MillvilleWx

This makes sense because there was a slight tick west with the surface reflection, a bit stronger and 925mb winds were able to make it to the fall line. The fall line and east will very likely mix during this storm. Perhaps slightly beyond it too, but for how long, and then where is the deformation axis established, and is there a TROWAL. I've seen that feature now on most model runs. A lot of times in SoPA, so something to watch because it's not far away from the northern folks and that would give some crushing totals whoever gets under it.

Okay y'all. So, here are my thoughts with the 00z runs and why the trend towards a more tucked solution is becoming favored, but it's not going to be the end all for everyone when it comes to snow chances. So, looking at MSLP plots for each of the 3 major globals (ECMWF/GFS/CMC), the models are pretty much in lock step with each other until the storm begins to breach the latitude of Hatteras and that's where we see some separation from the CMC/Euro combo and the GFS. The GFS is the flattest solution as it's not as aggressive with the digging jet associated with the s/w trough located over the Mississippi valley. Height rises out ahead of the trough are more subdued, so the storm doesn't amplify to the degree of the CMC or Euro. Both the CMC/Euro combo are fairly similar in the depth of the trough and relevant height rises along the Atlantic seaboard. This allows for SLP genesis to gain latitude a bit more with a northerly movement before becoming caught up by the negatively tilted 5H trough progressing through the Tennessee Valley. The GFS is a more NNE trajectory with less amplification and slower strengthening due to the lower dynamic field played by the weaker 3H jet alignment. In turn, by Thursday at 00z, there is a sub 1000mb low on both the CMC and Euro tucked into the Delmarva coast where the GFS is a 1003 about 100 miles off ORF. I think we'll see a correction in the GFS with a more tucked solution, but perhaps not to the degree of the CMC/Euro tandem that have it basically onshore at Lewes in the same light. After 00z Thursday, the CMC is much more progressive with the 5H trough and actually motions to the NE prior to weakening with a due easterly motion. Euro becomes stacked right south of Cape May and then begins to pull eastward, leading the QPF shield to slowly wane from the sub and end by Thursday AM. CMC is a little more aggressive with ending the precip as it punches the dry conveyor overhead overnight due to it's NE movement away from the coast. A general compromise would be a slight backing from the Atlantic seaboard which would keep the 925/850mb easterlies from overtaking the boundary layer back towards the fall line. This would lead to less sleet/rain and more snow, albeit lower ratios due to the warm tongue that will still creep into the boundary layer. Now the dynamics side of the precip field. The first round of precip will come in from SW flow aloft bringing in moisture off the gulf with qpf field expansion due to exit region of the 3H jet pivoting north into the area. There's a fairly robust area of diffluence ahead of the negatively tilted trough moving into the Tennessee valley on Wednesday, so regional lift is maximized, which is pretty standard for setups like this. We know this precip typically arrives a little sooner than modeled, and the current dew point depressions leading in are not insane and should be overcome fairly quickly with wet bulbs near and below freezing for most of the sub-forum. Areas along and SE of I-95 will likely be a touch on the warm side, but upper levels are still supportive of snow for a time west of the bay, so there will be flakes flying, at first. MSLP will develop along the SC coast and motion to the north, allowing for increasing low level dynamics to take shape with SFC and 850mb frontogen increasing in intensity as it gains latitude. Low level easterlies on the northern edge of the emerging surface low will begin throwing more Atlantic moisture into the mix as the WCB is fully established at + Theta-E advection noses along the Atlantic coast into the mouth of the Chesapeake. At this point, the 7H trough will be pivoting eastward with increased mid-level forcing focused over the Mid-Atlantic, allowing for increased banding potential over NoVA and Central-Western MD. Right now, current frontogen placement has the best mid-level ascent focused over the I-81 corridor over into central MD where areas of heavy precip will likely develop with embedded banding structures becoming more pronounced. By 00z Thursday, a classic pivot of the precip field will become recognized as the 5H trough axis begins to close off overhead and the added torque in the upper jet will take the SLP and draw it closer to the coast. This is obviously subject to some fluctuations pending the total evolution of the 500mb trough, but it's looking more likely with ensemble guidance indicating a bit more "tucked" solution, which the NAM12km (Yeah, I hate it) has as well. I don't see it being that amplified however, so the bias of the NAM is likely being shown and should draw away from the inland runner solution. In any case, as the 7H trough moves overhead, models show the trough closing off over the Delmarva which would lead to enhancement of the 700mb frontogenesis field with a more defined deformation axis becoming established. There's some indications of a TROWAL developing on some guidance as the 7H Theta-E analysis begins to take the classic "S" shape on the NW focus of the surface reflection, and is in conjunction with the closed 7H reflection. Pending the extension of the S curve will be where there's potential for a region of enhanced precip within the heart, or just north along the strongest 700mb frontogenesis. This is something to never overlook when it comes to heavy precip potential, and is generally a good indication of where the heaviest rates will occur within the developed CCB. On the Euro, there's excellent lift in two regions; the first is along I-81 where the strongest mid-level fronto is positioned. There's also a secondary precip enhancement near I-95 where 850mb frontogenesis is at it's max. Looking at 850mb temps, you can see the crash between 21-00z on the run when areas of CMD see temps in the lower boundary layer fall from +1-2 to -3-5C in a few hrs. That the CAA pattern typically associated with maturing cyclones on the west side of the SLP due to CCB as air cools considerably due to the deformation element. This will lead to a secondary banding structure that can lay down a solid amount of snow in time, and that's what the Euro has for our northern tier east of Carroll on this current 00z run. The CMC is a bit more drawn as the TROWAL is located a bit further north and intersects the incredibly strong 7H frontogenesis that is present over PA, extending into the northern portions of the sub-forum. The TROWAL is more pronounced than on the Euro, and is maxed over York County into the Coal country of eastern PA. That's why the clown maps show insane totals for that general region. The Euro shows the best axis of heavy snow out towards 81 with secondary max displaced to the east over Pars Ridge as they get in on the 85H frontgen band and rip for several hrs before the storm pulls away. General QPF distribution is similar for all guidance, but the Euro and Canadian show distinct maxes intersecting the areas where lift is maximized, as well as where the WCB pushes ashore along the Delmarva coast. PWATs are well above normal with Euro coming in between 1.5-2.5 StD above normal on Wednesday and Wednesday night with up to 3 StD where the deformation axis is located, so the precip potential is absolutely there to breach 1.5" with local 2" spots possible within the best areas of lift. Bringing this all together, I think we're beginning to see where the max potential will be realized for the sub-forum, and the storm overall. The Blue Ridge from Front Royal on north along I-81 over into south-central PA will likely be ground zero with a relative axis of heaviest snowfall extending east into the Catoctins, Northern Carroll, and perhaps northern Balt county, pending the deformation extension to the east. 10-16" of snow with local 20"+ totals will be realized in parts of the sub with incremental decreases further east from the line I mentioned. The urban corridors will likely mix and end up either high end Advisory or low end Warning criteria snowfall. Pars Ridge will have a secondary max of 8-14" with potential for more pending localized banding structures. I'll have a final call Tuesday night into early Wednesday.

