MAG5035

While CTP isn’t showing too much in their winter products at the moment, you might be in line for some snow New Years Day along with the Laurels as a shortwave drops through from the lakes. That might bring in a period of steady snow that could put down an Inch or so west and NW of KAOO-KUNV and what might end up being advisory worthy numbers in the favored upslope areas of Cambria/Somerset. There’s also likely to be a period of snow showers tomorrow in the western half of PA.

Decided to pull this back up, my last pattern related post 9 days ago back on the 19th. So this has generally been on target I suppose… and I continue to think any big time cold happens mid Jan on. What happens in the meantime is up for debate. It’s looking more like the same type temperature pattern over the CONUS and Canada into the first week of Jan with significantly above normal temps in Canada and northern US and average to below the further south in the US you go. Our neck of the woods looks seasonable to somewhat above, but likely cold enough that a reasonably tracked storm opportunity might be doable. That timeframe seems to be in the Jan 4-6th realm. Ensemble guidance has been roughly suggesting it and the new 12z Euro op just about pulled it off. There’s been really poor run to run consistency with op guidance.. especially with the GFS. There’s big differences in the mid-range to D10 between the GFS and Euro just on this current 12z cycle, with the Euro being much colder. At any rate, here’s my concerns about the pattern getting into week 2 (second week of Jan). The pattern is certainly changing heading into this period. The big thing is the significant warm anomalies in Canada disappear and are replaced with cold anomalies. So that’s a good first step. Teleconnection wise, ensemble guidance has been developing Greenland blocking and injecting actual cold into the CONUS. All ensembles show solid -NAO/AO. Here’s the issue I’m seeing… The PNA which has been pretty positive as of late reverses to negative around that Jan 4-6 timeframe. The EPO goes into a positive spike, specifically on the GEFS…but in that same timeframe. The magnitude difference could be why the GFS/GEFS has looked a good bit warmer in the east… along with much less high heights over Greenland. But either way, the main three ensembles show the flip to negative PNA. My main concern with this is that the cold that’s finally on the table focuses.. at least initially.. in the west and central. That can still be a good thing if we have the solid -NAO since that would probably keep us near the storm track while having sufficient cold available. It could also suck if it’s more of a GEFS evolution (less Greenland blocking and -NAO) where the mean trough axis is too far west popping up heights off the east coast (making us prone to cutters). I do think if the latter scenario happened that the cold air still eventually comes, but delayed (again). 12z Euro EPS v GEFS 500mb (5 day avg D5-10 anomalies). Note the much more pronounced + heights over Greenland on the Euro Euro EPS v GEFS temps ( 5 day avg D10-15)

Yes and no. Doing 10/11 to 19/20 Philly averaged about 24” a season to UNV’s 34ish. 24” is about PHL’s 30 year avg and 34 is about 10” less than UNV’s 30 year avg. So if you were going off of departure from the station’s average, then yea PHL had a better decade. I’m sure the average deviates some whatever you consider for the 2010 decade. If you went for the true decade you’d be splitting winters (starting Jan ‘10 and ending Dec ‘20). The big takeaway though is that PHL outright outsnowed UNV on what would be considered the snowiest winters of that decade.. and I’ll throw 2009-2010 in there. 2009-2010 (78” to 49.1”), 2010-2011 (44 to 38.4”), and 2013-2014 (68” to 51.8). They also outsnowed UNV off the one hit wonder 2015-2016 season (27.5” to 17.9”). If anyone could’ve made it out of Harrisburg the 80 miles or so up 322 on Jan 24,2016 you would’ve found that State College had a 2-4” snowfall depending on what end of town you were.

