jwilson

The Euro control and EPS both were north of the OP this morning. That's a bit of a red flag at this juncture. I'd bet even the Euro and Ukie maps - which look decent enough - look much worse if you filter out sleet. The NAM basically gives the metro area a foot of sleet. Wouldn't surprise me much if a lot of that turns to rain in real-time. My confidence is waning. I haven't jumped off the bridge just yet, but I have my toes to the edge.

Well, the good news is the Euro and Ukie both stayed south and worked a transfer to the coast (again). The Euro gives us almost zero breathing room. I would think, with the tight gradient that close, those of us south of the city probably get some mixing. If not rain, then sleet. The Ukie looked a lot like the 12Z Euro from yesterday and is much more comfortable. The bad news is the NA models are adamant about a stronger phase and cutting the low up into Pennsylvania. The GFS is consistent, at least, and only gave us something notable back on Sunday. Since then, it loves the interior New England special. The NAM is a bit closer to workable, but still brings up too much WAA. The ICON has moved south, though the evolution is a tad odd, with multiple lows on the boundary. Despite the move, it again begins phasing too soon and pushes a southerly flow north. I can't think of any examples off the top of my head, but I'd be curious if anyone has recollection of a storm where the propagation of the warm tongue stopped between Morgantown and Pittsburgh. Perhaps say as far north as Washington.

Unfortunately, I have to think cwc is correct. Anything remotely borderline and we'll probably lose the fight to rain. Now I haven't been living near the city long, but I'm very familiar with the warm tongue, and I don't see a fresh source of cold air to keep it at bay (unless there's something I'm missing). If the primary tracks on a line from Kentucky to WV, we're probably warm. If it goes through Tennessee and waits until Virginia to pivot or transfers to the coast, we may be okay.

0Z NAM - still at range, mind you, so somewhat limited utility - has the primary low crossing through Kentucky. That's too far north. Huge WAA surge in the end. There would be a snow to rain to light snow scenario. Not a great solution, pretty much blends the GFS and Euro. Unfortunately, we basically need all Euro.

NAVGEM has a strong progressive bias.

That's a good point. I really don't know much about these off-hour runs. However, the 6Z continued the 0Z movement which ran into 12Z. For the 18Z to go back the other way makes me a tad nervous. Perhaps we won't like what we'll see at 0Z, or maybe it's nothing. Here are the last two runs compared: You can see the gradient has moved up into southern Allegheny. Of course, the snow isn't entirely finished in the bottom run, but it's probably done for our area.

18Z Euro a slight tick north, more in-line with the Ukie. I realize it was relatively minor movement, but we don't have much more room to go in that direction. I suppose the relative consistency of the GFS since Monday shouldn't be discounted. I guess we'll see how the 0Z runs go, but any more northward shifting and we're in barney.

I don't normally trust the NAM at range. It does show a potential outcome, however, where this is more of a frontal boundary system that moves through and ends without redevelopment. The GFS cranks that initial wave from Thursday as a 50/50. The NAM has less confluence. I will say I'm not sure if the NAM would actually be done when it cuts off, as it might still try and develop a secondary low offshore. Of course, it would probably be too late to give us more snow, but it could come down to timing. The Euro and its ensemble members are clearly favoring redevelopment, seems right around New Jersey, and that's part of the reason it has less of a rainy influence.

Yep, time to hug the Euro. Sadly it is on its own. Even more south of the UK. 16" in Allegheny. Best model to have on our side, but I have to wonder if it is downplaying the warm-air surge while the GFS is over doing it.

You are correct. 1950 is #1, actually, with 27.4" of snow. The fact that the biggest snow for the area occurred in November tells you all you need to know, really. In fact, Pittsburgh hasn't even approached a 20" storm in January since 1886. Basically, it would be unprecedented.

2010 pretty much. 2016 was close, but the gradient ran the other direction (from south to north). Areas in northern WV got >20" but I think the city saw less than five. Pittsburgh only has four storms in history that have exceeded 20" of snowfall. Too far west for Miller B's and usually too far northwest for Miller A's. Plus the orientation of the Appalachians means a warm surge of air rides up the western spine if lows get too close. The opposite of CAD. Kind of a terrible place for big snow storms.

12Z roundup so far: High-res NAMs look like all snow for tomorrow's event. The GFS is less certain, poking in the warm tongue. City on south would probably mix verbatim. As for the weekend, the GFS remains consistent with a north and more phased system. FV3 and Icon much the same as the GFS. The Canadian is going to look the same once it gets out to range. The overnight run of the Euro was a continued improvement from 12Z yesterday, we'll have to see if it continues that trend or folds to the GFS. The Ukie last night was also much farther north than yesterday's runs. Overall, I think this is one of those systems that comes down to the wire. Meaning: even as the event starts, we aren't quite sure what we're going to get. We have working against us a lack of fresh cold air, as evidenced by the shortwave that may not even stay frozen, and zero blocking. We don't really have that banana high anymore, either, until late.

Not that it probably matters much, but the 12Z JMA was a tad south, as well, but not as far south as the Ukie.

