MAG5035

With model's seemingly starting to zero on taking the surface low essentially to the Chesapeake Bay Bridge (the Baltimore one), it's pretty likely at least the southern parts of York/Lancaster have a period mid storm where they mix. I think it'd be mainly sleet north of the mason-dixon line but a low track that close is probably going to introduce p-type issues there for a couple hours. Once the low starts to make it's fade heading toward going under Long Island and New England I think anyone mixing in PA will promptly go back to snow.

<3

In other important details about this incoming barn burner, it has been named Gail.. haha. https://weather.com/safety/winter/news/2020-12-14-winter-storm-gail-noreaster-east-coast-snowstorm

Crushed.. this gets everybody here and even gives the Pittsburgh folks warning snow. It does nose mixing (primarily sleet) up into York/Lancaster and even up towards Harrisburg mid-storm. Using 10:1. Kuchera totals are 2' + in the AOO-UNV-IPT corridor.

GFS has really looked solid the last full cycle back to 0z last night. It's also tucking the low from SE VA just inside Chesapeake Bay thru the Delmarva now like the Euro has been doing, which has been solidifying our northern and NW folks into the better totals and keeping the Pittsburgh/SW PA folks in high end advisory (maybe low end warning) numbers.

Hmm it's still showing some surface reflection into the OH Valley on the models, so I don't know if it'd be a clear cut miller A if we're being technical. But with the coastal getting going early and tracking where it needs to for this area on pretty much all models now.. it might as well be one.

A system originating from the Gulf states developing a coastal low tracking up the coastline near or on the Delmarva into the teeth of a strong Canadian high are what C-PA snowstorms are made of.

Lol, I was using the 12k NAM since some of this event is still outside 60hrs. 3k NAM is definitely NOT acting up haha, geesh.

Yea, my bad. it's starting to pull the heavy snow swath back towards where general consensus of the other guidance has it. Seriously though, did anyone else with WeatherBell have a screwed up 18z NAM like I did?

Well looking at it with Weatherbell's map something was up with the model run itself on there. Def the current 18z run but it there was some of the precip shield that cut out on a couple frames, really weird.. and it's not totaling snow right either. Heres what it did hr 57 vs hr 63 frames for example 57: 63 So there's definitely something up there, I know the TT maps can really exaggerate snow totals near the mix areas but it was like looking at a completely different model run lol.

Eh not really, track did shift SE a bit coming up the coast but still a lot of mix in the LSV and it really shut off the precip fast once the low's gettin by us.

Yea there were definitely elevated ratios there and in that general band of the LSV that saw those 30+ totals. Jan 2016 was a colder system but if you have a good snow column with no real warm nose in it (enough to affect the snowflake structure) and any typical surface temps cold enough for snow to accumulate well... the thing that matters more for ratios is where in the column the lift is occurring and what the temperatures are at that particular layer. For this, the better ratios will probably be where the best lift is at the 700mb level (and somewhat above) and where 850mb temps don't flirt with 0ºC.

Yea this is where we have to be careful. It's definitely possible with this event in terms of having a widespread area of 6"+ like that. Again the big question for this subforum in particular is not really whether all of us see decent snow totals but where the swath of heavy to excessive snow is, and how expansive... with the secondary question being how much if any mixing gets into York/Lancaster counties. I tend to think any swath of widespread 14-18"+ amounts may be more focused than the broad swath the Euro is presenting, with the majority of the rest of us NW to 2001kx in Clearfield in the 6-12" range. Models are still kind of up in the air about that. Canadian is still the tightest of the bunch and has the excessive snow swath only really in the LSV from H-burg and SE out to Allentown and really hurts the folks back this way in JST/AOO/UNV taking away the bigger event and beyond in western PA. Canadian ensemble has the swath somewhere in between the GEFS and Euro EPS though. NAM is way NW with the mixing line and heavy snow swath (probably too much so). GFS does okay, its starting to hug the coast a bit more but still has a more outside track on approach. Euro is pretty far inside, actually inside the Chesapeake Bay across the Delmarva to Delaware Bay with it's low on the way up the coast. It's actually pretty much what the NAM did track wise, except the NAM was much warmer thermally.

