ORH_wxman

Many times, SWFEs were at some point cutters on the models and then they trended colder. That is one reason you don't want to freak out every time you see a cutter out in la-la land on the models....esp if there is some cold hanging around to our north.

SouthWest Flow Event. That is describing the flow aloft, not at the surface. Typically those systems where it might snow on the front end as a storm trying to cut to the west hits a strong high to the north....we'll frequently flip to sleet and ZR and maybe even rain in those too, but you never really torch in the warm sector because the storm tries to redevelop and track over the Cape. So you might get this type of progression for weather: 1. Snow on the front end...temp in the 20s (maybe 2-5" of accumulation) 2. flipping to sleet, temps still in the 20s but creeping up to near 30F 3. flips to freezing rain for a few hours as temps continue to clibm near freezing 4. Temp finally inches above 32F and you get cold 33-37F rain for a bit before dryslotting.....then temps eventually cool back below freezing behind the storm. Some SWFEs are colder than others...and sometime we can stay mostly or all snow. But the above is probably the most classic representation of how the weather plays out in SNE during them.

There's always been a few ensemble members toying with the idea too....again, low probability initially (but now increasing quite a bit), but when you consistently have like 10% of the members showing something at 6+ days out, then you should at least consider it as a real possibility even if you wouldn't actually forecast it on your 7 day outlook.

Late next week is the 12/15-16 system....if that tracks to our west, then it will wipe out any pack from 12/12.....but there's a chance we end up with more of a SWFE and in that case, any pack would probably survive at least in the interior. But lets see what happens for 12/11-12/12 first. That system is going to affect the one behind it. We need a pack to protect first.

It looks colder behind the 12/15-16 system....doesn't look downright frigid at the moment, but a generally seasonably cold pattern. When the EPO ridge spikes like that though, there's always a chance we get an arctic shot, even if it's temporary. But right now, my money would be on a bit below normal temps when you have a split flow -PNA/-EPO/weak -NAO.

That big ocean storm you see way out to the east is the 12/11-12/12 system. So clearly that system will have an impact on what happens 12/15.

You can see it on the individual ensemble map....there's a cluster of redevelopers

Yes and we want it north since it gets squeezed ESE pretty quickly.

Def getting closer but most are still a miss. Keep it trending though.

Yeah, the NAO blocks are most useful when the PAC is bad. IF 12/12 and 12/15 work out, it will be because of the NAO....the bad PAC would otherwise send both systems into James Bay....and 12/15 still might do that, we'll see. The LR looks nice because even though the steroid block is gone, the NAO is still negative. Lots of weakness up there, which helps out some...esp with a more favorable PAC. I don't think we're going to get a +PNA though like some were hoping...at least not prior to Xmas IMHO. It looks to me like still a -PNA but it is split flow with the -EPO....that, combined with a weak -NAO, is pretty nice. You don' have this massively phased trough out west due to split flow....so even if troughs dig into southern CA, you still have the northern stream coming down from NW Canada/AK and then the weak -NAO keeping heights in check over far SE Canada.

2-3 days is plenty of time between storms. It would be more unusual if it was under 36 hours between them.

EPS has a lot more members that are snowy for 12/14-15 than 12z fwiw…but it’s pretty clear that the 12/12 evolution is going to affect that storm. A deeper 12/12 system seems to help suppress 12/14-15 more.

Trend overnight for 12/12 was pretty strong….cross-guidance sig on that. I’d like to see another one at 12z today though before taking it a bit more seriously. There’s def some potential there though. Due to the blocked flow, something forming and sliding to our south could be somewhat slow moving.

Yeah I mentioned that to Scott earlier on how the GEFS looks finally good out west and it’s not way out in total clown range anymore. It’s inside of 10 days now on the clear improvement. First time we’ve had decent agreement and also having it get closer inside of d10. I also am not sure why everyone seems to be Writing off the threats next week. Except Tip….I know they are fairly low probability but they aren’t total lottery odds. There’s a chance we get something out of either. I think the expectations got so built up when the models were showing insane look at the end of November.

It's a very good pattern, the color shades are just showing the change between 00z and 12z....they aren't height anomalies. The 00z EPS was kind of ridiculous so I'm not surprised it tamed down a bit in the long range. More importantly, the 12z GEFS has a significantly better PAC by D10 and it continues to the end of the run, so we're getting some agreement now which we didn't have previously.

Just catching up on post-Euro....seems like the PAC improvement is now inside of 10 days on all ensemble guidance...so even if we strike out in the next week or so, it looks like we'll have a good situation to work with beyond mid-month.

Ukie has the shortwave but it gets sheared out....it does produce some onshore flow and SN- for like 40 hours though, lol.

You ran that run from your basement tho

It’s not a high probability but we def can’t discount a meaningful system for 12/11-12/12.

Block evolution on the the two mdoels is so different. What a nightmare.

Just saw another frame. That would be quite a bit better than Dec ‘96 system #1. Esp for coast. I think you had about 3-5” of paste from that one? This run would easily give you warning snows.

What a little nuke. That would crush the interior. Coast even flips. Kind of reminds me of the first Dec ‘96 system.

GEM is actually going for the system on 12/11. A day earlier.

Amazing how different GFS and GGEM are at just day 4. GEM is def going to hit us on 12/12 again this run. GFS does have a system for 12/12 but it’s way south. Not really a good upper air shortwave with it like the GEM. But the differences are already huge on these runs by even day 3/4.

I wouldn't sleep on 12/12 yet either. Low probability but hard to trust guidance when there's a lot of stuff that has to happen first and there's a good chance guidance doesn't deal with all of the Dec 9-11 stuff downstream accurately until we are closer.