December 20-21, 2024 | NE / Mid-Atlantic Clipper & Inverted Trough

[Penn State]

We Are! Penn State! …On Saturday 12/21 Beaver Stadium will host its first ever College Football Playoff matchup between the Penn State Nittany Lions and SMU Mustangs. It’s a White Out game too.. Oh, the irony.. if white-out conditions make an appearance at field level, to accompany the 110,000 fans adorned in white! Mother Nature must be a Penn State fan if college football tradition and winter weather can intersect in Happy Valley 😄 …Now, this won’t be the first meeting between PSU and SMU. That occurred on January 1st, 1948 as the two met in the Cotton Bowl as undefeated teams. Following a 13-13 tie, the teams remained undefeated. So.. what does this have to do with anything? Admittedly.. not much! 😜 But.. those that know me, know I like historical storms.. so I was curious if there were any notable storms that occurred around the time of the 1948 Cotton Bowl. As a matter of fact, there was! The Great Blizzard of 1947 impacted the Northeastern U.S. in late December of that year, a few days before the first clash between PSU and SMU. At the time, it was considered one of the largest storms since the Great Blizzard of 1888. So.. I’m going to call it an omen. White-Out Conditions for a White Out game. A Great Blizzard prior to each team’s first meeting.. and maybe.. another Great Blizzard for each team’s first ever CFP meeting! 

This speculative threat has some favorable indicators, especially on the EPS, GEFS, and CMCE. When looking at the 500 MB Height Anomaly, you can see a clear storm signal for the timeframe around December 21st. However, the MSLP members aren’t consolidated enough to give much confidence in any particular track. The teleconnections are mixed. The -AO and +PNA are favorable, but.. the NAO is positive, which places a question mark around blocking. There’s also the lack of 50/50 low, which is an unfavorable feature. The MJO is in unfavorable phases 5 and 6.. which really does provide pause on this potential. There is a connection with the North Pacific for this timeframe.. with a clear storm signal from December 3rd, which should be.. and is reflected about 17-21 days later. The ECMWF-AI has actually been a leading indicator for this speculative threat, and has had above average accuracy (Ex. Hurricane Milton).

It’s admittedly a bit early.. but with the most recent wind, rain, and wintry threat wrapping-up, this at least provides something intriguing to discuss! I’ve included the 18z GEFS 500 MB Anomaly for the timeframe 12/20-12/22, along with the ECMWF AIFS and GFS GraphCast. All additional details are in the spoiler. 

Happy Tracking! 🤓

Model Guidance | MSLP Surface Map (Hours 204-276) 

12z ECMWF AI 

12z GFS GraphCast 

Ensemble Forecast | 500 MB Height Anomaly 

18z GEFS (12-10) 

Spoiler

Operational Model Forecasts | Surface & 500 MB Vorticity (Hours 204-276) 

12z ECMWF

12z GFS

12z GDPS

Ensemble Forecasts | 500 MB Height Anomaly & MSLP Members (Hours 204-276) 

EPS

GEFS

CMCE

Teleconnections 

MJO Forecast 

AO Forecast 

NAO Forecast 

PNA Forecast 

North Pacific | Bering Sea Rule (BSR) 

WPC Forecast | Day 7 

Edited December 20, 2024 by Penn State

[MaineJay]

The answer might be in there. In all seriousness, reasonably good consistency with the southern stream (doesn't ensure accuracy). Can the northern stream get any depth, and drop something in the pocket at the right moment? 

Inquiring minds want to know. 

 

[losetoa6turbo]

Day 10ish Gefs showing a big indication of a cutoff low forming somewhere.  Hopefully over the mid Atlantic 🙂

 

[Penn State]

3 minutes ago, MaineJay said:

The answer might be in there. In all seriousness, reasonably good consistency with the southern stream (doesn't ensure accuracy). Can the northern stream get any depth, and drop something in the pocket at the right moment? 

Inquiring minds want to know. 

 

lol.. 😂 Somewhere in all that chaos, right?  I was looking at the 12z GDPS and ECMWF 500 MB.. and to be honest, both had a similar look and players on the field. The cutoff low (or piece of energy) is out in the North Pacific in about 84 hours or so from what I could tell. I’ll say this.. the theme this year seems to be expect the unexpected. All of the long-range was warm until it wasn’t. We had a great cold pattern.. until it didn’t produce. Well, the lead-up to Christmas doesn’t look great… Until it does? Or at least.. One can dream, right? lol 

Also.. side note.. I had to make this thread. With my call sign being Penn State.. and this potentially impacting their first home playoff game in the CFP. If this happens, and PSU wins.. Saturday 12/21 will be a highlight reel day for like.. life.. lol 😂 

[Pghsnow]

12Z AIFS.  I want it to be snow showery and be very cold for the PSU game, but I don't want a snowstorm for the game. 

