Thursday Storm Update: Details Becoming More Clear

Good morning. We are now 3 days away from our potential snow event for some folks which means its time to try to nail out some details. Overall this storm looks to effect our southern zones and just breach by our northern areas.When it is all said and done a moderate snowfall is possible for areas in the Baltimore/Washington and south Jersey regions. To the north there will likely be a cut off.  

The timing of this is Sunday to Monday morning. There looks to be an initial wave of light snow Sunday morning then some more moderate snow for the southern zones Sunday night. I will be ironing out this detail in the next several days.

Here is my preliminary impact map. This will be updated and filled in with more details in the coming days as I gain more forecast confidence. For now its my best estimate of where impacts will be...

I took a middle ground with this map. There are scenarios were I can see this shifting north or south (Which would produce a very light non event).

Lets now take a quick look at the forecast details.

Models are now starting to come into more agreement on a low pressure system that passes to the south of the region...

When I took a look at this setup earlier in the weak it really gave a strong signal for a storm and many factors I liked to see were on the field. Here was my original image...

Good ridge out west, vortex over eastern Canada, energy diving down into the country. All big precursors to a storm. 

Where the wrench got thrown in is with that vortex in eastern Canada being too much of a good thing. It stubbornly drifts too far south which causes the developing storm to sheer off.

For example, by Friday this setup looks great...

Ridge out west, alot of energy looking like its going to consolidate and form a storm...

At this time frame it looks like the big one is approaching. However, due to that vortex drifting too far south, it starts to sheer off the storm, a result of High pressure that is too strong....

Looking above you can see snow is cut off to the north due to too much high pressure. Think of the storm development as being squashed.

The jet stream shows this best with a big area of confluence or air coming together too far south over southern New England (Seen in red)...

So this prevents the big storm from forming and walloping the eastern seaboard.

However, it is not over yet. After an initial wave of light snow that breaks up Sunday morning. Round two is were most of the snow should fall in my target zones. In fact, there till is a chance that we can see further development of a round 2 wave effecting areas more north.

Here is what I mean...

Looking above you see energy in the jet stream and its 4 run trend from the GFS model. This is valid for late Sunday night. Notice how the trend is to sharpen the energy a little and pull it back west. 

This is resulting in a stronger surface low developing Sunday afternoon/night after the initial batch of sheered off snow Sunday morning...

This is the trend we need to watch closely next 2 days. If this energy continues to sharpen further, it would mean the storm is even closer to the coast than I think and this turns from a moderate to a heavy event. It also would mean areas to the north see more snow.

I try to always look were things might go not where they are. 

So thats it for now. There will be frequent updates to come.