The Return of the 12/5 Snowstorm

[SnowenOutThere]

So, over the past couple days I've been quite the downer on this storm having a possibility of bringing widespread snow to the area. In the past I mainly felt this way as we were relying on a convoluted mess of shortwave interactions. However, in the past 12 hours modeling has moved to put us on a far easier path to victory as they reemphasize shortwave 1 (previously we were using shortwave 3 even days ago) as the dominant way to get precipitation into our area. Of course, it could shift the other way but this is exactly the trend we want to see. Lets take a look at the difference between the past GFS runs that leave us high and dry and the Euro/NAM camp that actually has a real storm. 

This GFS run shows our first shortwave that gets compressed by a combination of factors. We have energy flooding the west (feature 3) and another NS shortwave which really is the main issue (feature 4 note the string of vorticity connecting to feature 3). Feature 2 is just sorta helping with moisture transport and imo isn't overly important. So, we run this forward in time and we see this:

Feature 1 is now basically nonexistent as it is a ribbon of vorticity from Texas to Virginia. So, the real push northward of precip is instead by feature 2 and 3/4 interacting with each other which frankly was never going to workout unless we got a minor miracle (and the thermals would be bad from the extended return flow anyways and was shown by the GFS having rain where there was any precip). It was from this perspective that I believed there was no way we could get a storm into the Mid-Atl

Lets compare to the Euro/NAM:

We already have shortwave 1 way more clearly defined and less strung out. This is what actually causes a storm in this run not shortwave whatever the hell the GFS does! Notice how much simpler this is! its just a shortwave out west moving east into cold air! We can legitimately do that! Of course, features 3 and 4 are still there but they are held back and give us a little more breathing room. 

 

By Friday morning itself the difference is even more clear as there is still a consolidated mass of vorticity and that creates our storm. What we need to look for is for features 3/4 to slow down or dig south at a sharper axis to encourage the first shortwave to consolidate. For instance see the difference between 6z having the energy out northwest of our storm being flat across Chicago and the 12z having it spike north south west of Chicago area and encourage development downstream instead of suppressing it. 

I think that piece of energy is the main thing we have to watch (the Nam 3k has an amazing depiction of how a flatter and faster NS energy will suppress the flow but sadly I don't have the upload space but please go and make one yourself), if it manages to hold back or dig further south while maintaining a good axis I think we're in the game to get a nice snow day Friday. 

 

TDLR: I am no longer Debbie downing Friday. We got a legit shot if the Euro/Nam is right in the handling of shortwave 1 as the primary piece of energy.

 

[Eskimo Joe]

Bring us home @SnowenOutThere. A cold powder event would be amazing, even if it's a 1" - 2" event.

[bncho]

12z EPS is a substantially larger signal than 6z.

[adelphi_sky]

2 minutes ago, Eskimo Joe said:

Bring us home @SnowenOutThere. A cold powder event would be amazing, even if it's a 1" - 2" event.

A weekend snow would be nice so that we can enjoy it without having to work. Hoping it starts after rush hour.

[SnowenOutThere]

45 minutes ago, SnowenOutThere said:

(the Nam 3k has an amazing depiction of how a flatter and faster NS energy will suppress the flow but sadly I don't have the upload space but please go and make one yourself)

Don't know if this will actually embed how I want it to but this is what I mean. You can really see the string of vorticity in the early-middle part of the loop that suppresses the flow to the east (hopefully we get that to trend less intense/further north). Then we can see the second part with the west getting flooded with unconsolidated energy which results in the shortwave collapsing between the flow to the south and the western push. 

https://imgur.com/a/Eloa7k7

[EastCoast NPZ]

I'm pretty pessimistic after today's debacle.

[wxmeddler]

All hail the Dec. 5th magic!

[mitchnick]

Srefs at the end of their recent run. This is just 24hr precip. You can check out other stuff at this Pivotal link.

https://www.pivotalweather.com/model.php?m=srefens&p=qpf_024h-mean-imp&rh=2025120215&fh=87&r=conus&dpdt=&mc=&pwplus=1

[ravensrule]

24 minutes ago, EastCoast NPZ said:

I'm pretty pessimistic after today's debacle.

Shocking, you are NEVER pessimistic. 

[mitchnick]

Accuwx take