jwilson

I think the NAM is still too far out of its comfort range to be instructive. There's the rare occasion where it picks up on something, but usually you want to avoid the NAM until its under 48-60 hours. As you can witness on the NAM, the high pressure is bouncing all around, but I think it should be fairly locked in because of the overhead blocking (-NAO) and a ~50/50 low. The system that will eventually evolve into Wednesday's threat is just now hitting the west coast. The GFS at 12Z remains the most progressive of all the models. That solution creates such strong frontogenesis that you'll have winners under an INTENSE deform band with divergence elsewhere. The 12Z even screws much of Central PA that looked "safe" under other, previous solutions. Basically, you get a very narrow range of top snow depth instead of a widespread event. I'm not inclined to take the GFS at 100% right now. That said, the entire system is clearly vulnerable to disruptions, because it is early in the winter and we don't have a colder airmass established. The warm Atlantic waters are another wild card. It's also not near a true Miller A, which is what we really need to see for Pittsburgh to capitalize on these setups. Widespread overrunning snows. It's more like 75% Miller B and 25% Miller A. Those coastal transfers are tricky to time down. Too late and the mid-Atlantic misses out entirely.

Case in point: the EPS has a 60-80% chance of Pittsburgh metro seeing more than 3" of snow this week and a 30-40% chance of 6" or more with a mean through Friday of 5". Game isn't over.

There's still quite a few ensemble members of the GFS and Euro that swing a good bit of snow back across the entire state. Ridging out west, the digging s/w, or the high pressure can all influence the direction the low(s) move. The Canadian came right back to the same solution it had a couple days ago, however. It will be interesting to see if it remains consistent. It was curious to see the Euro come around to that same solution today while the GFS hints a bit more at it, but keeps the flow too progressive. Maybe the GFS is the new Dr. No. The GFS keeps it active through the period. The Euro looks like it transitions to a real +EPO signal around Christmas (not good). It will be curious to see what ends up winning out if the AO keeps tanking while we have less pacific ridging. Perhaps we get an "artificial" -EPO due to a shifting or splicing of the PV.

The GFS also has Euro support (or is it vice versa?). Should be an interesting week ahead. The 0Z Canadian also had a system in this same timeframe, but the surface low tracked right over Philly. We'll see if the 12Z suite alters any details.

Well, it's been quiet here. Rightfully so, I guess, because there isn't much going on in the interim. Long-term, the signals keep flipping back and forth, but a -NAO appears relatively likely. Perhaps in 48 hours we're back to a NINA look, I don't know, but it has been quite a while since we've seen any kind of true, even transient, -NAO block during the winter months. The last -NAO for December I can find is 2009 (we remember what happened then). From a "winter" perspective, 2010 was it, with negative values quite literally the entire year and into 2011. Columns after the year run from January to December. That was the end of our blocking winters. Since then, the only real blocking has come during the summer or fall months, and all winters have averaged well above positive. "A decade under the influence." This might all be for naught, but I figured since there isn't much going on, I'd try my hand at some analysis for the upcoming period, which looks like it could be surprisingly active. First is the Canadian for next Tuesday. After this weekend, which pretty much all models are visualizing a cutter, we head into next week that really looks more interesting. We see it is holding a rather large, singular piece of energy back into the southwest. This is usually a good sign for a big NE snowstorm. There's ridging along the west coast and, although the flow looks transient ahead, I think this is more a symptom of this s/w digging. This is the GFS at the same time: The GFS is much less organized. It is stringing out some of the same energy all over, while also holding a bigger piece back off the coast. It comes crashing in a few frames later: That's the remaining piece of energy coming into Seattle. Still, it keeps it separate and moves some smaller bits out ahead into the great lakes area. Very northern-stream dominant. At the same time, the Canadian keeps bowling: Now it's a closed-off ULL. Pretty much concentrating all the energy right there near the four corners. The Canadian then digs this all southward into the Gulf, dragging and phasing the northern stream energies into one significant trough. On the GFS, however: The American model keeps the streams separate. It has these two distinctive blocs, but it also has a piece of NS energy holding up in Canada. Basically, instead of how the Canadian crashes all this energy together into a cohesive system, the GFS times them apart and prevents things from ever morphing. It's a strung-out mess. See the final GFS look here: As I just said, the GFS is strung-out and tries to dig some of the energy south, but the northern stream is still keeping other bits of energy off the same conveyer belt. Eventually it does form a Miller A (of sorts) on its own, but because of the separation here, the cold air is also pulled away and the trailing system (seen here digging into TX) has no cold air to work with. What we get is a rain storm. Meanwhile, the Canadian: Puts a nice closed-off bowling ball right over the Jersey shore. Even the Canadian setup is kind of off-kilter - resulting in a double-barrel low of sorts - but it brings a lot of snow into the Mid-Atlantic. It isn't a great look for Pittsburgh because of the confluence, but if shifted just a little to the northwest, Pittsburgh would be in the game for the bigger totals. Meanwhile, this verbatim would jackpot areas around D.C., Philly, and New York, almost 11 years to the day after a very similar system did the same. The remaining question is - which of these models has support? As of the 12Z runs today, it looks like every model is kind of doing its own thing. There isn't a ton of agreement on the evolution of these pieces of energy. To be expected at this range and with this many moving pieces. Clearly it will take some time to lock in the results, but at least for now, we do have a period to watch upcoming. Whether anything results is pure speculation. Given how this winter was expected to develop as a STRONG NINA (now backing off that idea considerably, to the point where the Nina may be collapsing imminently), I think this is about as positive as we could have hoped.

