MAG5035

Generally in agreement here. While not completely flipping the EPO, ensembles have been at least neutralizing it some as it's gotten out past next week. It's a key thing to happen, because we do have an issue of source region of cold initially which likely manifests in the coastal later this week probably not getting cold enough at the low levels for much snow in PA (more likely toward interior NY/New England) and probably the next system of note that comes about later next week. But you can see it on the models.. once they build any semblance of higher heights on/just off the west coast, it's enough to get the eastern US right where we want it. With that block over the top, we don't really need a raging -EPO ridge to succeed (though an EPO ridge would be nice). We just need to tone down the Pac jet enough as to not flood the CONUS with Pacific air under this awesome block we have materializing in the NAO/AO realm. I'm pretty confident were going to get there.. it just might be around week 2 of Jan or so where we really start seeing this. The 09/10 comparison is relevant here.. simply because we haven't seen that kind of a strong and stable NAO/AO blocking regime since 09/10 and the early part of the 10/11 winter. What I'm curious to see is where the obvious differences between this winter and that winter take us. Of course the big difference is we're working a solid La Nina vs 09/10's solid Nino. The other thing is the SST anomalies in the north Pacific. I was going to post about this earlier in the month, but then the big snowstorm showed up and that was the big topic. But pretty much when comparing past Nina's of the last 25 years+, you won't find one with the + anomalies in the N Pacific that this one has. Most of them are quite cold there. The most recent Nina in 2017-18 is about the closest comparison but still had more colder water. My big worry initially when seeing anomalies like this going into the winter was the assumption of not much help from the NAO/AO and seeing hostile teleconnections from the Pac side materialize. One could see the potential torch in the making. The blocking is a game changer, and now suddenly one can see the potential from an active pattern and suppressed storm track from the blocking. Back to 09-10, here's what that looked like at this point. The Atlantic and the Gulf of Mexico got even colder with respect to average when February rolled around. But yea, huge difference in SST makeup. I tend to suspect that the much warmer N Atlantic this year might help keep a tighter storm track to the coast and you might not see quite the suppression you saw in the 09-10 winter, which was certainly less memorable in New England.. or Williamsport for that matter if we're talking about this particular subforum haha. There were some folks in here that got next to nothing from Feb 5-6, 2010. It's going to be interesting to see how all this shakes out going through January. If we hang onto the -NAO/AO regime we're definitely going to have chances.

Currently getting a brief period of steady snow early this morning, ahead of what's looking like a really icy New Year's Day later on tomorrow around here.

Models have been pretty solid on this threat for the last couple days once they started sticking that high pressure to our north. The high itself has gotten stronger on the progs too as we've gotten closer. It's a pretty good setup for a straight-up ice event, especially in the interior counties. Mid-levels are easily shot already lacking much cold aloft and the system cutting well west. The fairly strong high solidly anchors the sufficient cold we do have in the low levels. The cutting low pressure is weakening as if lifts northward, so it may draw out the ice longer in the central counties. I'd say this is probably an area-wide advisory event in the making, and potentially a WSW worthy one in interior central/north central PA, dependent on QPF and if sleet is a more predominant p-type during the first part of the event. Canadian joined the Euro today having that kicker system right behind this potential ice event. Both were very marginal in their cold air availability for snow (Canadian somewhat better).

With the EPO/WPO forecast to go way positive during at least the opening week of January, I don't think we're going to live up to this high latitude blocking pattern's potential initially. An active Pac jet (+EPO/WPO) is going to ensure trouble in getting access to any decent cold into our part of the CONUS in a pattern that had already been kind of lacking it since our big snow event with the exception of the couple days in the aftermath of the X-mas eve system. If we break this down, or better yet get a -EPO ridge to build.. then you force a better alignment from a colder source region (such as NW Canada). That coupled with the high latitude blocking in the NAO/AO realm.. ideally shifting westward a bit in time would provide a much colder pattern and a suppressed storm track that is less apt to try to cut in the east. We're just not fully there yet. Personally, I'm eyeing up the second half of Jan more than the first half and considering anything we do score in the next two weeks a bit of a bonus. We have a pretty decent strat-warm event seemingly in the cards in the first part of January and it usually takes a couple weeks to start realizing whatever the results are in terms of cold air outbreaks in the mid latitudes. The -NAO/AO regime is looking like more of an overall theme rather than just a passing fad and pretty much couldn't get a more opposite look from what was just getting warmed up this time last winter up in that realm. This significant of a NAO/AO blocking regime was not something I was expecting to see out of this winter. Barring a major change up there or the MJO suddenly busting out into a strong 4-5-6 pulse (currently not looking very likely attm), i'm fairly confident in saying that we're going to eventually see a really good period of winter weather set up at some point.