I definitely like the look of the pattern from a 500mb standpoint with the below average heights over the southern US with above in Canada, eventually progged to center west of Hudson Bay in central (and then western) Canada . We’ll eventually score something if we continue to maintain that suppressed storm track look, which is generally shown across the guidance. My big problem for the time being is temps. It’s going to rear it’s ugly head again with the storm next week that has been pretty consistently on guidance in that Dec 27-28ish period. Gonna try to cut but it looks like it’s going to be forced to reform on the coast. If say today’s 12z GFS scenario played out there’s no decent antecedent cold air in place with the initial low trying to drive well west and the coastal beginning to form and it’s too far displaced N for the northeasterly flow of the coastal to draw it down (similar to what just happened). That storm looks to be a part of the overall pattern reshuffle but I don’t think we’re going to have a snow threat out of it, certainly not in the Sus Valley but probably not in this part of PA either. Notably above average temps in Canada and X amount of the Northern US depending on the flavor of longer range model guidance (weeklies, GEFS extended) has been a constant theme. As such I don’t expect a big time arctic air intrusion probably thru at least mid month Jan. Not that we need it, but the big thing that you can see now in regular ensemble guidance is the 500 ridging shifting to western Canada by about New Years. That would at least ensure airmass source directed from Canada and not the Pac, which should get us cold enough to pair up with a storm track which has honestly been pretty favorable for us this season so far.

32/27ºF with light snow currently. Coating of snow on the grass so far this evening, with another solid wave of LES/upslope snow working SE in the half hour to hour that should make it off the Allegheny Front enough to probably allow for period of accumulating snow here. I’d say pretty decent chance to get the first 1”+ of the season overnight. I’ve only measured approx 1/2” for the season so far prior to today. Rain total from yesterday was only 0.67” and peak wind gust occurred this afternoon right at 40 mph.

Later model trends in the last 24 hrs or so shifting (or perhaps tightening the western extent of) the heaviest rain axis to the east some ended up coming to fruition. Instead of western PA being the sharp cutoff zone it ended up being in this part of C-PA. Still in the decent steady rain for the time being but only at 0.45” in the rain gauge.

For sure. Flash flood guidance is fairly high especially in eastern PA, but this is still likely to cause widespread issues of the urban/small stream variety and some of the medium size waterways cracking flood stage. Looking at headwater guidance in the Sus Valley…Swatara Creek looks especially vulnerable for minor or even moderate flooding as well as the Schuylkill River (for minor) given the widespread agreement on a 2-3+” event of which the heaviest bulk likely comes within a 12hr timeframe. The tributaries of the Juniata (Little Juniata and Frankstown Branch) would be similarly vulnerable to at least minor flood stage if the swath of heaviest rains (2-3”) ended up catching back this way. Headwater guidance . 1hr 3hr 6hr 12hr 24hr

One of the big things he’s been pointing out with regards to the Nino is despite the ocean temp pattern itself indicating easily a strong Nino occurring (+1.9ºC as of 12/11 in Nino 3.4)… indexes like the SOI (southern oscillation index) and MEI (multivariate ENSO index) tell a different story. I don’t fancy myself as an ENSO expert by any means but those indexes are utilized to try to calculate the actual strength of the ENSO event atmospherically. SOI values of -8 and lower are indicative of El Niño conditions being present. The values vary day to day but longer term averages typically reflect the ENSO state. SOURCE According to that, the running 90 day average on that index is only right at the threshold of a Nino, while the 30 day average actually indicates ENSO neutral. So that’s a pretty big disconnect right there. Comparable strength Nino’s generally had significantly more negative values. Here’s the MEI values, compared to some of the other strong Nino episodes. MEI is supposed to be a more accurate representation, as it incorporates 5 different variables vs just one variable with the SOI. MEI Website HERE That index isn’t even close to the biggest Ninos (83, 98, and 16) despite being a strong episode but tracking somewhat closer to the other two stronger ones (86-87 and 91-92) as well as some other winters that had weaker nino’s SST wise. Definitely interesting stuff.. but that doesn’t really clarify whether or not we’ll be snowy unfortunately. Using Harrisburg, 1986-87 had 45.9” ( solidly above average) and 1991-92 had 12.9” (turd winter). We’re still really early into this season and as pointed out previously by many…Nino Decembers are typically warmer than average whether you’re using the good or bad winter analogs. We’re still a ways out in terms of the pattern “showing it’s hand” so to speak on what kind of a Jan and February we’re looking at IMO. I’m just touching on one part of a whole bunch of other factors (NAO/AO, MJO, PNA, stratwarm, Pac pattern in the mid-latitudes EPO/WPO, etc etc). I do like the way things are starting to look going forward, but also am staying mindful that this could definitely go the other way as well. And yes the Nino is forecast to eventually collapse later in the spring next year (and potentially develop back into Nina by next winter) but that’s not a really new development and it’s very likely Nino conditions persist throughout the bulk of this winter. What could occur is the Nino becoming more central/west Pacific based (Aka the Modoki El Niño) which is more supportive of the type of winter weather we’re looking for than an east based Nino. And we’ve already been seeing the waters cooling in the tropical eastern Pac (Nino 1+2). Off the ENSO Update issued Mon 12/11

