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WxUSAF

January 12-14, 2019 Storm Discussion STORM MODE

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This is the comparison between 6z gfs and 6z euro. Euro hangs a ton of energy back which just flattens the flow combined with the stronger tpv streamer which also compresses hgts. Gfs bundles the energy better at the base of the trough, combined with weaker tpv streamer (though trended a bit stronger at 6z from 0z) allow hgts to bend back towards the coast allowing for a closer coastal pass. 

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36 minutes ago, showmethesnow said:

But the weaker and progressive flow is in response to the NS. Weaker because the NS is not giving the storm room to amplify and more progressive because we see very little height rises in front of it to slow the flow.

I think a piece of this puzzle that isn't being talked about enough is the upstream issues also.  The pattern is changing but has not transitioned fully yet and the fast pac jet is still pressing into the west coast and pushing that ridge east.  As that happens its compressing the trough and forcing it to elongate and flatten between the ridge from the west and the NS blocking it to the northeast.  That might be causing just as much of the problem as the NS over New England.  Get that to back off and allow the trough to dig more and amplify and it might rise the heights enough to offset that NS problem for us.  But the trough is de amplifying and so the NS is going to win that muscle match.  

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@tombo82685 interesting that it seems the EPS has been consistently more bullish than the Op for the last 48 hours or so (that's probably not perfectly correct, but seems to be true enough).  As I said yesterday, I'm still *barely* good with that, but we're rapidly approaching the time window where I'm worried that the Op would be handling subtle features better than the ensembles.  Hope 12z Euro matches that 6z EPS mean. 

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30 minutes ago, MillvilleWx said:

Models are beginning to hone in on the median ground for the setup. The trimming on the northern side is occurring because of the confluence and dry mid-level northwesterly flow north of our area. It’ll probably be a sharp gradient of nothing to accumulating snow across PA. I still see our northern reaches getting in on the action and secondary band like structure right on the edge of the confluent zone where mid and low level convergence sets up. Pinning that will be something that gets settled closer to game time.

As for rest of forum, increasing likelihood of Advisory level snows with 1-3/2-4 inches from I-70 corridor to NoVa and 3-6” within the area that’s gets a cross of the best WAA snows and the redeveloping coastal. That part still has yet to be solved, so those numbers could bump if we get a trend towards a better NW expansion of precip field when the secondary takes shape. The max snowfall I could see from this is 6-8” with the Central Shenandoah the prime spot due to better position within the left exit region of the southern jet streak and aided orographic enhancement, maxing out on lift within the DGZ.

So far, what I mentioned yesterday and what LWX has in their discussion lineup, so I don’t feel the need to change my forecast right now. I still wouldn’t rule out a dual “max” and someone along Parr’s Ridge getting 3-5” of cold smoke due to that convergence zone along the confluent setup to the north along with aided orographic enhancement. Ratios from storm will range from 8:1 within very light snowfall where needle type crystal structures the common snowfall type to 15-20:1 where best lift/omega resides within the DGZ on both the jet streak and orographic enhancement, as well as the deformation axis on the northwest flank of the secondary. That latter part will probably take another day or two to be solved.

Just bringing this over from the old thread.

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12 minutes ago, psuhoffman said:

I think a piece of this puzzle that isn't being talked about enough is the upstream issues also.  The pattern is changing but has not transitioned fully yet and the fast pac jet is still pressing into the west coast and pushing that ridge east.  As that happens its compressing the trough and forcing it to elongate and flatten between the ridge from the west and the NS blocking it to the northeast.  That might be causing just as much of the problem as the NS over New England.  Get that to back off and allow the trough to dig more and amplify and it might rise the heights enough to offset that NS problem for us.  But the trough is de amplifying and so the NS is going to win that muscle match.  

I am not so sure that is a fixable problem though. At least I believe we are much more likely to see the changes we need with the NS as opposed to the flow coming from upstream. So I am been pretty much focusing on that.

Shame I will be very limited if not checking out for the most part for the next week while I am in Vegas. Between this storm now, which has more promise then I expected and with what looks to be a very active and promising extended range I would have really enjoyed the tracking. But I guess booze, gambling and buffets come first. :lol:

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6 minutes ago, WxUSAF said:

@tombo82685 interesting that it seems the EPS has been consistently more bullish than the Op for the last 48 hours or so (that's probably not perfectly correct, but seems to be true enough).  As I said yesterday, I'm still *barely* good with that, but we're rapidly approaching the time window where I'm worried that the Op would be handling subtle features better than the ensembles.  Hope 12z Euro matches that 6z EPS mean. 