I can't necessarily speak for the Philly area, but I know in the western part of the state we have had two Top-10 coldest Novembers in the last three years ('18 - 8th, and '19 - 10th). For the actual winter months, I'll have to go out further than Top-10. The most recent notable record is February 2015 (second coldest ever), followed by January 2003 (11th) and December 2010 (12th) . February of '07 and '14, December of '00 and '05, and January months of '03, '04, and '09 are all contemporary records. However, all of those months are way down the lists in the teens or even twenties. March is barely represented. 2014 is it on the "top" list, and it is way down there (19th). In the Top-18 for cold March, the most recent is March of 1984. Seems March hasn't been all that cold in a long time. Daily and yearly records are harder to find. 1994 is the most recent cold day. Seems the 80s were kinda cold, overall. If we consider certain elements to be cyclical, maybe things will shift back the other direction eventually. Or maybe climate change will prevent that and things are forever different and unpredictable. That analysis goes above my pay grade. TL;DR: One Top-10 in the last 20+ years: February of 2015 (for actual winter, anyway).

The CMC quickly abandoned this look, waiting until the storm was off Maine's coast to wrap it up. The Euro shows a prototypical Miller A path from the Gulf, through Alabama/Georgia, and then setting it up off the Delmarva. The GFS has a very similar setup, a bit more convoluted, but there's no "snow side" or cold sector. It's all rain and shears off south of our area. Lack of cold air definitely is one concern. Seems this one might be an inland NE special. Really, I think 2010 was the last of this kind of storm. Pittsburgh is still long overdue for an 8"+ event.

I have friends in Mercer county that got well over a foot (perhaps upwards of 16-18"). That's crazy. Goes without saying but in areas with lake effect enhancement and/or elevation, this event pushed towards overperformance.

I measured a little over 3" a couple hours ago. The snow was extremely fine down here most of the day, but this last push may get us upwards of 5" or so. No complaints about this event on December 1st. Let's hope it is a sign of things to come the rest of the winter and not the exception. Heck, if we were to hit 5" officially, this storm alone would be more snow than we've gotten in 4 of the last 6 Decembers.

Looks like it should be snowing here, but it's just virga. Column looks mostly saturated so I guess the precip is still too light.

RGEM nails the AGH snow-hole, or inverted bullseye. Lock it in, boys! Also, cut the amounts by 25-50%.

Other than '17-'18 (13.3"), we've had a brutal run for December snow over the last six years. If this season unfolds as expected, any snow early is worthwhile, even needed. This won't be the blockbuster we'd all hope for, but perhaps we can muster a minor event out of it for the first accumulation.

That snowfall map above looks quite familiar...

For 2009, even I got screwed a tad on that one being in the Philly suburbs. Philly measured 23" and I got 12" - that entire winter was full of tight gradient snow storms.

If Wichita Falls, TX is getting a bigger snow than we've seen in years, you know there's something funky going on in weather town.

Long-range models can't decipher a good pattern to save their life, but as soon as a bad one appears: lock it in! You'd think I'd have learned by now that if the Euro shows a bad result, that's the outcome 90% of the time. (Also, if it shows a good result, that only works out 10% of the time). ... What's confirmation bias?

I don't know how others feel, but I prefer a snowy December to snow in March. Kind of disappointing that we've been stuck in this pattern lately where the snow doesn't really show up until January or even February. Still, Pittsburgh is way over due for an >8" storm. Because it isn't unprecedented, I'll consider this some relatively short-term trend. There have been snow lulls in history, extended ones usually followed up by a massive season of >70" total. As an illustration: Six of the last eight years we've had more snow in March than December. The long-term average still favors December, but they are close.

Yeah, I get why they were complaining (I think they were at historic levels of futility for snow), but everyone knew they'd play catch-up before long. Some people just need perspective, really. There's quite a few in the MA forum especially that would go insane living here. I can't imagine some of those guys making it 10 years without a double-digit event.

This just about sums it up for us. Welcome to the Screw Zone™ for all time.

The more these rain storms occur, the more I think this just isn't our winter. It was 0F last night and is close to 50F today. The atmosphere wants to rain here and that's it, as evidenced by our wettest year on record. This is a harsh pattern we've been set in since mid-2018 probably. If we're lucky, we'll dry out just in time for next winter.

We're well below normal so far (if we finish that way, it would make 3 of the last 4 winters). I agree that expectations for this winter were high. Things looked to align, but at this point, we're going to need a backloaded winter. The blocking that I think we require continues to be two weeks away in the long-term. Maybe by February it will actually coalesce. I'm hoping we don't revert to a bad pacific pattern or lose our moisture conveyor if the blocking comes together, but that's always possible.

Always a bridesmaid ...

I don't mind transient warmth in winter so much, say a day or two in between pattern flexes. I'm not a huge fan, however, of two to three weeks of the doldrums. Maybe we have once chance as the "new" pattern shuffles, but it doesn't look all that promising right now.