Bob Chill

Yes, each run is initialized with brand new data then model physics takes it from there.

BWI: 22.3 DCA: 14.1 IAD: 25.7 RIC: 13.3 TB (SBY): 11.5

Hoco/Moco death band is evident on this panel.

They pretty much work in unison right? HP can only move where the 50/50 lets it. The handoff is uber complicated and we're going to get teased bigly every 6 hours. The front running WAA piece isn't nearly as complicated and also (stating obvious) the most likely way we'll get snow in the DC area. You are in a much better place for the big show. I've seen this show too many times and even when models are straight locked and loaded with 1-2 day leads the script is re-written in real time and my yard is kicked off the stage.

I circled the most important change on the GFS. There's defined separation with the trough north of the closed ULL. The cuts off the destructive mid level return flow that will easily wreck the column overhead and north of us. Since the features are separated it allows the dynamics of the ULL to stay consolidated and draw in colder air and not allow a big warm mid-level push. Is it believable? I suppose it's possible or the model wouldn't show it. Give me like 5 runs in a row with separation like this and my inner weenie will do things. ETA: I didn't explain things properly above... The separation is what allows the track to be further south (no tug poleward) as the closed low crosses the region. Keeping the dynamic core of the ULL intact allows good things to happen this far south. I hope that makes more sense. I'm having problems with thoughts and words... lol

Hard not to stare at this...

Dude it's the ultimate mid range tease... lol. Is the entire progression really going to be lateral like that? It's possible but I'm not placing any bets. I do like the closed ULL track. Even without CCB stuff we're on the good side of dynamics/instability as the ULL exits stage right. This whole thing should keep me occupied while my sister drives me nutz in CT over the holiday.

Agree @frd There's a big difference between a sudden spike to +2 or 3 or whatever and a quick relax versus a flip to a giant rotating blue ball parked for weeks/months. Too early to decide which way the current move is going to go but every day that goes by gives me confidence that we're not quickly flipping to long term doom and despair. @psuhoffman Ens are at odds down the line but the trough near HI keeps showing up so a +pna seems very logical sometime after the AO flips positive. Keeps things interesting. I am expecting a warm stretch before the pna goes up. EPS may be too fast in bringing a trough back in the east. Sig spread between eps/gefs/geps D10+. ETA: imho- the biggest risk for an extended crap period (like 1-2 weeks) is a trough setting up in the GOA. There's a cluster of gefs members hell bent on that happening. I'd like to think the pna saves NA from a pac air flood but the underlying risk is def there.

Yea, I want to believe there's a way we can get into some coastal action but there's too much to overcome without significant changes. 18z gefs actually shifted north with ind member slp in the midwest/OH valley. This plot is not a way we get coastals. The lows to the SE have no energy to work with. The track of the primary would pull a lot of warm air to the mid levels overhead.

Unfortunately the track of the upper level low is too far north the entire time. Even though you see a surface low pop right off the coast, all the best dynamics and lift are well north of us. Any phasing will take place north as well so the slp won't blow up with a CCB/deform anywhere near us. Is there a way we can get into legit coastal action? Yes, there is but not unless the upper level low tracks 150-200 miles south through at least southern VA (NC would be better). We have 3 days or so before models will lock into the track of the upper level low so a south trend better start at 0z tonight. Lol I can envision 2 realistic ways we can get measurable snow. If the front running band of waa precip juices up and our column stays good we could get anywhere from an inch to maybe 4-5 inches if the stars align. The second way would be the upper level low to track far enough south so we get dynamically driven instability snow as the upper low passes under us. Wouldn't be a big event but someone could get under a band and get some heavy snowfall for a time. Imho- I don't see any way we can get a legit coastal storm unless there are major changes with the track of the upper low and even then we're playing with fire as these progressions often (even with a good track) love to skip over us.

I think it was a month or so ago when I posted about the PDO potentially shifting towards the positive phase if the pattern of troughs in the NE pac verifies. It wasn't as much of a shift as I had hoped but the PDO did move positive. I haven't checked the numerical index yet but visually it's no doubt better than a month ago. If the trend holds up for another month we'll have a legit +PDO and that's always a good thing. We'll see how it goes as Isotherm specifically included a -PDO as part of his winter forecast and one of the reasons he went warm in the east. It was one of the few things I saw potential problems with when I first read his forecast.

Euro/EPS both agree on speeding up the ULL next week and that's prob the main reason the op had waa snow working out. There will be a half decent airmass in front on the ULL and the 50/50 is going to try pretty hard to not allow it to run east out to sea. To get "easy snow" just root for the fastest track possible of the waa shield. The "complicated snow" with the ULL isn't nearly as clear cut. Calendar and gut instinct tell me that we're chasing a phantom with the WAA snow let alone an ULL tracking SE across our area but I can't remember the last time I've seen such a beast of a 50/50. Maybe being uber conservative isn't warranted. At the very least... we are still in the game for something. An inch or 2 of snow during the first week of Dec would calm a few weenies down (like me in particular).

