MillvilleWx

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

Once the low surface low reflection showed to be at the mouth of the bay, it was destined to have mixing issues further inland as the 925/850mb winds would throw the warmer air back further towards I-81. The Euro is actually similar to the GFS at 5H with just different SLP placements once we get to the slot near ORF. Models being jumpy right there mean they are struggling to identify where the primary surface low will be located as there is a distinct double barrel look now on all guidance, something I pointed out last night. Until that gets figured out, it'll be doing some moving and shaking with regards to the warm boundary layer intrusion. The CAD on the model is actually very solid leading in, and is actually the strongest surface ridge extension of all guidance. That's also another reason why the warm air made it so far west. The 1038 HP over Canada in tandem with a more tucked SLP at the mouth of the Chesapeake created a strong u-vector component to the wind field, forcing the easterlies to protrude as far west as I-81. It does correct and things improve with 3 hrs time, so it's not unreasonable to say that can easily shift back. In either case, that area of Rt15 on west is still the ground zero for this storm, IMO. I-95 to Rt15 will likely mix for a time with the further east areas mixing the longest. The deformation axis is still epic, so the back end love will be higher ratio love and can pile up quick. I still think the jack lies from WV Panhandle to the Catoctins up to HBG in PA. Northern Carroll/Balt Co into SoPA will also have the outside chance at the jack pending the overall evolution of the deformation band that is bound to establish itself. Like I said before, this is not totally figured out in the synoptic scale, so expect some movement here and there.

Well, the 00z runs were pretty much a great run for all of the sub-forum, and being totally serious, the CMC actually had some room for improvement (Yes, it could've been a whole lot better) and the GFS finally got a grip and has a surface reflection more indicative to its 5H progression. There wasn't much of a shift at 5H outside the eventual close off over DE, but that's something that won't be solved until closer to game time. CAD sig on both the CMC and GFS were classic for a precursor to a major snow for the Balt/DC megalopolis with the wedge down to SC/N GA. One of the biggest differences between the GFS and CMC was actually the extension of dry air at 7H that lead to the storm cutting off a bit abruptly. The 700mb moisture field was actually a good 1 deviation drier than the GFS as a whole, which would limit some of the total moisture content available for the storm. The + Theta-E advection nose was focused well to the north of the area on the CMC where all other models have it right into the sub-forum. One of the biggest reasonings was the CMC actually led an open 7H depiction until just north of our latitude, so that would cause the heaviest plume to be centered over NJ/NY/PA instead of MD/VA. I'm not too worried about that unless it's a pattern the other models pick up. In any case, both would provide warning criteria snows for much of the area. The deformation axis on the GFS is sublime with a co-located 7H and 85H frontogen placed along I-95 with 7H extension back to the western folks. There's a classic "warm nose" indication at 850mb that we see with bombing cyclones in these parts, and that's actually a good thing because that's an indicator of prime moisture advection into the boundary layer in co-location with the lift. This will be a fun event for many and we haven't even talked about banding yet. Good times

I told y'all not to worry

What day is it? Ugh Mids suck Anyway, quick thoughts on 18z: I didn’t see any appreciable changes with regards to the overall setup. GFS is jumpy right now and is on the most extreme envelope of western solutions at this point. The post early from Tomer Burg showing the 5H progs compared to ensemble mean says a lot. I think that might’ve been the most westward extent of the theta-E advection we could get in this setup. CAD still looks good. EPS is actually fairly solid with LP centers within a reasonable envelope favoring the same areas I mentioned before. Rt15 on west is sitting very pretty. I-95 and east will likely see a ptype shift during storm height before the Deform pivots through as the storm moves NE. The northern tier into PA will see it the longest. Don’t live and die by a model run y’all! Everything seems a go. 00z will ultimately shed more light, but don’t expect until Monday until the Synoptic details are more a bit more concrete. Then it’s meso time and banding. Talk to y’all later on the graveyard. Pass the Caffeine .

Night crew check in after 6 hrs of sleep (Will be heading back to bed shortly) Few thoughts gazing through things: 1. Initial thoughts holding with regards to ptype and where the best spots look to be. Fall line and west should remain majority snow unless we see a more amplified surface reflection. EPS showed more mixing out to even I-81, but if you look closely at the low clusters, everything that was inland was sub 990 with some at the low to mid 980’s. Remember the ptype algorithm is a smoothed mean that takes into account ALL members of the ensemble package. Even a few over amped members can skew the mean warm and could correct later in time as we get closer and filters the noise. 2. The confluence signature is becoming a positive feedback here with a classically aligned height pattern to our north that will pay dividends. High pressure over Quebec is consistently modeled around 1036-1038, which is solid for a snow event west of the fall line, so long as the low doesn’t over amplify. 3. Snow maps are fun, but best to look at QPF charts and base soundings. One of the bog things to look for in this storm is the CCB action on the final half of the system. Primary 8-10:1 caveats aside for areas along and west of the fall line for the first half of the storm, but this will have 15-20:1 potential within the deformation axis as 7H frontogenic progs have been off the charts across central MD, NoVa, Panhandle WV, into SoPA. There will be a nose of + theta-E advection when this begins to wrap as it crosses OCMD latitude. Where that points will be key in determining who gets the love on the back half. Even so, it’ll slowly gain latitude and sweep through to the east, so the ending of the system could be epic for many. It’s very classic in a Mid Atlantic MECS. 4. All that said, the typical Rt15 on west crew is in the best shape with elevated areas along Pars Ridge to Mappy sitting in a solid area due to elevation and mesoscale tendencies with bombing surface reflections. The lack of dry NW winds on the back half of the storm signify an expansive qpf shield is likely with this event, so even out to the mountains should see some love. Hancock on east is the best areas with some upslope component likely out near Garrett. 5. Sleet will undoubtedly occur for areas in the Blue Ridge in VA once south of Front Royal, but they could get smacked before a change over as southerlies scream out with the low reflection moving north. 6. Anyone who knows their climo should weight it in the result. You know your tendencies and nothing in this storm suggests a sway from the norm. A stronger high around 1040 would be what causes the mentality to shift, but it’ll likely fall short. Now if you’ll excuse me, I’m gonna go back to sleep and I’ll be back on the night shift tonight to add more tired thoughts to this event. Be happy y’all. There’s a storm brewing! .