Eastern US Bracing for Major Winter Storm

Winter Weather Advisories, Winter Storm Watches and Winter Storm Warnings have been posted across much of the Appalachians, Mid-Atlantic and Southern New England in advance of a potent, early season, Nor'easter that is expected to develop over the next 24 to 36 hours..

The area to be impacted is rather extensive stretching nearly 1000 miles from northern Georgia north to New England and despite being so close in range, models have been struggling to nail down it's path leading to a large forecast descrepancies depending on your source.

Jet Stream Dynamics

One main reason that we have seen the models changing, is because of what's happening "up stairs" in our atmosphere as a complex jet stream pattern takes shape.

As upper level energy from the southern branch consolidates with the existing northern branch of the jet stream, we will see an interesting "phasing" of these winds as the "left exit" region of the approaching southern branch "jet streak" interacts with the "right entrance" of a jet streak already associated with the northern branch.

Models often struggle with this type of set up often either "over phasing" or "under phasing" these features.

Eventual Storm Track

As a result, models today are scrambling to catch up and has resulted in a very notable northward shift in the storm track as a surface low pressure travels across the Lower MS/Lower OH/TN Valleys tonight before transversing the Appalachians while rapidly deepening into the Mid-Atlantic tomorrow/Wednesday night.

So how much snow are we talking about?

That really depends on the exact path and strength of the surface low. However, take a look at just how much has changed just over the last 24 hours. Notice total "liquid precip" amounts via the Euro below.

While total precip amounts on the order of two plus inches of liquid is still expected in the heart of the #SnowZone. The placement has shifted from South-Central PA to North-Central PA since yesterday.

So as far as snow potental, that means that areas like DC and Philly may very well end up on the warm side of this system with significanly lower snowfall amounts. The uncertainty will be even greater into the New York City area where a DRAMATIC snowfall gradient exists. Some models have backed down to several inches for Long Island (See NAM below) with much more robust amounts of a FOOT plus just north of the city. I don't envy forecasters downstate right now.

Further inland across the higher terrain of Central PA and Southern NY could be looking at a real whopping incuding areas like Williamsport, Scranton and Binghamton where ONE to TWO FEET of heavy wet snowfall appears likely at this juncture. This will be a BIG storm for many.

See current Euro for reference below.

So what does this mean for Western New York?

While uncertainty is still high, I think a general 1 to 4 inches appears likely for most along the Lake Counties including Buffalo, Rochester and Oswego with the bulk of this falling Wednesday night. However, further south into the higher terrains of the Finger Lakes I would expect those totals to ramp up quite a bit perhaps on the order of 4 to 6" plus. Totals should be even higher into the Southern Tier with areas near the PA line looking at realistically a FOOT or more.