Potent Thanksgiving Eve Storm Could Bring Travel Headaches

There is the potential for a major east coast storm to bring a lot of havoc to people in the eastern CONUS during the busiest travels days of the year. Some areas could even see a white Thanksgiving, imagine that. There is still a lot of uncertainty however in the exact track and intensity of the system. In this blog I'll take a look at the pattern this storm is working with and check out the latest from the GFS and EURO models.

The system in the southwest U.S. is the main player that could bring this storm together. It is an upper level low feature that is being fed energy from the eastern Pacific Ocean, indicative warmer than normal SST's (sea surface temps.) and an active STJ (sub tropical jet stream). The other essential piece to this storm is not shown on this map, but it is out northern stream energy which could potentially phase, or join up, with this upper level low and produce a massive storm right before Thanksgiving. 

Here is where the 2 major global models stand:

GFS- out to sea, minimal impacts

EURO- large, powerful, inland track storm with snow for interior areas and elevations / heavy rains & wind along the coast 

By looking at the upper level maps, we can see why these models differ

Above is the GFS 500 mb vorticity map, which shows why this model is taking the storm out to sea. The northern stream energy is ejecting too quickly out of the northern U.S. while the southern stream energy remains a separate entity in the southeastern U.S. There is no phase and ultimately no storm to worry about. 

The EURO on the other hand amplifies the ridge in the west (+PNA) which allows the northern stream energy to slow down a bit, dig into the trough, and phase (at least partially) with the southern stream vort. The end result is an impressive storm along the coast bringing heavy snows into parts of western/central PA, central NY, and New England. 

GFS accumulated precipitation maps obviously show nothing, besides coastal areas, since it takes the storm out to sea due to the progressive nature of the way it is handling this storm with the upper level energies. 

EURO on the other hand is extremely amp'd up due to the reasons I explained above and is showing 2-3 inches of rain from DC to Boston and significant snow for interior sections of the northeast. 

Here is the EURO snowfall map by mid-day on Thanksgiving Day. 

My Thought's

1. The GFS Ensembles are well west of where the operational is and some individual members show a EURO-like solution. There has also been evidence of the GFS suffering from convective feedback issues. 

2. A week or two ago we were also tracking a possible coastal storm that never came to fruition, even though the EURO was bullish in tracking a storm up the coast. The GFS won with the out to sea solution. The pattern then called for the out to sea track. The pattern now still seems suspect to me that supports what the EURO is showing. 

3. Our NAO is still positive, but the difference with this system is the EPO is negative and the PNA is positive. This boils down to timing of the northern and southern stream energies. The GFS has a bias of being too progressive in northern latitudes of the CONUS with regards to the northern energy, but the EURO also has a bias with the southern latitude energies of the CONUS. 

4. At this point, I favor a track between what the GFS and EURO are showing, with a not-so amp'd up system like the EURO shows. I think a sub 1000 mb storm is realistic right on or off the coast of NJ, but it should be a quick-mover with the lack of blocking. Originally I favored a completely out to sea track, but I think that is looking less likely at the moment. I definitely do not favor the interior bomb the EURO is currently outputting. 

5. It is still fairly early and I will have another update with an impacts map out by Monday. The map will include potential rain / snow amounts. We are looking at a time table between late Tuesday night into all of Wednesday. Thanksgiving Day itself should be dry, with gradual clearing throughout the day. It will be cold though. Just keep in mind the worst case scenario, which is the EURO model, if you are traveling. Heavy rain, high winds, snow, you name it; it is there to worry about.