The problem with it I see is the connected low heights all the way to the Pacific, indicative of the WPO that has been and continues to be forecast persistently positive and the EPO after the dip next week around the timeframe of the coastal is forecast to trend back positive the rest of the forecast period. That kind of alignment implies a pretty good dose of Pac origin to our airmass, despite the development of the below average 500mb heights across a sizeable chunk of the CONUS. Yea that’s good for potential undercutting southern stream systems that track under us, but look at the 18z GFS result for the 17th-20th coastal. Looking at a 2-3+” rainstorm in all of PA despite the phasing with northern stream energy and an ideal coastal track via that particular solution. The problem is across the board on model guidance though with that, the cold just isn’t there for it.. not even close. We need to build an actual western US/ Eastern Pac ridge, that would at the least source Canadian air (even though temps are significantly above average for there) to go with the undercutting low heights. Here was the last 5 day (D11-16) avg temp anomalies from that 18z GEFS. By the way, I am not part of the winter’s already over or is going to suck crew. It’s been noted that a lot of forecasters and Nino analogs, even the cold ones featured a warmer than average December over a lot of the US. Even JB said it was going to be warm first half of the month, just that he thought that this was going to turn around the holidays. Which it may, but right now I don’t see a quick enough wholesale turnaround in the pattern for that timeframe (at least by Christmas).

Temps in our neck of the woods have been averaging normal-ish on ensembles thru the 10-15 day period. It doesn’t look all out torchy, but the true big + anomalies are at higher latitudes like the north-central US and most of Canada. Clear indication that anomalous arctic cold is out of the equation on our side of the NHEM for now (it’s over on the Asian side). AO/NAO have been forecast to be increasingly more positive during this next 10-15 day range and ensemble guidance, esp the Euro EPS really show low heights over the poles and high heights over the mid-latitudes. EPO is forecast to take a dip negative which could help draw a source region from Canada, but there’s no “cold” there.. so what comes down only would be seasonal for us and not below average until say the southeast US. We’ve also been traversing phase 4-5 the last several days in the MJO, which is forecast to be heading in the null phase the next couple days. That jives fairly well with our recent period of being above average temp wise. To sum all that up, we’re not there currently for sustained cold and snowy.. or even really stormy at all for that matter. The main weather feature to keep an eye on during the whole forecast period for op guidance is the potential southern stream system thats been modeled around the 16-18th. Most guidance has had a fairly potent, slow moving coastal system near or up the coast… the problem of course being there’s a lack of cold air for it. This could eventually come back to being an interior/elevational threat for snow as guidance is able to hone in on it more (obviously dependent on track) but I don’t think there’s going to be enough cold around for places like the LSV and Mid-Atlantic with that particular system.

