March 7th-8th 2018 Storm Potential

Good morning.  Lets begin with a brief discussion on the differences between the March 7th-8th set up vs the most recent set up on March 2nd.  First notice our surface LP is sitting in approx. the same spot but in this upcoming set up it has been stated that there will be more cold air to work with. Why?  





Lets take a look at a few things.  I will try and keep it as simplified as possible.  To do so we will look at the surface and the 850mb(5000ft) set up and compare the prev and the upcoming.  

Simply stated the air mass or source regions for the air that will be pulled into the centers of our low pressure vortex at the various levels of the atmosphere will be vastly different.  In both set ups we will have a surface low in similar positions, and a closed 850mb low, 700mb low, and 500mb low in similar positions just south of LI but the atmosphere surrounding them is what will be diff.  Look at the set up for the surface and 850mb levels.  Images will have the March 2nd set up first followed by the 7th/8th







So as you can clearly see that with this current set up the source region is much more favorable for cold air.  You can see by the close up shot of 850mb I showed above the winds were screaming into the coast in the mid levels right off the ocean just absolutely flooding the air mass with warm ocean air.  While it wont be a direct arctic air mass that we are working with we will have a much colder source region from which to draw from given the position and strength of the surrounding features.  

Now lets shift gears to 500mb set up for the up coming system only.  Below is the evolution using the euro but GFS and other globals are pretty similar with the general progression of the pattern.
 
I have outlined the two 500mb feautures that will come together to generate our storm.  There are two import features to look at ahead of the storm.  First notice the HP in the top right and the ULL in the bottom right of all the images below.  Notice that they do not mov at all.  This is our block, plain and simple and is critical to all of this.  Without it we wouldnt be having this discussion.  Second as we head into Mon/Tues (2nd and 3rd image below) we get a reinforcing shot of cold air in the upper levels.  Again not straight up arctic, but colder than what we had pre March 2nd storm without question.  As we head into the Early Wed time frame notice the two upper level pieces of energy begin to interact and phase.  








To reiterate without the block this storm cuts and we get another rant from Jimmy about how awful this winter is.  BUT because there is a block the surface low again trys to cut into the Ohio valley and Nwestern NY, just like the March 2nd, and is forced to transfer to the coast as it runs into the block (the banana HP(because it looks like a banana) to the north).  Its the shape and position of the HP that is why this system has more cold air to work with in along the boundary and low levels.    





This general set up is pretty much uniform throughout all modeling.  However, there are still minor details to be worked out which is what shapes the IMBY results.  Where, when, or if the 500mb low closes off; where is the exact track of the surface low will all be important.  Again the mid level temps should not be an issue even for the coast, unless the track is over LI or west.  The boundary layer cold although much improved over the last system is still a question mark for the coastal plain.  That said a positive for this storm and boundary layer temps is unlike the prev storm where we got started early in the day and got cranking at the peak of the daylight hrs, this system looks to get started mid-day and peak when sun angle shouldn't play as big or any roll if the heaviest comes in at night.   This is an esp important point for the coastal plain.  Lets see what our trends hold over the next 24hrs.  

We Track!!!!!  

And yes it is Banter and yet also not but its awesome none the less

snowday111 wrote:Is this a Tuesday night into Wednesday or a Wednesday night into Thursday scenario?

We’d to Thursday

jmanley32 wrote:Got a chance see the 12z CMC closer now, wow 4 LP from 7th to the 13th, miss us to east including this one, way offshore too, hopefully its not a trend.

Too much blocking. It won’t be OTS like that.

billg315 wrote:
Three things I continue to like about this:
1. System starts with much colder air in place at surface and aloft than last system. Not as cold as I’d like it but better than Friday which actually still worked out for people just to our N&W. Also snow may continue after dark Wednesday which is a better time for accumulation.
2. I like when surface low develops further south (NC/VA) because it gives it more time to deepen and organize as it moves north toward and past us.
3. Unlike last system models seem consistent in general placement of low and cold air. So while coastal areas have mixing concerns (as they always will with March storms) there is at least a little more consensus away from the coast for snow.
Three things I don’t like:
1. A north and west trend as we’ve had this year could kill us with this one. GFS was already a little too close to coast for my liking and produces mix/rain issues NYC east. Any further west and this could be a slop fest at best;
2. This storm may not be as strong do areas that stay cold enough for snow may not be in heaviest precip.
3. During day Wed. even with colder temps we’re still mostly above freezing so stickage at outset is still as Mike pointed out a concern.

Perfect position right now. With the block in place it's going to back west a little

Euro was perfect for me. I’m thinking big picture for everyone.

aiannone wrote:wouldnt a west shift cause the coast to rain? i would have assumed we want it a bit east. less snow but colder

Depends on how far and what time of day is it.