MAG5035

This system in the longer range slated for early next week seems to be solidly in all guidance now in the general sense. All the op guidance last night tried to cut it to some degree, making messy solutions. Todays 12z GFS was more of the same with the Euro and Canadian now having a colder/weaker solution that does slide south and is all snow. GFS's deeper solution has more amplification and some northern stream interaction while Euro/Canadian run a weaker shortwave wave out with no interaction. One would have to worry more about suppression with the latter given the blocking. Either way big differences in the afternoon suite. I've def been as optimistic as the next person with this upcoming pattern but i've soured a bit the last few days on some aspects. I'm not a fan of the evolution that has come about of retro-ing the pac ridge far enough west that it dumps the main trough into the western US (aka solid -PNA). Yea, with the strong NAO block the storm track will generally try to stay under us but I see limited phasing/amplification opportunity and if you do get it lined up/amped enough to get something like the stronger solutions from last night or today's GFS, they will try to cut. That brings me to the next problem, temps. Now if this potential system does try to cut into the block... it's likely going to weaken and/or transfer, and normally i'd favor a mostly frozen outcome even if the primary did get west of us. Problem is we currently don't have an actual solid cold air connection, and if that main trough dumps into the western US right when we finally see negative anomalies with some teeth building in Canada.. we're not going to be much colder than we are now as a lot of that cold will dump into the trough. So my worry with even the scenario of a stronger system with miller B evolution is we don't have strong enough antecedent cold to stave off a messy wintry mix type event over what normally could be a mainly snow event. Obviously a weaker system like the 12z Euro/Canadian wouldn't have the precip issues as we maintain colder temps, but the weaker system would be more apt to get outmuscled by the -NAO and only give us a lighter event or even a southern or suppressed one. Climo's on our side this time of the year with seasonable or marginal temps but we're going to get bit if we don't get some legit arctic air involved in the pattern. That goes double for the Mid-Atlantic region and the southern fringes of our region that can pretty much be an extension of the northern Mid-Atlantic climo. Current case in point... despite passage of a pretty deep trough where at 12z tomorrow morning there's sub 528 heights and sub 522 thicknesses across most of the state in mid-January, we're still going to be above average temp wise. That's something that normally could equate to a day that has highs in the teens to 20s-30ish NW to SE across the state with a run of the mill cold airmass. Harrisburg is forecast to still hit 41 tomorrow.

Heavy squall currently, getting everything whitened back up.

The two periods I have an eye on are D5-6 and D9-10 range. There's also going to be some weak shortwaves in the flow early this coming week but will likely primarily deliver periods of snow showers/light snow to the Laurel's and western PA. For the D5-6 (Thursday-ish) there's been some solutions that amp the northern branch just enough to generate a wave of precip to move across PA, esp on the Euro. This would probably be a light event if it occurred. Something's likely going to come out of this D10 range, but hard to say what at this point obviously. So far today the GFS and Canadian have something notable, but differ in the pattern somewhat. GFS dropped and phased a shortwave out of Canada making the huge storm it has. Canadian doesn't phase and also dumps the trough in the western US raising heights and making a more messy storm that tries to cut.

It's been dry so far this month, or essentially the last two weeks. But we were coming off a very active period with the big mid-December winter storm, the significant Christmas rainstorm/flood, and the New Years and Jan 3rd systems that delivered various types of precip (and another decent snow up your way). That's a pretty busy 15 day period. Drought monitor only has a small D0 area in a portion of the Mid Sus Valley, likely dealing more with the short term dry conditions of the last couple weeks and dead vegetation drying out. We had seen solid improvements in the drought conditions in the late fall going into last month and the aforementioned active period pretty much eliminated it completely with no part of PA having actual drought conditions. North-central had been dead center for the worst of the drought conditions this fall and that very deep snowpack from the snowstorm was a big part in helping eliminate it.

Nice burst of snow currently, too bad it doesn't look like it's going to last too long.