Might not want to sleep on this New Year's event potentially becoming some kind of a wintry mix event in C-PA. Models have been toying around with sending the first piece up into the lakes, pulling a front across and holding back a good bit of energy for another wave to roll up. While the southern wave builds, models have been getting some high pressure in place over us/just to our north. Positioning of the mid-level features (850 & 700 lows well west) definitely aren't looking ideal for an extended snow event, but get that high over us for at least a bit and we probably are going to be dealing with some kind of messy mix event on at least the front end.

You guys definitely killed it this month over there in western PA. If we can speed up by about 12hrs what appears to be a really similar situation to yesterday shaping up on New Year's Eve/Day, maybe there can be some snow added to December's total haha.

Merry Christmas everyone, it did somehow manage to be a white one here.

Straight-up moderate to heavy wind driven sleet at the moment, maybe a couple flakes. Starting to accumulate and deck's starting to freeze.

There's two boundaries that are noticeable on velocity images. One associated with the thin line of intense rainfall in the warm sector (impacting H-burg and LSV) and a secondary boundary further west, which i've noted with the blue dash.. that is the actual cold front boundary.

I still don't think much makes it over to the Sus Valley but we'll have to see how much precip hangs on behind the cold front. Short range guidance like the HRRR and NAM haven't had much lingering by the time it's cold enough. There could perhaps be enough to witness a changeover period and perhaps a coating in spots in the region east of I-99 over to the Sus Valley. The big thing to watch first thing tomorrow morning is for untreated stuff to freeze up.

Changeover is starting to occur. Sleet, rain, maybe some wet flakes. Temp back to 35ºF.

Frontal passage has occurred here, pretty decent gusty winds. Temp only got to about 41 or so during this whole thing today (about an hour or so ago) and it's back down to 38 already. Frozen precip shouldn't be too far off.

It seems like the most significant flood potential focuses on the Susquehanna main-stem (and NE PA tributaries), especially in the Upper Sus Valley on into NE PA where that particular region has the trifecta of significant rainfall, the most significant existing snowpack, and a several hour period where warm temps via southerly flow punch up into eastern PA to further enhance a more rapid snow melt. Short range models like the NAM have been downright excessive with rain totals, and the next several hours this evening will reveal if that comes fully to fruition as radar trends look to be starting to focus the heavier rainfall rates into eastern PA along the Susquehanna. The other major tributaries coming from the central counties (West Branch and Juniata watersheds) look to have a significant rise but most point forecasts appear to stay below flood stage along those rivers. Temps in this part of C-PA are locked into the upper 30s-low 40s and as mentioned, heavier rainfall is starting to focus towards eastern PA. Appears that any surge in temps in the central probably comes close to/with the frontal passage as the stable b-layer gets mixed out. Lack of big time flooding coming from those two tributaries probably prevents the main stem from going full blown '96 repeat in lieu of a more minor-moderate flood event coming primarily from upstream in NE PA/southern NY. Definitely not ideal anyway you slice it, what an ugly Christmas Eve weather-wise.