The NAMs at range look like all snow for that pseudo clipper Thursday. Won't be much, but hopefully it stays all frozen. There were improvements on the Euro at the upper levels, so not all is lost, but I'll be extremely concerned if the Ukie folds to the Euro/GFS camp. Outside of that, we still have to get into NAM range for the main system to completely give up hope. Things certainly not ideal right now.

Euro is brutal. Over 65 miles, you go from 2 inches to 24. Unfortunately, it's been somewhat consistent now. I'd feel a lot better if it was flopping between solutions. If we could ever get the blocking and this juiced southern stream to connect, we'd be fine, but we'll probably lose the moisture as soon as the blocking kicks in.

As far as I see it right now, we need one or two things to save this one from going north like the Euro and GFS intimates. Either the low remains less amplified and more strung-out, and perhaps delays amplification until it gets East of us (seems unlikely given the overwhelming model "consensus" this early), or we get a northern stream pulse, some kind of PV lobe to help suppress the low to our south. We don't have much in the way of blocking which is a serious problem, but we do have an advertised banana high, which may be too far north, and a potential 50/50 low to slow progression, which is the evolution of the Thursday/Friday shortwave. Oftentimes with these bigger storms, you'll see a table-setter event that basically portends where the snow will fall. As it looks like the pseudo clipper will push too far north to prevent a changeover, I worry the storm behind it will follow the same path. That second low would look better in Tennessee or even further south. If it tracks right over Kentucky, we're in trouble. I'd rather have one of the GFS or Euro on my side right now. I have much less confidence in the iCON and Ukie.

That's really not unusual in this time frame. Large jumps in precise locations are relatively normal 4-7 days out. If it still looks like that come Thursday or Friday, then we can be concerned. Aside from that, the long range is showing some REALLY cold air dropping into the CONUS (as low as -22F locally). That will probably moderate in the mid-range, but we could see some bitter temps.

The good news is the seasonal trend has been to shift things south closer to the deadlines. Of course, with the pattern change, undoubtedly that trend will get flipped for the opposite when it no longer could favor us.

I used to chat on those forums in conjunction with this site (which used to be easternuswx, as well). Been a while since I've been there, though. As for this weekend, I'm not buying any single OP solution just yet. All the finer details will have to get worked out as we get closer to the event. The most important note right now is that there is a signal for something big, and a pretty alarming signal at that - showing up on quite literally all the models a week out? Pretty incredible and honestly, rare. Being in the bullseye this early would be difficult to deal with, though. Don't want to get too invested in this system given the rather unusual path it could possibly take.

I like the period after this weekend a lot more. Say between the 19th and the end of January. I think we get at least one significant event in that window (6" or more). This upcoming storm may still provide something, but I see it as more of a table-setter than the main course.

Well, that first suppressed system brought in this current dreadful pattern, maybe the second version can usher in the pattern reset? Progressive, flat flow and southern stream looks shuddered by a strong NS vort. Wouldn't surprise me to see that high pressure drop south as we get closer. Teleconnections pretty marginal. I'll be flying on Sunday so I'm okay with this one missing. Edit: FV3 and CMC are still showing a possible storm solution. Perhaps a big one at that, but until they get support, I won't trust those two alone.

FV3 has already teased us with some digital KU classics this season, only to fold to the old crowd closer to the event. Not buying in yet. I am a bit apprehensive about the FV3 replacing the current GFS, however. Seems - at least over the last month or so - it has a penchant for showing a big tease too soon. For 300 hours that's typical, but a week out? Hopefully it's nothing.

At this point, odds would favor that it should snow in January. Basically, getting shutout would place it in the bottom 5% of winters. Of course, things can theoretically recover in February and March. I don't expect a 2001-02 repeat.

Whoops. Well, if that ends up being the total come the end of January, it would pretty much fall in line with those two outlier years moreso than the other years with multiple - but small - events. I mainly meant to discern how rare it was to be shutout (or nearly so) in both months. So far this year looks closer to the low-end extremes. Hopefully not to be repeated soon.

Out of curiosity, I was looking through records for when the last time PHL failed to measure snow all of December and January. Recently, 2015-16 was pretty bad until that one large event salvaged things. Without it, both months would have had 3" total (none in December). 11/12 - 2.5 total (none in December) 07/08 - 2.6 total 06/07 - 2.2 total 01/02 - 4.0 total all winter (zero snow in December, Feb, or March) 97/98 - 0.8 total all winter (I remember this stinker) 96/97 - 1.7 total 94/95 - Here's your true winner. Technically, there were three "Trace" measurements in January, but other than that, total shutout. I went through 1968 and found one more year of zilch (72/73). In fact, as far as I can tell, the winters of 1972-73 and 1997-98 are the two worst on record in terms of snowfall. So, in the last 50 years, only twice has there been no real snow measured in PHL between December and January. By that I mean anything other than "Trace" events. Although, it is more common than I would have expected to see one of the two months between December and January to get next to no snow. It looks like this year could be another in that list.