I don't see too much in the upcoming shift in the overall pattern that argues we don't start seeing the results of the ongoing strat-warm event and continued -NAO/AO blocking. I've said a few times my eye has been on the back half of Jan, so this is materializing on time IMO. The EPO realm has been about the only sticking point, with persistent low heights in the Gulf of Alaska cutting off the source region for cold. That's set to reverse at the end of the week, with models/ensembles first building a ridge on the west coast eventually evolving to a full blown EPO ridge. Very strong and remarkably persistent ridging anchors over Greenland and that forms the bridge over the top when that -EPO ridge really cranks. So in sort, the table looks set for the arctic to invade the US in the next 1-2 weeks. Longer range seems to retro the EPO ridge further off the west coast, putting the western states in the trough and cold as well (-PNA), which with the strong -NAO/AO to fend off any significant SE ridging could help not completely squash our storm track with some actual arctic cold injected into the pattern. We're going to get the colder pattern, so the big thing will be what kind of storms we can get out of it. I think we'll have our chances. One thing to watch is a frontal wave on the arrival of the start of this colder period this coming weekend. Models are starting to show a coastal low popping (and winding up getting up toward New England) and they all have some precip in at least the eastern half of PA with the wave.

Hot take on the 0z 84 hr NAM, too bad the DGEX still wasn't around.

I like how they have a category for "type" of snowstorm. Like one of H-burg's top 5 snowstorms was going to come from a clipper or something lol.

The overnight 0z guidance looks to be showing that this Tuesday system now in the D5 range for us might have some legs...with Euro and Canadian presenting a snow event over a good portion of PA and 0z/6z GFS not too far off for PA but still showing a fairly competent low trying to lift out of the Gulf states after developing in Texas. Difference with the GFS vs Euro/Canadian is GFS keeps streams separate and the Gulf system as a single southern stream shortwave. Euro/Canadian drop in and interact a northern stream shortwave just enough to make this more of an event. Ensembles showing the system but not very strongly yet when it comes to maybe running the low up the coast to impact our region. Euro EPS was probably best look, but we'll see how things evolve as we're still D5-ish. I do like the look and the fact models are latching onto having something of substance. These Gulf lows can be more moisture laden than advertised, so if we can work it up to our latitude I think we could see a decent snow event. It's definitely starting to look like it could be one at the early stages all the way in the heart of Texas.

It stopped snowing around this time in the afternoon Sunday. It has remained cloudy and literally within a degree or two of 35ºF in the 72 hours since then. I dunno about any of you guys, but I'd actually like to see some sun and clear weather for a couple days.

Like I said this morning, I think this stands a better chance than Friday's event which is now pretty solidly looking like a southern slider. And also as mentioned, models are wildly inconsistent with it. I had mentioned this morning about the 0z Euro basically having no system and you see what the 12z did. The overall pattern is better for the potential of the coastal storm, the big difference being the western ridge has really built in this timeframe along with some lessening of the dominance of the NAO block. That forces the northern branch to finally try to drop down in the east (dependent on how much amplification) and allow a potential phasing opportunity with the multitude of shortwaves running around. The Euro obviously succeeded at some phasing at 12z and I don't even think it was a complete one either. Can actually count up to 4 different shortwaves involved at one point in the early stages of this (135hr frame in this example), although ultimately it looked more like a typical phase once to the timeframe of initiating the coastal storm. Now I'm not saying "OmG QuAdRuPlE PhAsE" here but it's a good example of the overall chaos and why we're seeing wild swings in model runs with a lot of imbedded shortwaves. Basically it's the classic "storms and rumors of storms" setup you see a lot with established -NAO and some western ridging to go with an active pattern, which models usually have a lot of trouble with especially in the mid range. GFS seemed to keep the streams more separate but there's still a bunch of shortwaves in the flows with some different timing. Result is not much interaction and no coastal storm. Gonna be awhile til we see anything firm on where we go with this potential, but in the meantime we'll have to watch the next couple days if we get an overall storm signal out of this on a majority of guidance or if this fizzles completely.