Truth. I'm gonna be working on it in the next 2-4 years. Then you'll be stuck with me

Correct. It's further south than the CMC, so the deformation axis gets into the sub-forum. It's a good middle ground between the CMC and the GFS really.

Guys, I'll have a more in-depth post about the 00z runs tonight and I'll lay out what I saw with regards to everything. There were many in the sub that got smoked by the Euro and some will be hanging on for dear life (I-95 brethren). The fall line will be a major play with this one. The further away, the better. It's a classic setup for these parts. You know your climo. Temper expectations.

You mix for a time, then you be whacked really good by a band that develops along the 85H frontogenic placement. 850mb temps crash from ~+1C to -5C in 3 hrs and it rips for like 6 hrs before shutting off.

No discernible differences so far between the globals in SLP. Will keep posted. Been digging more using AWIPS. FINALLY a quiet night here after todays ridiculous wind event

Yeah, we don't even look at the UKMET for any reason down here. Our order of prevalence is: 1. Euro/GFS 2. RAP/HRRR for meso 3. Nam Nest 4. Canadian 5. Hieroglyphics 6. Crystal Ball 7. Icon 8. That's So Raven telekinesis 9. A straight up guess out of a hat 10. Nam 12km

It's def closer in the SLP track, but still not as amped. Agreed. GFS was a bit flat comparing. Probably just GFS being GFS

That mega band in SoPA is the TROWAL I've been mentioning. Absolute classic and can confirm when I look at the 7H Theta-E's

Haven't gotten a good look at the GFS yet since I am still getting ready to head out for work. The thermal profile on the GFS is always a miss with these events and likely not cold enough in the beginning stages of the storm. I think the surface and lowest reaches of the boundary layer trends colder if the HP over Quebec continues to signal 1037-1039 strength. The height pattern out over the eastern CONUS leading in isn't something extraordinary that would mute some of the surface cold. The 7H prog here is basically the only "concern" I see if this would deflect the strongest mid-level frontgen towards NJ/DE with TROWAL potential locked over the NE portion of the sub, at best. Would like to see that low set along the coast ala the Euro to get a deformation pivot over the CMD/SoPA. Overall, it wasn't bad really. Did tick back in the extremes some, but the synoptic details are still not squared and there's room for improvement. And as always, meso hasn't even been taken into account yet. I wouldn't sweat it if anyone is "worried", except Ji cuz then he would be out of character.

The Nam12km is meh with regards to handling synoptic, but the Nam Nest is actually fairly decent inside 36 hrs. It nailed the March 2017 sleet disaster when everything else was barking all snow. I’d start looking at that for 00z tomorrow night. Now for the varsity synoptic models .