I think you guys are good for 2-4 at the very least IMO. What you also have to consider is, the coastal impact is still 3.5-4 days away about a day later than the overunning setup. These Canadian impulses are fickle, any sort of changing of the handling of the tpv and pieces of energy rotating around in regards to speed and strength can make for a big difference downstream. 

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Just now, tombo82685 said:

I think you guys are good for 2-4 at the very least IMO. What you also have to consider is, the coastal impact is still 3.5-4 days away about a day later than the overunning setup. So you have basically 3.5-4 days still for that. These Canadian impulses are fickle, any sort of changing of the handling of the tpv and pieces of energy rotating around in regards to speed and strength can make for a big difference downstream. 

Yeah, true enough.  I'd rather go back to where the Euro had a widespread 3-5" for us, almost entirely from the WAA snows.  Less complicated.  More boom/bust potential when you throw in the coastal as @psuhoffman has said.  WAA snow extent also seems like it might have a modestly narrow N-S extent.  Still some wrinkles to iron out.  I like 2-4" for NOVA/DC/MD as well for now all things considered.  

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1 minute ago, WxUSAF said:

Yeah, true enough.  I'd rather go back to where the Euro had a widespread 3-5" for us, almost entirely from the WAA snows.  Less complicated.  More boom/bust potential when you throw in the coastal as @psuhoffman has said.  WAA snow extent also seems like it might have a modestly narrow N-S extent.  Still some wrinkles to iron out.  I like 2-4" for NOVA/DC/MD as well for now all things considered.  

Yup, you're basically trading in one for the other possibly. The models this morning seem to be timing the strongest push of confluence with overunning snows thus drier look there at least from m/d line north. They then move that tpv streamer out a bit faster allowing hgts to recover for possible coastal impacts. I would still like to see better bundling of energy at base of the trough on the euro. I don't like how it's so strung out. Also need to increase wave spacing between the tpv streamer and coastal to allow for even better hgt rises. At least in your case it's not like we are asking for a coastal shift of 500 miles. 100 miles north would make a big differences and still within realm of possibilities at 3.5-4 days

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Just hoping we don’t get caught between the initial energy phasing out and a coastal taking over. Would absolutely suck to be the dry area in between two swaths of snow. 

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1 minute ago, jayyy said:

Just hoping we don’t get caught between the initial energy phasing out and a coastal taking over. Would absolutely suck to be the dry area in between two swaths of snow. 

My concern as well. That low needs to phase (as always) south

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2 minutes ago, jayyy said:

Just hoping we don’t get caught between the initial energy phasing out and a coastal taking over. Would absolutely suck to be the dry area in between two swaths of snow. 

This.  Only the out of its range NAM shows this now but if you’re looking for a way to fail this is it.  Initial precip runs to the north and coastal never really gets going or stays too far south.  

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16 minutes ago, showmethesnow said:

I am not so sure that is a fixable problem though. At least I believe we are much more likely to see the changes we need with the NS as opposed to the flow coming from upstream. So I am been pretty much focusing on that.

Shame I will be very limited if not checking out for the most part for the next week while I am in Vegas. Between this storm now, which has more promise then I expected and with what looks to be a very active and promising extended range I would have really enjoyed the tracking. But I guess booze, gambling and buffets come first. :lol:

Have fun man... enjoy the break from life.  

I didn't mean to imply it was "fixable" just that it was a problem that wasn't getting much attention.  In the end it might be a bigger problem and probably not a fixable one.  But lets wait and see.  I can definitely say the longwave pattern is OK but that compression is less then idea...the question is does the system have enough amplitude and "just enough" space to sneak in there and get it done.  I can't possibly answer that.  It's close just looking at the progression.  I think if the system gets amplified enough in the Miss Valley and can survive somewhat intact through the compression effect to make the jump to the coast where it can then utilize the surface baroclinic boundary to reorganize it could have just enough room to get it done.  If it ejects as an elongated sheared out POS we are probably looking at a very low end event.  

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15 minutes ago, WxUSAF said:

Yeah, true enough.  I'd rather go back to where the Euro had a widespread 3-5" for us, almost entirely from the WAA snows.  Less complicated.  More boom/bust potential when you throw in the coastal as @psuhoffman has said.  WAA snow extent also seems like it might have a modestly narrow N-S extent.  Still some wrinkles to iron out.  I like 2-4" for NOVA/DC/MD as well for now all things considered.  