Light coating on the grass here at home. Looks like I’ve succumbed to the back edge though so that may be it for me until the NW flow stuff starts setting up overnight and early tomorrow. Took the 5 mile drive up to the top of Wopsy and there’s a couple inches pasted to everything up there. About put the Subaru in the ditch (Blizzaks aren’t on yet) to bring the goods haha. Road went from snowcovered over wet pavement to snowcovered over frozen near the top.

To add, when I was outside it looked like snow is starting to mix in here in Altoona. Not home currently, but weather station at home is down to 35.

511 cams in the Laurels (US 219/22/30) showing the accumulating snow is underway up there.

It’s been a pretty rough run of it in the NYC metro. I believe they’re up to 665ish days since Central Park has recorded at least an inch of snow, which is far and away an all time record of futility there. Speaking of such records, this ought to throw some gasoline on the great MDT T debate haha. Saw this noted in CTP disco yesterday. There’s a half decent chance they’re probably not going to get to pass #2 though.. unless the Monday ob is taken on the tarmac behind a jet warming up for takeoff.

Timing/evolution for the precip changeover of tomorrow/Monday’s system continues to be a bit intriguing . I still think the Laurel’s/central have the best chance of seeing accumulating snows overnight Sunday after the transition. Further east into the Sus Valley I’m not as sure. I think everyone will see a transition before the precip ends but whether it’s something meaningful is the big question. We’ve all seen the overmodeled snow totals not come to fruition in the Sus Valley from similar set ups to this many times. One disadvantage I see is the cold air mass coming behind the front is certainly cold enough, but not impressively so. Surface temps look to be a bit of an issue that would likely mean a snow event that is a good bit less than 10:1.. especially in lower elevations. On the other hand, one advantage this system looks to have is dynamics, as it’s a pretty feisty shortwave having already caused (and is causing currently ) severe issues in the Ohio Valley and Deep South. We get a negatively tilted orientation of the trough as we develop a coastal low that runs up the frontal boundary. High res guidance like the NAM deepen the low pretty significantly as it comes up the Mid-Atlantic coastline. The dynamic nature of the system is why I think we get the changeover to carry across from the central counties to the LSV but accums are going to have to come from heavy rates with the marginal surface temps. Short range stuff like the HRRR starting to get into more decent range take accumulating snows into the Sus Valley fairly easily and the 18z NAM took it all the way inside I-95 from DC to NYC. The short term high res guidance also seem to have a bit of a lull in precip, shutting off in the central and lightening in the east for a few hours in the late afternoon/early evening. Rates then ramp up as precip shield redevelops and enhances with the deepening coastal low and that’s when the transistion starts to push east. Positioning of the frontal boundary coupled with the timing of the coastal running up it is going to be key for setting up the corridor of the best potential for accumulating snows.

Kuchera indicates the event is <10:1 in PA east of the Alleghenies ( central counties and LSV), a probable outcome given the changover scenario the Euro presents. A rapid temp drop in the column post front that allows a quick change to snow BUT the best precip ends before much colder air aloft arrives that would boost snow growth/ratios. Surface temps also fall from the 50s to near or just below freezing during the event (marginal but sufficient to accumulate with higher precip rates).

Euro is definitely much more pronounced with the vigorous shortwave and deeper with the surface low that runs the frontal boundary and enhances the the precipitation shield in C-PA post frontal passage. Modeling has been pretty persistent on some kind of an attempted changeover across at least some of PA the last several runs having this system with a sharp cold frontal passage. I think this scenario probably favors laurels and central counties more but the Euro solution does show how it could snow for most in here. The low develops along the boundary in VA and moves into central NJ (996mb at that point). GFS is trying to do the same thing but just isn’t as amplified as the Euro. Definitely intriguing, the range for this system isn’t really super far out (~D5).

Some occasional flurries/light snow here as well. PBZ radar indicates a wave of steadier snow that looks to get into the Laurels and perhaps some of the central counties as the afternoon wears on.

