Newman

Ticked colder, so did the 06z Ukie with heights lower/confluence stronger over southern Canada.

GEFS and GFS are near mint perfect, which has me nervous because they're always cooler and more progressive. We're going to see some crazy QPF bombs with our CAMs in the next few days.

If the current evolution holds, there will definitely be a dry slot that quickly shuts off precip. Euro has it coming in almost immediately behind the initial thump.

All the caveats apply to the long range NAM, but it's got the sleet line up to the M/D line by 18z Sunday at hour 84 and quickly moving north. Much more significant CAD at 850 keeping things colder in that layer, but 700s above freezing. Still though, all of SE PA already has 0.7-0.9" QPF before any flip to sleet. Places further north would thump for much longer, the coastal transfer was occurring

Places NW of the mix line are still 100% in play to see totals near 15-18in, and that could easily set up still across the Lehigh Valley or even just NW of I-95. Even if this thing continues to trend towards a glorified SWFE, some places could grab 12" in just 4-6 hours if the models are correct. There was a SWFE quite a few years back (don't remember which one) where Berks grabbed 8-10" in 4-5 hours. Just extend the duration on this one.

Starting to get concerned about the way this is evolving, but would love to get through the next 0z and 12z runs to hopefully tick back south. There's no breathing room anymore for I-95 and Philly crew, and teetering on the edge for Lehigh Valley. No reason anyone should cliff jump yet though, we haven't even gotten into the NAM range

What I'm really interested in monitoring in modeling over the next couple days, outside of the typical synoptic features: 1. How does the heavy WAA banding translate northeastward towards SE PA? Does it weaken as the primary dies off and the coastal transfer occurs, or does it plow through the area with vigor? 2. Where do our DGZ layers (could be more than one) set up and do we have any deep omega through these layers? Even if the surface is frigid, poor snow growth could still occur if the omega and DGZ do not align. 3. Where the 700mb FGEN band sets up on models, because IRL it almost always ends up further north

GFS is a great run, longer duration too as you leave a bit of energy trailing. You get the southern energy to ride up along the baroclinic zone with PVA pointed across the region, and then the central Plains trough swings through. 24-30 hour event for many. A widespread 12-20" from DC to Boston hasn't happened in quite some time.

100%. Let's just keep it here and snag an upper echelon MECS board wide.

The 6z Euro backed off just a tad with how far the primary drives north which kept the mid-level warmth south of Philly for now and also keeps the dry slot a bit more muted as the low transfers to the coast

Just got the chance to look at the 0z suite... Wow, there's your north trend and then some. Now that it seems increasingly possible you aim the intense WAA snows over the region, the entire evolution and storm is a bit different. I know the global models are showing a solid 18-24 hour storm, but from experience you usually only get 12-15 hours at most from a WAA thump until you dry slot. If I were to be super picky and extra HECS hunter, that would be what I'm not a fan of. But hey, if the Euro is right and you throw 1.25" QPF into an air mass with surface temps in the upper single digits and lower teens, as well with localized 700 fgen, easily crank out a few hours of 2-3+ in/hr rates. Also, this could be an overreaction from the models with the shift north, we'll just have to see. But I do think if you want a true long duration event, you want to play the balance between getting into the WAA snows and the backside ULL/coastal that develops as the storm departs.

Y'all, just remember how these storms go. You will continue to see waffling of models for the next 4 days, but we're definitely reaching an inflection point where we raise the ceiling significantly for SE PA. EPS looks great, another huge tick north

GEFS another tick north, 0.6" QPF up to southern Berks and Lehigh. 0.7" into Philly.

EPS also bumped up quite a bit from what I saw. Widespread 6-8" across SE PA at 10:1. Ratios get you 8-12". I think most would sign up for that

Ukmet is a huge hit!

DGZ is -12C to -17C. For many across SE PA, the entire atmospheric column is between this up to like 600 or 500mb. Even down to the surface in many places. If you throw some strong omega into the mix, poor snow growth would be the least of my worries. You're right though, if things were colder than -17C then we'd be looking at less stellar dendrites

6z GFS Op and GEFS came north again, AIGFS is a southern outlier for now. With a potential phase that models seem to be heading towards, I think a southern slider solution becomes much less likely

Are you thinking about chasing this one or gonna stick it out in Philly? I guess it depends on where we end up with this in a few days...

Yep, the 6z Euro AIFS also came back north and heading in that direction. We'll see if it's real at 12z

I'm pretty sure the Euro is going for an overrunning to coastal scenario. Looks like a completely different look now with a closed trough over the central Plains. Full phase

Absolutely, this will be a frigid storm. Just wait until we get into range for our CAMs that can handle banding.

Ukie another big hit. A bit less amped from the insane 12z run, but still gets 1" QPF to Berks and Lehigh.

Although I wouldn't go too crazy with ratios, seeing super deep DGZs like this could easily net you a 15:1 average ratio through the storm. Some places would exceed 20:1 within banding.

1" QPF line right along I-95 south on the CMC 0.8-0.9" throughout SE PA. 9° in ABE at the peak of the storm, 13° verbatim in Philly.

There's the north jump on the GFS and the CMC about to lay down the hammer.