There are a lot more moving parts to this now then with the west to east WAA wave scenario we were looking at 48 hours ago.  Others seem to be catching on to my "fail scenario" where the initial WAA either rides to our north or gets shredded by the confluence and is weak sauce and then what's left of a weak strung out mess transfers to the coast but develops too late to help and we get stuck in between.  We have seen that play out before.  It's the threat of a total fail here.  Not saying that is where we are heading but its on the table with this setup vs the more stable WAA look we had before. 

Another concern I have with this situation as modeled now is regarding ratios.  People are assuming high ratios but to get good ratios we want to get into some decent lift.  If we get .25 qpf over 24 hours from periods of very light precip that is most likely not going to have high ratios.  I know some seem enamored with this long drawn out event but frankly I would rather get .25 qpf in a few hours then .25 qpf over 2 days.  First of all with precip that light, it wouldn't take much adjustment for that to be shredded by the confluence and then you go from .08 qpf in a 6 hour period that you were assuming would add up to an inch of snow to flurries.   You weaken the WAA band ahead of the stj system some and that becomes a nuisance snow event and then you adjust the northern fringe of the coastal south 20 miles and we miss that...and there you have the disaster scenario.  People are looking at the expance of qpf and thinking...were safe, when not so much.  

Putting the deb away, there is also an equal chance this all goes the other way.  Amp up the system just a tad, and that WAA banding could be a nice primer and then get that coastal to adjust north just another 30-40 miles and we end up with a 4-8" event region wide.  So I am not saying this is going to unravel just I can see how it could and some seem to be convincing themselves we are safe for at least an advisory event based on the expanse of light qpf surrounding our area.  

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16 minutes ago, tombo82685 said:

Yup, you're basically trading in one for the other possibly. The models this morning seem to be timing the strongest push of confluence with overunning snows thus drier look there at least from m/d line north. They then move that tpv streamer out a bit faster allowing hgts to recover for possible coastal impacts. I would still like to see better bundling of energy at base of the trough on the euro. I don't like how it's so strung out. Also need to increase wave spacing between the tpv streamer and coastal to allow for even better hgt rises. At least in your case it's not like we are asking for a coastal shift of 500 miles. 100 miles north would make a big differences and still within realm of possibilities at 3.5-4 days

As with most storms, this will probably inch north over the next 2-3 days.  That puts us in a good spot for a potential boom scenario if the coastal does play out.  The confluence can also serve to create a good band somewhere in the WAA snows as HM has been discussing on twitter recently.  But that can create a narrow gradient, particularly on the north side of that band from a healthy 2-3" to nothing.  Weaker gradient on the south side, but still noticeable.  Creates a scenario where our Jackpotville friends along the M/D line score big from the WAA snows while DC-Balt get ~1" spread out over a long duration and then we wait for the coastal to take over.  

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@psuhoffman I totally agree and you can see the divergence of those 2 boom/bust scenarios well in the ensembles.  Relatively few that split the difference sort of like the Euro Op is doing now.  GEFS has been leaning toward the boom scenario the last few runs and seems like GFS Op is going that way as well with the coastal getting us.  EPS also trending that way a bit at 6z it looks like.  

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3 minutes ago, WxUSAF said:

As with most storms, this will probably inch north over the next 2-3 days.  That puts us in a good spot for a potential boom scenario if the coastal does play out.  The confluence can also serve to create a good band somewhere in the WAA snows as HM has been discussing on twitter recently.  But that can create a narrow gradient, particularly on the north side of that band from a healthy 2-3" to nothing.  Weaker gradient on the south side, but still noticeable.  Creates a scenario where our Jackpotville friends along the M/D line score big from the WAA snows while DC-Balt get ~1" spread out over a long duration and then we wait for the coastal to take over.  

Yup, those WAA snows can certainly have an over performing snow band. Thats where your best shot of good ratios would be too as you would get better lift in the DGZ combined with cold air a loft.

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22 minutes ago, jayyy said:

Just hoping we don’t get caught between the initial energy phasing out and a coastal taking over. Would absolutely suck to be the dry area in between two swaths of snow. 

no doubt a possibility...especially up here.  If we put hopes in the solutions showing energy hanging back, its not much different in evolution than a run of the mill Miller B. We hope/wait for the transfer and stare at radar in hopes for westward expansion.  Im w/ USAF.  Just give me one juiced system and hope for a north trend.  Screw the follow up.

