SnowGoose69

Yeah, exactly why 12/25-12/31 may be where everyone from DCA-BOS sees a snow event if this fails...the PNA does not go positive with a ridge on or just inland of the W Coast until then...the ridge positioning through the next 7 days has screwed us with cutters or inside runners before.

We easily could see a GFS/Euro total cave tonight and the solution may still be wrong and something totally different may happen...we've seen many occasions where one suite caves at 120-144 and then the end result is grossly different than even that is

UKMET is definitely closer to the CMC if you ask me

I said in the NYC forum that if that idea the GFS shows happens the storm would not track as far west as shown, that lead wave would probably drag the zone SE for sure

Even the CMC is a disaster for the airports...NYC airports getting those FROPA events usually have LIFR vis/cigs, major low-level shear and 16025G45KTs....no matter what it'll suck for the airports, just a question on the roads and the GFS is worse for that

The GFS Op taken as gospel is not realistic...that lead system would probably drag the baroclinic zone east a bit and that low track would not be that far west in the end...we'd also snow alot more from 168-175 than is shown...the systems which track up the coast from SC almost due northward usually result in insane isentropic lift and snow rates before the changeover like a 11/2018 or 1/87

As a whole if you're dealing with some sort of major northern branch difference in the models there has been a tendency the last 5-7 years for the GFS to own the CMC and Euro, especially in the La Nina years. Obviously 15-16 was not but many times the last few winters there has been a northern stream "Argument" amongst the big 3 models at D5-7 and the GFS has seemingly won that argument most of the time due to the La Nina state IMO

The ICON basically went full mid January 1996....that exact sequence occurred like 3 times in a 12 day span

Recent years when in a La Nina the GFS has tended to be better with these big events as well as the CMC....the GFS likely because it is much better with northern stream dynamics as a whole and those can control the show in a La Nina. As we get inside 6 days if the GFS is showing a better dig/better WRN ridge than the Euro/CMC I would like where we stand whereas if it begins too shallow of a dig with the northern shortwave we probably are in trouble. One thing I do not think happens with this event is the northern stream destroying it and resulting in a FROPA. We have a bit too much of a Nino like thing going on this season so far with the southern stream

All models do. If you look at MOS numbers in a situation where you're going from rain to snow you'll see it showing numbers like 40/40 39/36 38/32 38/30 37/29 hour by hour for temp, dewpoint when in reality you'll progress 40/40 38/36 34/32 31/31 30/30...as for why they do it I am not sure, you'd think the components entered into models would be able to perceive surface temps dropping due to precipitation...to a degree the LAMP MOS sometimes can resolve it but not well

1/10-1/11/1984, 2/1-2/2/1985 and 1/26-1/27/86 all had that sort of situation unfold.

I actually think the EPS members mostly show a +PNA which is another reason I more or less tossed the Euro Op idea...the idea itself may be possible but probably in a transitory way...no way would the trof set up shop like that even with a neutral EPO and PNA

2000 and 2010 were both a missed phase away from being nearly snowless...89 was snowless more or less...it shows how tough it is in December even with a decent pattern to get a big event here near the coast

Was always possible we would maybe get a SWFE type event before the PNA went positive but the tendency so far this season early has been for more phasing and or stronger systems so I wasn’t quite too in love with the period before 12/20

During La Nina winters in the absence of blocking if you're talking about a phasing system which involves major northern stream involvement the GFS has a tendency to be better. But in this case with the strong -NAO and us dealing more with an existing system undergoing a redevelopment there is a much better chance the other models are likely correct.

It might be coming at 240 on the GFS

You won't get many of those in a La Nina

Really comes down to how far north the system can initially get...anything from a track too close, perfect, or even a miss is possible at this stage.

Meanwhile the GEPS really looks more like a positive PNA ridge than the GEFS EPO ridge

Those patterns so much depend upon the orientation of the block. The 12Z GEFS has it oriented on a positive tilt into NT and BC but in 4 days if the models orient it more over AK you obviously have a huge SE ridge. It’s hard to get that 93-94 -EPO

It’s going towards the EPO block look for sure but we’ll need the AO to stay negative or eventually the SER pops and the cutter threat comes back probably

It’s still a tad too much SE ridge post day 10, whether that’s a long term thing or just a brief 5-7 day shift while the pattern goes more -EPO remains to be seen

Ideally we want the GFS to be less ridgey in the southeast after day 10, especially south of SNE

you’d have to think if we go into a cold AMO soon that’ll change eventually

We had several stretches of warm with a -NAO or AO in the 80s and 90s. It may just not have been as pronounced as recently. I know 85-86 98-99 99-00 01-02 all had stretches of a couple of weeks where the NAO or AO were negative but the PAC was terrible and we were warm. Most of the time though it was a GOA vortex that did us in back then vs a very strong -PNA