This lead up to the Christmas holiday is definitely looking like it's going to deliver a hard lesson about most of this region when it comes to December snow. Something to the tune of the only guaranteed White Christmas is one where it's snowing on X-mas Day haha. I'm not sure that the portions of north-central PA that got the tremendous totals are going to see a complete pack loss but it's going to get a pretty big dent in it from the Christmas Eve system while the rest of us probably lose the majority of it. Just was hoping to avoid that long drawn out event with the strong cold front but we're going to get a pretty good dumping. Still a bit uncertain about any changeover, that seems the favor from the Laurels west in PA currently and it might be even further west than that with the possible snow swath. Models drawing that secondary low pressure wave that rides up the front through the middle of PA is a pretty good recipe for a slot and shutoff of most precip by the time the cold air's all the way in. At least this storm system will be a one day affair and send some pretty decent cold in for Christmas Day. Then heading towards New Year's we have a good pattern setting up with the nice -NAO block and overall high heights near the pole. So good chance we'll have one or two shots at an event between Christmas and New Years. Here's the possible problem I see, and we got a dose of this problem the last couple days. I'm kinda worried about the amount of cold air we might have in this said favorable pattern. A look at temp departures of our source region in Canada on the models shows a fair amount of above normal temps and not really any bouts of big time cold building with respect to average. Obviously, above normal in Canada is still "cold", but that air mass modifies as it gets to our neck of the woods. I'm hoping we don't waste a couple serviceable storms on account of not having good surface temps to work with (see the last day or so).

Same, it leveled up at about 34ºF most of the night last night and it hasn't been below since. Def shrinking the pack some here (which has no sleet in it). The active northern branch on the heels of the big storm has kept temps moderate at night with the exception of the one clear night Saturday Morning.

1.5" this morning and still snowing lightly.

Might get a period of light snow this morning over there but probably little to no accumulation off the mountains as best precip hasn't been progged to get much further over than western PA (although this is def overachieving here). It appears the clipper might have a better chance of delivering lighter accums (up to an inch or so maybe) out to at least some of the Sus Valley, despite clipper low track going a bit to the north.

Snowy start to the day here, working on an inch and a pretty good burst of heavier snow currently.

Yea, this was why I didn't like seeing the more amplified solutions for this particular system. I'm a build the snowpack kinda guy when it's DJF, I hate starting over lol. Euro op dumps a lot of rain on spots with the big time snowpack, and in general really. Progresses much slower with the front, dragging this affair into the first half of Christmas Day before the cold air gets back in. GFS on the other side of the envelope getting cold rapidly back into pretty much the whole region on Christmas Eve before midnight. Doesn't have as much rain as the Euro and has been the one leading the most with that anafrontal type deal. Still punches LSV into pretty warm temps for several hours. All in all it looks like a 12-18hr period encompassing most of Xmas Eve where temps get up into the 40s-50s in most of the region. I just want to get the front through as fast as possible.

I took mostly hourly snow observations through the duration of this event so I experimented making a couple charts. Top was the snowfall rate per hour and the bottom was the running total with the hourly rate also part of the graph.

On the X-mas eve system/arctic front passage, not to be pessimistic but Models shifting toward the slower, much more amplified solutions is definitely a case of be careful what you wish for. For our region this may work out in western..perhaps some of interior central PA but I personally don't see much upside to this in the Sus Valley. GFS is the better scenario, focusing on the second wave running up the frontal boundary. Yea there's some snow to be had but it also delivers a ton of QPF (a lot of it rain) beforehand in eastern PA. Euro's even worse with more of a straight up lake's cutter and less emphasized secondary low that probably wouldn't change precip over in time for much. That sends a bigger warm push and 1"+ of rain into places that just got a boat load of snow before maybe a few hour period of snow at the end. All in what you want I guess. You might see that period of snow at some point X-mas eve to X-mas morning, but you might lose most of the pack to see it. I'd rather see the front progressed through faster and maybe set the next event up. Pretty far out in range yet for now, but it does seem like models are heading toward making this more of a QPF laden event. In the meantime there is a couple other weaker systems (Sun/Mon, and Tuesday-ish) to resolve, as one of those systems could muster up enough to put a swath of something across a part of the region.

I'm trying it out a bit. Main thing I'm having trouble with is it loading the radar image really slow.

Plot twist, it's snowing again tonight here.

Same here over on this side of the Laurels, got a fresh coating so far. Pretty nice aggregate flakes too.

You guys seeing much out of this patch of snow in the western half of the state this evening?