hits the Mid-Atlantic region (as well as Central Virginia). In the breakdown we can see 10 outcomes for the Middle Atlantic and 10 NC outcomes.

Finally looking at the 50-member European ensemble there is a much stronger signal for it bigger snowstorm in Virginia and the Mid-Atlantic.
Here I use 3 codes
VA — Possible big Virginia snowstorm
MA= possible Mid Atlantic
SE = a snowstorm for southeast VA/ eastern NC .

The 18z European ensemble shows 23 out of 50 with a significant Virginia snowstorm and 12 of 40 Mid Atlantic snowstorm

SUMMARY

The data continues to show a significant snowstorm coming for Friday night into Saturday after the Thursday snow for a good portion of Northern North Carolina. central and eastern Virginia Southern Maryland and the Delmarva. The 18z GFS and Euro ensemble are moving towards agreement.

There is no evidence that this LOW is going to track Inland — if anything the concern is that a might slide further off the coast and restrict the Snows only to eastern North Carolina … southeast Virginia …and the Delmarva. I do think that there will be several hours of light to moderate snow even in the interior portions of western North Carolina the Western half of Virginia into central Maryland and southeastern Pennsylvania and probably up into central NJ but that is still somewhat uncertain.