I can't think of a memorable cold December since 2010 unless I'm missing something. Climo facts say we will almost always have a warm stretch in Dec. I have no say in the matter but my vote goes for having it happen during the first half of the month as long as winter wx is only 1-2 steps away and not an entire regime change. lol

Looks familiar... kinda like the base state in 13-14. lol. -EPO/+AO/WAR showing up. If that's as "bad" as it gets then at least we're not in a shutout pattern. Checking through the GEFS it seems like there's 2 camps down the line. One camp has a GOA trough, +AO, pac air regime and the other camp keeps things more amplified with a +PNA/-EPO/trough in the east. All members agree on progressive flow down the line. My total WAG is we end up seeing both camps. As the AO goes positive we'll have a period of zonal pac air mild followed by the PNA ridge going up and trough returning to the east. I'm totally good with a mild/crap period as long as it's short and morphs into something that can at least keep us in the game. GEFS/EPS are both trending away from epic disaster.

It's all about ridging above the closed ULL and the spacing with the 50/50. It's certainly possible for a further south track but even as is the track is defying the atmosphere. Closed ULLs that track over Des Moines rarely work out here and the typical trend is north for these features as leads shorten. This is d5 so plenty can change. Just root for the bowling ball to be weaker and further south through the midwest. Faster would be better too. It's an interesting setup for sure and I'm def watching it. I just don't like the odds here. The ULL is very strong in the midwest and it's going to try it's hardest to push against ridging and confluence. I remember the Feb 2015 storm (superbowl weekend?) that models all had a good track in the med range but guidance kept ticking north as leads shortened and it ended up being a whiff. IIRC, that ULL tracked right over Indianapolis. This one is further north as is. But there's also a blocking ridge to the north and pretty strong confluence to the east. The faster the ull tracks across the conus the better.

Yea, it's a pretty powerful ULL as it crosses the region but taking an unusual course SE as it moves from OH to off the coast. Move the center of this bowling ball 150-200 mi south somewhere around ROA and the best dynamics/instability will cross by in a pretty sweet spot. Convective style snow from a closed ULL is one of my personal faves. Big omegas = big dendrites = high ratio pounding = weenie party. Even if short lived.

Sensible wx (more specifically individual threats) has no skill out in time. Where the line of believable vs unbelievable is drawn is up to the individual. If you want to believe a d7+ op with a snow event then do it. Do it enough and you'll stop doing it. lol. However, large scale hemispheric pattern drivers like the pac jet, AO, EPO, and other major drivers can be predicted with some skill way out in time. Sometimes 2 weeks and beyond. Sometimes months at a time. I think it's completely fine (and healthy) to discuss the big picture and what it generally means. I'm sure most agree there. When I post about long range stuff I'm seeing it from only 1 perspective... is it a shutout or not and why. Right now I'm looking for a real threat window to emerge and I'll certainly post about it if/when I see something. Even if it's 2 weeks away. I'll agree that the real disasterous look is backing off but I still don't like the overall big picture for snow chances in these parts on any piece of guidance right now. If the +AO is in fact temporary and things start to shuffle back to something decent then it will happen at a time when it's not extremely hard to snow here. Outside of a flukey flawed lucky event, I don't expect much tracking for a while. The first week of Dec could offer something flukey/flawed but overall it's not a good looking period. Beyond that looks worse. Beyond that is starting to look less worse but not close.

Being totally honest... if we're going to have a shutout pattern then bring on warm and dry. Mountain biking and hiking are good therapy for crap patterns. Unless we see some drastic changes over the next week looks like a warm period is on the way. Hopefully it's just temporary.

This is like the opposite of model porn. I can't recall ever seeing the AO this positive before. Lol

EPS isn't that scary. Trough near HI is a general connection with a +pna. Workable. Ultimately I'd like to see the ao not give up like the redskin's secondary. I've never expected deep winter to lock in early Dec with all cylinders firing and vsst majority of our snow events are flawed. Big ones have common needs but smaller events pop out of nearly all partially flawed patterns. I'm bringing up the AO concerns because that's the king of decent snow events and also a teleconnection that can be modeled fairly well at longer leads.

Exactly. It's not that a +3 or +4 AO over a couple days means we're in trouble. It's when we get a monthly mean AO of +1.25 or higher that spells trouble. The thing I don't like seeing is the size/expanse of BN heights in the AO region. If ens are right, the entire AO domain space has below normal heights. Upper level features like that are hard to break down. Typical strong AO periods take 45-60 to release their grip. I'm not implying that I think ens are a lock and have it all nailed down. Lots can change over 1-2 weeks. However, it is one of the Dec features that's kinda scary and something to not ignore. Similar to a big vortex over AK. Things you never want to see in December...

There's def a window first week of Dec. Might have a couple shots mixed in there. Just pray the +4 AO down the line is a phantom. We'll spend half of met winter trying to get out from under it.

NAO domain is really small and volatile so that doesn't bug me. It's the damn AO turning into a cold vacuum and polar jet magnet that has me concerned. What's being advertised now isn't just a positive AO... it's an extremely positive AO and will no doubt make it really hard for winter wx in these parts if that's where we're going...

Not a fan of the gefs/geps trend. Both agree on a legit +ao/nao and midlatitude flow looking like a pac air flood. Current long lead look is very similar to the crappy seasonal/weekly guidance for Dec now. Could be totally wrong or just a temporary flip before a cold pattern returns. Or it could be the beginning of an extended mild period in the conus.

Gefs is north of the op but def shifted towards favoring some kind of transfer and sig precip event. Personally, I despise these kinds of setups. Too much heartbreak... Could be a forum divider with CAPE on the winning side. I really hope the primary shifts south. I can't recall an event with the primary tracking so far north in the midwest that works out. Philly on the other hand...