psuhoffman

@WxUSAF this is about as big a “real” ridge signature as I think you will ever see on a day 16 prog. Even a hint of a 50/50 sig.

@CAPE the new gefs is perfect Imo. This is exactly where we want that N PAC trough. This pumps heights into western N America and gets the ridge axis along the west coast. That’s even too far west without blocking but with a -NAO that promotes the broad trough look under the block we want. Pull that Pac trough any further west though and the ridge pulls back into the PAC and that broad trough will split with the cold dumping into the west and a SE ridge will pop. Give me exactly what the GEFS is showing now. It’s not being pushed back in time so far either. Today actually sped up the progression by about a day.

He isn’t wrong for the mid Atlantic though. I’ve run similar studies of our big snow events down here and our best big snow look often has a trough in the N PAC along with a west based NAO block. It’s a big if, but if we do develop a west based NAO block the pac is just fine. Otherwise it’s crap.

Long range gefs is seeing a bit more of a 50/50 signature. That’s one way this could flip colder fast. Get enough of that and it will fight the eastern ridge.

I guess 2020 didn’t end all bad

This is just for fun but the end of the GFS run is how I see our best chance of getting snow. Something like this. It retrogrades the blocking into Canada. Same PAC look with the WPO EPO vortex sensing systems into the west. Which leads to this... that system is trying to cut...but it’s not going too. Look at all the confluence to our north. There is a 50/50 stuck just off the screen and there are lobes rotating around, one is just over top us. The 850s look iffy at a glance but look at all the dry air And as the system approaches the 850s are already crashing in TN and GA when the precip hits the dry air. All that +1 air over NC will end up below 0 once it saturates and has to advent north before we would go to rain. This was an incoming snow event. It may have been a snow to ice to rain event...but it was at least a decent frozen event oncoming. Same crap pac. Being offset by the blocking. That’s what history says should happen in that pattern.

I actually have thought for a while that storm is likely to trend more amplified...but I also think think it ends up mostly a rainstorm so I haven’t given it much thought.

Maybe not but a central pac ridge pattern won’t be any better.

Sorry...I took a lot of heat for that post (@Mersky)and I totally understand why...but it was 100% accurate. I guess I’m not a stick your head in the sand kinda guy.

We don’t have a west based block now. The attempt at that this week failed. The storms that were supposed to assist to retrograde the WAR ended to cutting so far west the instead ended up pressing the ridge east more. The one time in December the AO really ranked we did get cold enough and a legit snow threat. Details didn’t work out but I’ll take that over playing with the fire if that WPO vortex vacates. Given where the tropical pac forcing is...if we lose that n pac vortex I don’t think we get the PNA everyone wants. My guess is we pop a central pac ridge western trough.

I’m of the mind it doesn’t need to improve if we get a west based block. Actually is the N PAC trough vacates and we get a ridge there that’s a worse look with a -NAO.

Now you’re getting really specific but yes ideal pna ridge axis is around Idaho

I think there is some confusion with what an EPO is. An extremely east based EPO coupled with a PNA ridge centered along the western US into western Canada is a great thing. But that’s not a typical EPO and I doubt that’s in the cards. A typical EPO ridge extending from the central PAC into AK is too far west and dumps the cold into the western US. Those both fall into “EPO” but for our purposes are totally different patterns. One good one bad...both under one index.

@CAPE everyone is mad at that north Pac trough but we’ve had some epic snowfall regimes with that look. 1996, 2003, 2010. And that trough is keeping the central pac ridge suppressed. That ridge (remember my soul crushing post last December)is the single biggest snow hope destroyer there is. It can even destroy a -NAO! We have occasionally overcome a pac ridge with a -NAO like feb 2006 but it was still a warm month and if they one storm hadn’t worked out we would have wasted a beautiful block because of that pac ridge. My number one “want” is keep that central pac ridge away. This look on the long range GEFS is getting dangerous. Retrograde that WPO vortex anymore and that pac ridge is going to go ape and we will be fighting a SE ridge even with a block! A perfect pac isn’t in the cards. Getting some huge stable PNA ridge just is unlikely with the current forcing. So imo a WPO vortex is by far the lesser of 2 evils v a central pac EPO ridge that dumps cold into the west while we ridge out! I don’t care about cold it it’s on the other side of the country!!!

