Dec 16 Just a little change can make the difference

Synoptically some players are on the board. Vigorous ULL, significant block around Hudson Bay, 50/50 Low, a western ridge. It's going to come down to how quickly and efficiently the energy transfer takes. The longer and less efficient the more mid-level warmth will occur. Also note mid-level warmth is usually under modelled.

Best chances for snow are NW of I95 with this specifically NW NJ, Hudson Valley and NEPA. It's not far off from being a threat on the I95, but IMO we need the the block be a little tougher resistance on the ULL which will flatten out the trough and mitigate the mid-level warming. Models are starting to show that a bit. Also, note this is not going to be a bomb cyclone because the western ridge isn't ideal.

Beware of snow maps right now too they are going to be meaningless until about 48 hours out with this setup IMO. Let's see what happens here.

Mount Holly NWS good high level overview for end of week.

amugs wrote:Truth right there - I 80 N again - IF we can get this down to the VA Capes or redevelopment of the coastal and traject more NE then we shift the Snow/Mix line further south and a bit more NAO/AO press which it is tending to. Don't underestimate the press as I have been saying. You connect that ridge bridge over the top then watch out underneath! Remember this is mid December - all gravy right now.

The Norm MacDonald rule of thumb says to expect that upper level low to exit the continent at the same latitude it came in. I don’t care what the models say, I expect this to Secondary near Norfolk VA. Big Snow potential for interior Pennsylvania later this week. #wxtwitter pic.twitter.com/35C6j86hSQ

— Mark Margavage (@MeteoMark) December 12, 2022

This is a great post Mugs. This will put this general rule to the test for sure. Unfort there is a weakness in central Canada leading to an area of energy dropping into the back side of our system bringing the ULL too far N. I believe Heehaw or Matty Ice pointed this out. A few scenarios that need to sort out in order for the Norm rule to work. We need to go back to when the ridge conbnected over thge top of us in Canada like it did a few days ago. This would bring the ULL to our south.





Either that or the primary cuts as is currently modeled, but so far N&W that there is a completely separate wave of energy that comes off on the spoke of the original that runs into the potent HP block to our N giving a solid front end thump. Lets see how things shape up over the next few days.

I kind of thought about that, Scott, where if the primary gets to say Wisconsin, it’s not even really a transfer to a secondary anymore. Rather it’s a new low altogether that forms along a front.

This is a CAD signature on 12Z GFS. Note that H in Quebec.  Not retreating or elongating, but remains round.  There will be front end frozen from this in the interior.  Maybe even I95.  IMO.

The trajectory of the mid-level energy is improved.  It's more NE instead of NNE indicative of a track between BM and coast.  Have to see if this is real or just model noise. Synoptically it makes sense to me due the resistance up north, but need to see consistency.

heehaw453 wrote:This is a CAD signature on 12Z GFS. Note that H in Quebec.  Not retreating or elongating, but remains round.  There will be front end frozen from this in the interior.  Maybe even I95.  IMO.

This is exactly it.  This still has a shot and don't discount snow to the coast just yet.  Still a long way off but possible.  As you can see below todays 12z GFS the Low into the N Plains is weaker and further west relative to 06z.  If this trend conts, weaker and further west that would bode good IMO.  





If we can start to trend a little better in the area circled where the HP trends stronger in the are in the circle this would likely lead to the primary weaker and not making as far N and east, AND cause our secondary low to not track quite as close to the coast and further enhance the CAD signature.  A long way to go with this one.  

I'd like to see the Euro come on board with the storm moving more S&E.

12Z EPS or OP not on board with a SE movement.  

The GFS is definitely showing effects of the block more which synoptically makes sense IMO. The issue is the mid-level air mass and how warm it becomes.  This storm isn't going to bomb but if it pulls off shore enough and develops fast enough then it can switch the mid-level winds.  

heehaw453 wrote:The GFS is definitely showing effects of the block more which synoptically makes sense IMO. The issue is the mid-level air mass and how warm it becomes.  This storm isn't going to bomb but if it pulls off shore enough and develops fast enough then it can switch the mid-level winds.  

Totally agree! But that’s why I’m pessimistic. It’s not one uphill battle, it’s several. As you say, we can get a shift to the point where the track is much improved, but the lack of strength then is still an issue. Then THAT needs resolved.

MattyICE wrote:

heehaw453 wrote:The GFS is definitely showing effects of the block more which synoptically makes sense IMO. The issue is the mid-level air mass and how warm it becomes.  This storm isn't going to bomb but if it pulls off shore enough and develops fast enough then it can switch the mid-level winds.  

Totally agree!  But that’s why I’m pessimistic.  It’s not one uphill battle, it’s several. As you say, we can get a shift to the point where the track is much improved, but the lack of strength then is still an issue. Then THAT needs resolved.

Absolutely.  I'm not a fan with the ULL being where it is and the only reason there's a chance is because of the blocking.  It just might not be enough to salvage this for many on this board.

amugs wrote:18Z Euro much colder and NNJ almost all snow and mix this run. Caving to the GFS and NAM. Feeling the CAD, press of the block....don't underestimate the block and cold arctic press with a HP over Quebec and locked in. I can see another tick or two SE.

Yes. There is more consensus on the shift SE.  I noticed RGEM fairly cold too.

Note the ULL location in Iowa when it spins energy around the base of its trough. That's a well defined storm spinning pretty good with a decent ridge to its west.  How it flicks off the energy also will affect where this storm goes.