There’s definitely an opportunity to be had for the system progged near mid week next week. Coming on the heels of the stronger Sun/Mon system that resets the cold for a few days and a pretty decent -NAO block, there’s a good chance this northern branch feature is forced to track it’s low below PA.. which is a good start to getting any kind of meaningful flakes beyond western PA and the Laurels into the Sus Valley when it comes to clippers/clipper-like systems. Most modeling and ensembles have this feature, so strength and track of the feature are going to be the big thing. Today’s 12z GFS version is definitely more ideal, having a more defined and stronger surface low that tracks under PA which yields a better snow swath. A weaker feature going south of PA would still have some of the same issues with precip surviving east of the Alleghenies. A stronger one like the 12z GFS would establish some Atlantic fetch with the low hitting the coast, maintaining a swath into the Sus Valley and/or points south of there.

I’m not home currently but clearly the first measurable fell at the house this morning.

I probably slept through any pingers that may have fallen first thing this morning, but I may not have gotten any at all. Temp briefly was around freezing before midnight and hovered there til about 2am when a pretty good southerly breeze mixed down and kept temps in the mid 30s through precip arrival with no drop. Still a raw 35ºF with moderate rain. Wind shift and temp change highlighted (approx 140am) So now the race is on to see how big of a much needed rain event we get today. Most modeling has things in the 1.5-2” range in Central/Sus Valley for this event today/tonight.

Advisories were issued earlier this morning in the Laurels counties for mix/glaze of freezing rain (up to a tenth ice in the adjacent western MD counties). A larger portion of C-PA (likely the AOO-UNV-IPT corridor into NE PA) probably sees an initial period of wintry mix when the main precip arrives tomorrow morning given a pretty strong, though retreating high pressure over New England providing a CAD setup. High res guidance like the HRRR and that newer Rapid Refresh (RRFS) are more robust in cooling the 850mb layer on precip arrival and showing more frozen p-type (sleet and even snow). 3k NAM does show a bit of the same with regards to 850mb but shows freezing rain as a more dominant mix type. Reality is probably somewhere in between, with a better chance of a longer period of frozen the further north into PA one goes and biggest ZR impacts on the Laurel’s ridges and some of the adjacent ridges in the middle of the state. Could be interesting to see if advisories end up being warranted a bit further into the central counties. As noted by CTP, surface and road temps are likely to be quite marginal for impacts. A period of heavier mixed (esp sleet) could change that a bit.

Same down here. A bit more on the roofs, decks, car tops, etc than the grass which has a light dusting. First deck pic of the season haha

It’s been awhile since I’ve gotten a post on here… summer and fall are usually pretty busy for me. But I’ll be getting back to posting more regularly again. Certainly can’t miss possibly having some first flakes to observe overnight. Been watching the band of precip in western PA getting closer. It’s mostly clear currently and temp/dewpoint has fallen back to 32/29ºF.

Good bit of discrete cellular stuff firing from the ridge and valley eastward in the corridor of PA where the sun really came out this afternoon. Parameters (bulk shear/BRN) are very favorable for such things in all of C-PA today. Helicity values aren’t super noteworthy but they aren’t zero either, and that coupled with the best CAPEs being right up the whole Sus Valley currently means an area of 1-2 EHI values. Spin-ups are definitely possible just about anywhere. Tornado warnings now in northern Lycoming with a pair of decent looking couplets on BGM radar. The cell previously responsible for the tor warning in State College still looks pretty strong as it heads toward Sunbury. Everything severe is on the table today (esp severe wind) but I think the tornado/hail threat probably maximizes with the discrete stuff developing up front. This likely switches to a more clustered and/or linear type deal as we get into the late afternoon/ early evening and all those storms traversing WV/western MD and the Pa southern tier push into the Sus Valley. Of particular note there is the solidifying line from Bedford/Fulton south into MD/WV.