Maybe. But sometimes with a -NAO a EPO ridge dumps the cold into the west unless it’s an east based EpO that extremes into Canada. If it’s a central pac EPO ridge into AK that’s actually a bad sign. It’s one of the few NAO killers.

Lol that’s super rare. Typically a ridge into AK and you get a trough dumped further west then that. Most of the time to get that wavelength spacing to work requires a -NAO also.

Yea I think we’re making slightly different points. I’m saying I hope that isn’t true because of an EPO is the best way to get snow in the new normal...the new normal is going to suck.

The EPO was positive in most yes and in the others it was neutral or only weakly negative. It wasn’t driving the bus. An epo ridge usually promotes a trough too far west for us. And a full latitude PNA/extremely east based EPO ridge absent a block is a cold dry look. Once in a while you can get a crazy storm like March 93 from that kind of ridiculous full hemisphere wave but I’ve shown in the past (when someone was throwing around that analog) how that was a huge anomaly and most of the time with a similar look we just get a short arctic blast then warm up. An exception would be what we had in 2014, an extremely positively tilted east EPO ridge that poked all the way into the AO domain. Then we can suppress the SE ridge and get progressive waves. 2015 worked because the TPV got displaced into Quebec. That works too. But those are really rare anomalies that I can’t find that many examples of historically. My point is the EPO alone doesn’t work. We need other factors. And yes an epo ridge with a -NAO can work...but actually a +EPO -NAO correlates to snow even more so obviously the EPO want the determinant. You’re point about 1-3” snows could be valid. I’ve not done much study on that. That’s not really my thing.

On the surface. But overall they aren’t as different as it seems. It’s a critical tipping point where there is enough space to amplify and get precip from that SW pass. GFS and Euro are barely on either side of that threshold. A minor shift in the mid and upper levels by either flips it’s surface solution.

Since 2015 I’ve had 9 warning level snowfalls. Not a single one was EPO driven (and we’ve had several beautiful epo ridges in that period). 7 were AO/NAO driven and 2 were PNA driven. Historically the numbers are similar. The EPO has never had much correlation to our snowfall. 2014-15 was an anomaly.

I don’t disagree but that’s not a trade I want to make. Im a snow fan not a cold fan. And a -epo will never be as effective at promoting a favorable storm track for snow. I think 2014 and 2015 gave a false impression of what a typical epo ridge pattern is. We’ve had quite a few great EPO ridge patterns since and none produced that result. This example from 2018 is way more indicative of a “normal” result in an epo ridge pattern. A lot of rain with a lot of snow to our northwest. I could pull out several more epo ridge patterns from the last 5 years that produced some cold into the US but no snow for us. ETA: you actually can do “better” in a EPO driven pattern then the typically more favored parts of our region, sometimes getting clipped by late developing progressive waves or follow up systems. So for the eastern shore maybe it’s not as bad a trade lol.

@CAPE but technically the long range guidance is starting to “hint” at a workable temp profile. This is the end of the GEFS. This should support what we need.

It’s all symbiotic. The way you knock that down is to get storms into that area. The wave break from those amplifying storms helps retrograde the ridge into the NAO domain. What derailed the last attempt to set off that chain reaction was the boundary ended to so far NW that storms cut and got stuck up in Canada. Never making it into the regions we need to set off the positive feedback cycle.

I was comparing them to the projected looks in mid January. Looks close enough to me. GEFS and EPS extended What I was talking about was the fact people are saying even that look is no good and why it’s still warm on the long range guidance. Now if that look never comes this is moot. But that look is actually a great snow look historically. That’s all I’m saying. Your second point is interesting. The one biggest change is the enhanced pac jet. But that seems to be a new normal since it’s existed for quite a while now regardless of enso state. But perhaps that has made that look less supportive then it once was. And your point about outdated analogs is true. But that also kind of feeds my point which summed up is “we better hope that look still works because it’s responsible for A LOT of our best snowstorms and it’s not like we’re picking up new ways to snow to replace it in this warmer climate base state”.