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21 minutes ago, WxUSAF said:

@psuhoffman I totally agree and you can see the divergence of those 2 boom/bust scenarios well in the ensembles.  Relatively few that split the difference sort of like the Euro Op is doing now.  GEFS has been leaning toward the boom scenario the last few runs and seems like GFS Op is going that way as well with the coastal getting us.  EPS also trending that way a bit at 6z it looks like.  

I guess it could go in between if we get a light initial wave and the fringes of a weak coast and adds up to a 2-4" event...but yea it might even be equally or more likely it falls one way or the other in the boom bust category.  If I had to guess I would lean boom here.  This is a pretty healthy system coming at us from the Missisippi Valley and the flow, while compressed isn't the worst shred factory I have ever seen.  The high isn't even that suppressive, in PD2 there was a 1040 high sitting over Montreal and that low took a similar track and was only about 1012 mb and that system got 1-2 feet of snow to Vermont.  I know the upper level flow was a lot more relaxed in that setup over the northeast BUT my point is get that flow to back off just a little, get this storm to hold together just a bit better and more amplified and there is no reason this can't adjust north 50 miles.  We don't need it to get snow to Vermont this time.  But if a weak sauce system can get snow to Vermont with a 1040 high over Montreal there is no reason this can't get some snow into our area with a 1040 high in about the same location.   I think there might be just enough space in the flow for a slightly more amplified solution here.  And we have had enough bad luck lately its just time for something to work in our favor.  I just wish my "fail scenarios" didn't come true as often as they do!

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Nam isnt going to run long enough not that it matters but after 84 snow would overspread the area. Vort held back this run as you can see. 

namconus_z500_vort_eus_53 (1).png

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NAM really dampens out at h5 but I wouldn't expect it to handle that feature well at range.  Still I would have thought it might be more amped than dampened at this range.  onward and upward.

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1 minute ago, Chris78 said:

Good thing the NAM stinks at range lol.

namconus_asnow_eus_28.png

Thats a perfect match of the winter to this point for my yard lol. Not sure I would have even looked at the NAM on my own at this range. At this point I am pretty laser focused on the EURO and GFS op runs.

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29 minutes ago, pasnownut said:

no doubt a possibility...especially up here.  If we put hopes in the solutions showing energy hanging back, its not much different in evolution than a run of the mill Miller B. We hope/wait for the transfer and stare at radar in hopes for westward expansion.  Im w/ USAF.  Just give me one juiced system and hope for a north trend.  Screw the follow up.

A southern system moving west to east that transfers from the TN valley to the coast is not a miller b.  I have seen that classified as an a/b hybrid since there is a fairly significant transfer and redevelopment involved but it's not the same category as a northern stream system diving in and then transferring energy to a developing coastal with little STJ involvement.   The hybrid types are actually some of our biggest snowstorms while the true northern stream miller b's are mostly a disaster scenario for anyone southwest of the Philly area.

I am not even sure I agree with some of the "hybrid" categorization.  Yea there is a jump and redevelopment of the surface system but that is really just mostly a function of the southern wave taking enough of a northerly track initially that it ends up running into the Apps and enough resistance to force a jump.  When the storm tracks along the gulf coast it can turn the corner unimpeded and you get some jump often...from southern GA to the SC/NC coast often...as it approaches the coastal baroclinic zone and leaps...but it's not as noticeable as the transfer from TN to the NC coast and without mountains there to interfere the redevelopment isn't as extreme.  

But its not the same interaction really as the pure miller b and often doesn't involve as complicated a phasing scenario.  Also...it usually is only an issue when the system is weak.  Yea when the initial TN valley system is falling apart and washing out it creates the illusion that we have the same problem as with a miller b where the coastal can form too late...but that is simply because the initial system was weakening and would have weakened and the precip would have been shredded by the mountains and done little for us even without the coastal development.  If you get a healthy amplifying system up into TN that then jumps to the coast...that is the setup for some of our biggest snowstorms (assuming there is a cold high in place).  We get the initial WAA thump, then with a healthy system transferring we will also get into the CCB of the developing coastal.  Or sometimes, like the January 2004 system, the coastal will get crushed by the flow and miss...but we still got 5-8" around here from the initial wave to our west so no one cared much.  The issue here is that the system is being compressed and washing out NOT the transfer and redevelopment.  

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