December 2025 OBS and Discussion

[MJO812]

1 hour ago, SnoSki14 said:

You aren't getting snow in the city next week. High is retreating, low will cut west. Not enough cold out ahead of it either. 

It's a lost cause

Quite possible but its still close to watch it. 

[eduggs]

The surface features aren't driving this outcome. The position and strength of the surface highs and lows follow the upper levels.

The trend over the past 2 days is for the shortwave to not "dig" as far south. The vortmax that passes through the Great Lakes is becoming increasingly prominent. The path of this shortwave and vorticity advection ends up tracking pretty similarly to Sunday's wave that precedes it. That leads to a stronger surface reflection (primary) near Western PA and southeasterly low level flow that quickly changes snow to rain along the coastal plain.

The hope is that maybe guidance is keying on the wrong packet of vorticity and that the models will shift back towards a more favorable trof evolution. As of now this is transitioning towards a SWFE-type event that favors the interior, particularly New England. But it's still close to a wintry outcome... and highly trackable.

[eduggs]

It's difficult to know how significant it is that the GFS op is significantly wetter and further west compared to the GEFS mean. The GEPS and EPS are also a bit southeast and drier. Obviously the averaging-effect decreases the mean precipitation the more you go out in forecast time. But the majority of the individual ensemble members are also well east of the GFS. The op also appears to be a bit faster than ensemble consensus... maybe in response to the sharp Great Lakes shortwave/vortmax that is at the leading edge of the trof.

I suspect the op (maybe higher resolution?) is more accurately resolving the shortwave progression than the ensembles. I expect the ensembles to play catchup, and I don't think we're done trending yet.

[eduggs]

Just noticed that there are still pretty big differences between the CMC and GFS days 4-5 at 500mb. The CMC actually doesn't look too bad aloft... that's a borderline snowstorm to pretty close N&W. The GFS upper levels look like they would support more rain and less snow than depicted. I feel like the GFS will end up more right... hope I'm wrong.

[eduggs]

The 0z UKMET and 18Z ECM-AI squash the shortwave and yield very little precip. At 4.5 days out this possibility is still plausible.

[Snowlover11]

Nothing burger unless you live 45+ Miles NW of nyc.

[MJO812]

1 minute ago, Snowlover11 said:

Nothing burger unless you live 45+ Miles NW of nyc.

Yep

Typical

[SnoSki14]

46 minutes ago, MJO812 said:

Yep

Typical

This set-up would probably work in January with a colder antecedent air mass. Track isn't bad. Fast flow doesn't allow low to amp up and move inland.