Friday's system is definitely shaping up to get blocked well under us. I thought a couple days ago this may eventually come back up enough to swipe at the DC region or perhaps even into the southern tier LSV. But now it's looking like interior southern VA is as close as it gets. Name of the game whenever you have a significant NAO/AO blocking regime, we're gonna lose some stuff underneath us. This system's coming at the point when teleconnection forecasts are generally at their most negative for the NAO in the forecast period (about a -3 on the WB forecasts). There's also isn't much western ridging to really amplify the system either at this point. The next system being progged out in that D6-7ish timeframe probably has a better shot but hasn't been really consistent. The overnight Euro for instance pretty much didn't even have it. That may end up being south too but I think it's a better chance for at least the Mid-Atlantic folks to get their first system, we'll see. Still looking at the bigger picture here, I said a couple previous pattern posts ago that I was eyeing the second half of Jan more than the first half and I would consider scoring a snow event in the next couple weeks to near mid month a win. And really it has been even if some didn't get snow out of Sunday's system. Take away the dominance of the blocking regime we have in the NAO/AO realm with the current look in the Pac with that +EPO and very low heights in the Gulf of Alaska and we probably have very little chance in what would be a much warmer regime. The blocking is suppressing the storm track and providing just enough marginal cold air (in what really isn't at all a cold pattern) with the Pacific air flooded CONUS to give us a chance with each system the next 6-10 days. I think the system after next has a better shot since it seems we tone down the NAO/AO a little bit and it's in the timeframe where the Pacific/western US side of the equation is starting to look more favorable. Models/ensembles have all been showing a big shift in the Pac, building ridging in the EPO realm up into AK where we have very low heights now while keeping a -NAO/AO. We need to inject some actual Canadian cold into this pattern and that's how it gets done. This is also a better alignment to involve the northern branch better with any potential phasing opportunities. Here was the overnight Euro ensemble for 12z this morning, D7 (near the timeframe of that second event) and D12. Look how much the Pac improves especially between the D7-D12 ones. The GEFS is doing the same general thing as well. Shaping up to be quite wintry after mid month if that comes to fruition. Current: Day 7: Day 12:

Slotted out here at 1.1", def a really wet snowfall. I'll bet some of that 3-5" the models were cranking out ends up coming to fruition somewhere in between UNV and IPT.

Wow I haven't seen flakes this big in a few years. Pouring half dollar snowflakes in this band.

Passed the 0.5” mark, moderate to heavy rate.

Same here, it didn't take long to start accumulating (on the roads too).

Transitioning over to snow now.

Mostly sleet falling currently after a bit of a damp start to this. Had a glaze of ice on the car first thing this morning. Now to see if this gets to snow quick enough so it can do something accumulation wise.

Still not totally sure what to make of today's system. Looks like two different waves of precipitation. Surface temps have cooled off nicely overnight and most areas near or below freezing. However, temps per mesoanalysis at the 925mb (southern third of the state) and 850mb level (most of the state) still above freezing. This means the initial wave of precip arriving later this morning likely to be a mix, which is the main basis of the advisory for the Sus Valley (for the possibility of a T of ice). The second and probably main wave of precip arrives in the afternoon associated with the upper level low itself. Under this is where we have the cooling at 925 and 850 to support an all snow column. Track of the weak mid level low features seem a tad NW to me, thus I kind of support CTP having the best snows from UNV on to the NE instead of LSV locations like MDT. This could cover more of the central counties depending on how precip develops though. Near term guidance has generally been putting the best QPF from the upper level low from the central counties to NE PA. Dare I say Williamsport appears to be the new snowtown these days haha.

Was able to get a couple general measurements of the ice. Looks like about 0.2" of ice accrual. Temps still hovering in the 33-34ºF range.

I upgraded to an iPhone 12 Pro a few weeks ago, it has one heck of a camera system. Really excels at the low light stuff, and also showing we’re still in the thick of the icing phase of this system here.

Have had some sleet occasionally but all freezing rain currently. Starting to be pretty noticeable on the trees. Have a feeling this is gonna end up more towards a warning level ice event.

You only need a T of freezing rain to verify a WWA, which is fairly likely even in H-burg.

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.