The more elevation dependent HRRR ended up being correct over the other ambitious guidance this morning. Probably could call it a T here, but nothing measurable fell. Looks like it stuck from about 1800’ or so up. Looking NE Good thing we might just scrounge up a bit of snow Wednesday lol. Did anyone actually see much this morning?

Steadier precip has arrived, looks like a rain/snow mix currently. 37ºF

Euro's hanging the deform max in between I-99 and I-81 this run, everyone in here's crushed.

So far I'm seeing the same general thing as last night. GFS most southeast with it's heaviest snow axis and limits NW extent on 6"+ and CMC simultaneously with good extent in the subforum but it's axis of downright excessive snows cutting from York/Lancaster counties to Allentown (a bit NW of the GFS heavy swath). The good thing for us is we're essentially boiled down to where the excessive snow (12-18+ type stuff) band is going to be within what should be a subforum wide warning event (I expect warning criteria for 2001kx and wsptwx too) and perhaps some mixing issues for a time mid-storm near the LSV MD border. You should see the discrepancy with the GFS/GEFS vs the other globals over in southern New England.

On tomorrow's event, been watching the HRRR. It's been having more p-type issues especially in the Lower Sus Valley but even in the south-central counties back near the I-99 corridor. Could end up being even more elevational. I know surface temps have dropped off in a few spots where it cleared a bit but mesoanalysis showing 925mb temps aloft lagging in the south and HRRR has trouble getting them to 0ºC in the LSV during the event tomorrow morning. Something to consider for this event in the short term.

Yea GFS has had real estate between the coastline and the low center. Most other guidance has had that low inside the Chesapeake and Delaware Bay before it starts the fade under LI. I tend to lean towards the inside guidance. SST's are on fire anomaly wise and our cold air mass, while plenty cold for this... is not overly frigid. Would suggest the boundary this runs on will be right along the coast.

A little early for Mt Holly to hoist watches IMO, esp on the other side of I-95. They better hope the NAM's not right lol. Tomorrow afternoon will probably be watch time for CTP once tomorrow's wave is mostly out of the way and the 12z suite is out.

Hopefully I'll get to worry about that Thursday lol.

No idea what to expect here out of tomorrow but I’d consider a quick 1-2” a win. Snowboard has been deployed in the yard. I handmade this thing out of some misc scrap wood around my shop room last winter and never got to use it.

Yea we do need to start addressing this thing tomorrow lol. I think there's more uncertainty with that than Wednesday's event, which could be problematic because the timing of this is right at morning rush tomorrow. That combined with being the season's first chance at widespread snow is likely why they're pulling trigger on advisories for a general 1-2" in the LSV counties. There could be a ribbon of snow that doubles up on that if some of these amped meso models have their way. CTP discussion references good lift in the DGZ, which will ramp ratios. Limiting factor at least in the initial stages of the precip arriving probably will be B-layer temps probably being a bit warm. Precip may start as rain in the LSV. If the rates are there, look out once stuff starts accumulating.

Early looks at the 12z Euro ensemble, I've used products that separate tomorrow's event out. 48hr snowfall mean 12z vs 6z: 24hr snowfall probability of >6" 24 hr snowfall probability of >12" No probs were generated on the >18" and >24". No matter though, that's about as strong of a significant snow signal as you'll get out of the ensemble guidance.

The setup is such that Pittsburgh would do well with a miller B type scenario. The problem is the Ohio Valley low isn't very strong and we're transferring to the coast pretty early, making the bulk of the precip shield associated mainly with the coastal low. You hold that Ohio Valley low just a bit longer and stronger and you can likely get a slightly better easterly fetch into western PA to the Ohio Valley and perhaps maintain a better precip shield across western PA. I don't think this region is in play for what's looking like a swath of excessive totals somewhere further east BUT I do think low end warning totals can be achieved if the more amplified solutions have their way. We'll need the meso models to get more into range to see if that idea has any legs. For now though, I have pretty decent confidence with Pittsburgh metro and surrounding seeing at least a decent higher end advisory event by the end of this. I think the GFS is just a bit too tight and SE with it's swath. 12z Euro coming in a tad SE with it's heavy swath and appeared a bit weaker on the Ohio Valley side of things (def NOT on the coastal end), but maintains the advisory totals over the area.