[Snowadelphia]

9 hours ago, Pghsnow said:

12Z AIFS.  I want it to be snow showery and be very cold for the PSU game, but I don't want a snowstorm for the game. 

I’ll be out there too. This wouldn’t be ideal for sure. 

[Penn State]

ECMWF-AI.. So, when I look at the globals.. The European was more of a cutter, the American was more out to sea, and the Canadian was an apps runner, and all of them have been scatter shot for the most part. The AI has certainly been variable, but to my eye, it's been more consistent. Here's the 00z.. and maybe the 06z, which is running now, will be different.. but right now, I'm liking the AI. 

[Penn State]

The 06z ejected the cutoff low more quickly.. and handled the energy differently. The timing of those things, of course, quite important lol.. but the AI made that last post look over cooked lol.. But hey, fun to watch. 

[Penn State]

Just documenting the 12z runs so far.. A number of pieces of energy, but not that great at consolidation. OTS. 

GFS (500 MB)

GDPS (500 MB)

[Penn State]

No lack of action on the 12z ECMWF.. It's almost a 2 fer'.. Little warm, lotta juice. 

[Penn State]

Well.. this just feels wrong to post. Might as well throw darts.. but the CFS supports. 🤦‍♂️

[Pghsnow]

[Pghsnow]

[MaineJay]

1 hour ago, Penn State said:

Well.. this just feels wrong to post. Might as well throw darts.. but the CFS supports. 🤦‍♂️

Go shower up

[Penn State]

24 minutes ago, Pghsnow said:

That AI.. It’s at it again! It’s a good test of the AI too. If it’s right, adds to its credibility. 

[Penn State]

4 minutes ago, Penn State said:

That AI.. It’s at it again! It’s a good test of the AI too. If it’s right, adds to its credibility. 

Just looking at this again.. even has a little stall there too! It showed that this morning I believe. 

[Pghsnow]

2 minutes ago, Penn State said:

Just looking at this again.. even has a little stall there too! It showed that this morning I believe. 

Temps low to mid 20's game time. Still long ways to go to sort this out though.

[Pghsnow]

Could challenge for worst conditions ever for PSU game...  I was at that ND game in 1987. It was brutal. 

https://onwardstate.com/2017/10/03/the-worst-weather-conditions-in-penn-state-football-history/

[losetoa6turbo]

There sure looks like alot of old peeps in here like me lol. 

Gefs not looking too bad for this timeframe.  Here's h5 leading into ...and slp clustering.  Looking at individual h5 plots there's several members with either a cutoff or energy getting south of the mid Atlantic. 

[losetoa6turbo]

Just looking at Happy hour Euro at 144 to me it looks like sw energy is stronger and ns energy looks to come across to set up confluence closer to the timing our potential storm would be on our doorstep. But who knows . It might be like extrapping  the Nam with the Dgex 😂 Curious to see 0z.

[Penn State]

GFS AI (GraphCast) had a similar track.. though conditions were much warmer. Nothing to supply the cold.. no H to the north. 

[Penn State]

What a complex.. but interesting.. set-up is coming our way. At 00z.. GFS shows little as the GDPS spins up a significant storm. Looks to me it’s all about when the trough goes negative. If northern stream can dig.. the trough can orient far enough west.. and has time to go negative (but not too early lol).. This may have an opportunity. Canadian has some similarities to the AI. Long way to go! 

[Penn State]

The 06z GFS didn't show a big storm.. and it was disorganized.. but you have to like the H to the north. I guess my question is, can that trough go negative sooner, causing it to intensify? With the GFS being on the progressive side, I think that's plausible. Nice to see a consistent storm signal at least.  

[Penn State]

The 00z ECMWF had the same idea.. but was late as well. Once again, a deeper trough, negative.. sooner, I would think helps. 

[Penn State]

EPS and GEFS Members seem to have gained a little clarity as well.. definitely more defined than yesterday. 

00z EPS (192-240)

06z GEFS (186-234)