Bob Chill

GEFS continues to look very cold during the first week of Dec. -EPO driven patterns are volatile with temps so the smoothed mean can be deceiving in that it shows cold to very cold temps for the first 7 days of Dec. If the GEFS is right in transitioning to a -EPO driven progressive pattern the ground truth will be a series of fronts and big temp swings and not 7-10 straight days of cold weather. While the pattern isn't perfect or one that makes me think easy snow, the fact that Dec looks to start off with some sig cold shots is very encouraging. Haven't had a Dec kick off with legit cold around since 2013.

Taking current d10+ ens guidance verbatim, looks like we play with some fire. Epo ridge is a bit too west and there's no coupled +pna so that implies some very cold air dumps right down into the rockies before bleeding east. There will be a battleground between airmasses. It's entirely possible the mjo is influencing the pna. Could be any # of things really. -PNA periods in late fall are as normal as the redskins having losing seasons.

If we lose the -ao/nao and get a massive epo ridge going like we're seeing it changes the way we can get snow. It's a tradeoff because we basically need sig temp help in early Dec. Especially I95 eastward. The big epo can def deliver big cold and it's looking more likely as we move towards Dec. The bad part of the pattern is cold highs will be on the move and luck/timing becomes more important. Rain, flawed, and mixed events are the most common during -epo/+nao patterns and they can be very frustrating with cold running away before precip. I'll only get worried if a shutout pattern shows up. Right now all signs point to early Dec not being hostile. Can't ask for much more than that.

My biggest question is whether or not the models are rushing or flat wrong about the ao/nao going positive in 2 weeks or less. The nao block coming up was totally missed from long range.

One thing that can be very misleading about ind ens member output is the resolution is lower than the op and if you loop the members that produce, some always do it in a way that's pretty much not possible irl. I agree about clusters though. Get a nice group of similar solutions and outcomes and it increases confidence in the opportunity. Conversely, if there are a few giant hits embedded in an otherwise crappy run the snow mean can be very misleading. One thing we can all agree on is ens member snow output is massively biased to the upside and is a very unreliable way to assess our chances.

Not that I think the GFS has discrete features modeled accurately d10-11 but the run is a great example on how we can still score with a -PNA. It's all about the NAO and 50/50. If the NAO is real then it could provide an extended window.

Check out the h5 loops on the 18z gfs & gefs and stare at Greenland. Starts in 4 days and never lets up through the end of the run

18z gefs is loaded with members showing height patterns that make me think snowstorms are possible in early Dec. Looks like an active pattern with plenty of cold near or overhead. STJ would be juiced on most of these solutions too

Yea, we seem to be getting played similar to last year except this time it's breaking in our favor. Cfs weeklies have been a total dog turd lately. Here's week 2 from a week ago: A week later week 1 looks like this: Completely missed the -nao from just 2 weeks out. Lol. Anyone who worries about the crappy look on the cfs for weeks 3+ needs to look at these panels and ignore weekly/seasonal guidance. My skepticism of Dec being good is slowly becoming confidence that we kick off met winter tracking threats in the med term.

Yep, the whole atmosphere is full of good and bad features upstream and down. Normally a tendency for a -pna is a dagger in our area with one exception... add in a -nao.

I'm excited about the med term and what it implies down the line... in just 4-5 days we should have the strongest -nao we've seen early during season since 2010. Complete agreement the upper level ridge closes off and parks for a while.

Yea man, I keep liking the entry into Dec more and more. The big epo ridge makes complete sense and is what I've been expecting to roll forward. The nao is even more interesting because it's in the med range and all models agree on it. These types of features can be stubborn and models don't do well with figuring out when it's going to relax. My gut says the neg nao will likely be stubborn and it's happening at a perfect time. We need extra help through most of Dec. Get the ao,nao, and epo working in our favor and it's actually not that hard to get an event out of it. I'm expecting the eps to cave to the gefs with the nao. We'll have a stout neg nao in just 4-5 days...

The numerical calc is 1000mb pressure but we all know what a good h5 look is no matter the numerical index. These type of long range op looks keep happening and it's intriguing. Not that I think the gfs is right or anything but seeing these solutions are a potential clue that an extreme blocking event is possible

This is just for the eye candy aspect ofnthe panel. I don't need a reminder that it's d15+ on an op run. This is one way to turn a trough in the west to a big storm pattern. Lol

I totally agree and it could have sig implications down the line as climo gets better. As we start moving though Dec normal temp regimes can work here. A stable -ao/nao can overcome other flaws like a so-so Npac. Last year's pac base state was too much to overcome for most of winter but we had literally no help from above.