I am way too tired to look at stuff right now in-depth, but there isn’t much change to my previous thoughts. I may slightly move areas like Northern Carroll/Balt/Harford Counties into a more favorable position to Max potential with the system. There will likely be two monster bands that setup during this event once the trough goes negative and closes off somewhere over the Mid Atlantic. There’s been a history of the -2 and -9C isotherm at 7H having distinct bands develop within intense cyclogenesis and was very apparent in 2016 with Baltimore to Philly clocked by the -2 and I-81 with the -9. Someone I know did some research and a paper on it, so I’ll have to look more into it. In either case, deformation is where higher ratio fluff will pump totals rapidly for whoever gets them. I wouldn’t waste time on the NAM beyond Monday right now. ICON is not a model I’d put much stock in. Focus on UL progression at 5H on the GFS/CMC/ECMWF, the track of the 7H low, and frontogenic placement during Wed afternoon and evening. Also, follow the finger of + Theta-E advection. Where that points will be where the WCB and CCB meet to help form the deformation axis. There could be a sneaky TROWAL in the mix too for our NE areas that could provide an E-W enhancement for snow. The Euro was showing a little flavor of that on its run across SePA. I’m gonna watch GFS come in, but I may also fall back asleep. I’ll catch y’all tonight regardless. Fingers crossed for HH .

It was gonna be epic. No doubt. 5H was pure weather porn

Euro made a 25-30 mile tick to the SE with the progression of the SLP and can be seen looking closely at 925mb and 850mb with the winds and it showed with the depth and extension west of the warmer air within the boundary layer. This was actually a step in the right direction. Also, I think the CAD is underdone considering the surface setup with the HP positioning over Quebec City and a strength of 1038mb. Thicknesses reflected were in line with GFS despite being more robust in the surface reflection. I think this will trend more favorable in the short term. Question is the tuck of the SLP once it gets to ORF. If it stays even 50 miles off the coast, we are looking at an epic run for many. The western crew and northern crew would undoubtedly get obliterated with that run. Absolutely no question.

I need to get myself back east because this is literally everything I've been mentioning. There will come a time

Meanwhile, Ji is running low on Valium

Oh btw, there's a chance at thundersnow in this storm. Just wanted to throw that tidbit out there looking at regional soundings. Slight tilt back with weak elevated CAPE sig within the deformation axis as the storm cranks off OCMD. So....yeah

The issue is the shallow layer between 850-750 that has a warm nose near the 0C isotherm, so pending the site and algorithm based, one will have ice/sleet and other will have snow. With intense lift within the low to mid boundary layer, I'd lean snow with that look. Lighter rates would switch to a mix. Banding will be prominent with this setup. People here need to not sleep on this setup when it comes to meso. This is how you get your 2-3"/hr snowfalls. 7H and 85H frontogen with this setup is silly. Someone in the Mid Atlantic is gonna get absolutely destroyed, and it won't be till gameday till we know who...... we all know who

The 850-700mb frontogen on the 06z GFS is otherworldly. Whoever stays all snow with this system is gonna shovel well over 12". Mark my words. Crazy aviation shift over here this evening, so bare with me.

I'm glad I'm in agreement with LWX. This system will not be moisture starved, that's for sure. How far west can that boundary layer warmth protrude into the region, and then when does it shift back for those that mix. 6-8" of snow with 1" of sleet is on the table along with areas that see 12-18" of snow with local to 22". All on the table with this setup.

I know it's the NAM, but keeping an eye on the Monday storm progression. I took a look through 42hr and the NAM is almost lock-step with the CMC in the evolution at 5H and the SLP movement and strength. The GFS was way stronger and the Euro was much weaker. The CMC is the compromise right now, so I'm curious to see what the NAM shows the rest of the run (Yes, it's at range, but it's something to compare with what we have. Not taking as gospel. Just for reference).

Good catch. I remember seeing on the Euro early on there was a bit of a difference in the strength of the surface reflection on Monday compared to other guidance, so that makes sense that it would provide a slight negative feedback. We're getting down to the nitty gritty on the synoptic scale, so that piece on Monday will be important to resolve before we have a distinct idea on what to expect with the SLP positioning on Wednesday. @MN Transplant said it best earlier with regards to the SLP track. Thanks for the trend gif Grit

For sure. That's one of the reasons I see mixing even back as far as Frederick as a possibility with this one. "How long?", is the question. Still a fair amount of QPF to work with and the meso aspects are far from settled. Hopefully the low can find a medium and hug the coast and not reside over the coastal plain. Someone will get rocked from this in the sub-forum and my bet is the 81 corridor right now.

No studying over here! My school days are long gone. Working the mid shift tonight and have Aviation grids tonight. Will be easy shift for me as the day shift gets the screaming northerlies later today