Simplistic view would be to just watch the EPO/PNA. We're going to be fighting those teleconections for at least a week it seems. Probably longer. However, ens are certainly hinting towards a -EPO reload and the PNA trough rolling forward. If that does in fact happen then our first legit "snow window" should present itself sometime during the first 10 days of Dec. OTOH- if we keep getting teased with a +PNA/-EPO in the long range only to have a hostile pattern dominate then it could spell trouble for at least a portion of Dec even if we do have some help in the AO/NAO domains. As I've said multiple times... I have mixed feelings about Dec as a whole. Kicking the month off with a window where it can snow would be our first win. If the AO/NAO continue to cooperate into late Dec then it's possible to overcome a sh!tty Pac. That's way too far down the line to speculate on. Let's finish shoveling our early Dec storm before freaking out about the rest of the month.

Lol. Yea, it's tenuous depending on which way it breaks... My gut instinct is telling me that the -pna rolls forward and a -epo ridge builds. Retro the weeklies pattern and we're toast. Literally.... Eta: no sign of a se ridge popping and that's always a good thing.

As the days go by the less we know about Dec. Lol. I'm not mad at the weekly plot you posted. It's not that far from something that can work. Better than last year's no chance in hell pattern

All major teleconnections can be stable or volatile. I'd say the PNA and EPO are similar in their inherent stability/volatility. Sometimes one phase dominates for weeks/months and other times it bounces back and forth. Right now is a transition month so there's too much inherent volatility to predict anything beyond 1-2 weeks. It's entirely possible that the PNA spends more time - than + during met winter. Seeing a -PNA during late fall or early winter is very common and imo isn't a much of a clue for long lead guessing.

Yep. Looks like a typical -PNA period where the western ski areas get dumped on for a couple weeks. Not warm here but still far from a good snow pattern here. However, the PNA typically oscillates so even if the EPS is right it's not unreasonable to expect the PNA to flip back + after the storm cycle. These types of patterns commonly hold for 1-2 weeks. We're still a month away from our climo not fighting us with every little detail. I'm good with everything as is and can easily envision how it could improve at a time when our area stands a chance at a snow event.

I'm surprised how positive the ao and nao are. Ignoring everything else it's never a good sign and not one I want to see in Dec as it can be a bad omen if it were to happen. Maybe it's the opposite of last year and weeklies/seasonals keep showing a flip to +ao/nao that never verifies.

I've been too lazy to sign back up with wxbell. Someone needs to post weeks 3-4 from the euro weeklies unless they look like turds. I'm ignoring all bad looks until further notice

I just look at the areas with the strongest height anomalies as those features are what the model suite is seeing as the highest probability. Lowest heights north of the Aleutians and in the NAO region and strong ridging north of HI is a really bad combo for snow in the eastern half of the conus. The CFS implies a warm conus pattern with a storm track to our west. If the cfs weekly or monthly pattern is right then the hottest thread in our sub will be the panic room. Lol The good thing is seasonal guidance totally missed the Nov pattern. Especially the AO/NAO region. Another reminder that long lead models are unreliable and cannot be trusted. I love what I see right now in real time through the next 10 days. Gets even better d10-15. If that becomes a persistant pattern then the panic room might go out of business.

GEPS jumping on board too and throws a -NAO in just for fun. GEPS has a really nice mean pattern. Cold supply, -EPO/NAO combo, split flow/bagginess in the SW undercutting the PNA ridge, and a 50/50... I mean what's not to like on this panel other than the fact it's the GEPS? lol I had a hunch the EPO would play nice at times this winter. Not claiming I thought it would happen out of the gate but nice to see the general idea may show up pretty quick. \ I'm waiting for the CFS weekly to start to cave on week 3 but it's steadfast showing a dog doo pattern in early Dec. I put a lot more credence in the global ens than seasonal stuff but considering we're still talking 2 weeks out it's hard to hug any outcome yet.

-EPO signal keeps getting stronger on the GEFS as we close out the month. Something to watch for sure. It's one way to defeat climo temps that normally make it hard to snow early season. A lot of members have either sig cold in place or nearby as we enter Dec