ORH_wxman Posted December 8, 2016 Share Posted December 8, 2016 Figured we should start this thread. I posted this map in the model thread, but I circled the key to guidance trending better...the split flow to the north is creating confluence downstream which builds out high pressure back northwest toward Quebec and not let it slide offshore. Still too early to get too specific, but model guidance has been converging on a significant snow event for at least a good chunk of New England....where ptype issues set up is still to be determined. GFS at 12z is the most amped up model while the Euro/GGEM/UKMET are all much tamer...Ukie is probably the weakest, least significant of the 3. Euro hangs back an inverted trough which adds significantly to the already robust snow totals on that run, but way too early to really worry about a 12/20/08 repeat. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted December 8, 2016 Share Posted December 8, 2016 12/11 completely off the table at this point? Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 5 minutes ago, HoarfrostHubb said: 12/11 completely off the table at this point? May get some flurries or light snow late in the day/evening, but it looks like most of the event holds off until the 12th. If it looks like we may get accumulating snow on the 11th, I'll update the title. Link to comment Share on other sites More sharing options...
J Paul Gordon Posted December 8, 2016 Share Posted December 8, 2016 Hope someone puts up clown maps for amusement factor. Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 17 minutes ago, J Paul Gordon said: Hope someone puts up clown maps for amusement factor. Ginxy often has them for the Euro...I don't even know where to get Euro snow clown maps. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted December 8, 2016 Share Posted December 8, 2016 it's funny how many subtle conditional aspect play a roll there. like, ...the fast overall flow helps that situation. if it slowed down, that wave probably has enough mechanics to torque the flow early and end up west. another, the fast flow helps the cold in that it can't erode out prior to the mid levels taking the qpf mechanics away ...such that the cold wins by time dependence. that in turn helps coastal locations because let's think about this, how often in early-mid dec can we get an all snow in Boston on an wind trajectory that's ene... i 'suppose' we could end up with more c-boundary considering that the antecedent air mass will be pretty fresh and dense ... so ageostrophic component will be bicepy. still, it seems this thing is circumstantially blessed "as is" ... let's hope it stays this way. ha! Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 6 minutes ago, Typhoon Tip said: it's funny how many subtle conditional aspect play a roll there. like, ...the fast overall flow helps that situation. if it slowed down, that wave probably has enough mechanics to torque the flow early and end up west. another, the fast flow helps the cold in that it can't erode out prior to the mid levels taking the qpf mechanics away ...such that the cold wins by time dependence. that in turn helps coastal locations because let's think about this, how often in early-mid dec can we get an all snow in Boston on an wind trajectory that's ene... i 'suppose' we could end up with more c-boundary considering that the antecedent air mass will be pretty fresh and dense ... so ageostrophic component will be bicepy. still, it seems this thing is circumstantially blessed "as is" ... let's hope it stays this way. ha! These fast moving overrunners or "SWFEs" always seem to have an element of "razors edge" to them...its like a delicate balance between the very fast gradient flow and also keeping the mechanics of the system intact for a significant event...but also at the same time being ont he correct side of the ptype gradient. That high configuration to our north though typically gives us at least a little bit more margin for error (I know you know this, but just speaking generally)...if the system tries to amp up a little more, that atmosphere will respond with a stronger ageostrophic tug from that high to balance it...at least to a certain point before the rubber band snaps and we get flooded with mild air if the system decides to go stemwound through Watertown, NY or something....but typically they don't and they get a secondary sfc reflection squeezed out over the Cape or ACK...and if it's not too obnoxious, the mid-levels also dampen out and keep us all snow...though there is definitely room for an ice zone in these should we play the "amped up" game a little too far. Link to comment Share on other sites More sharing options...
wxeyeNH Posted December 8, 2016 Share Posted December 8, 2016 I subscribe to Weatherbell. I can't post the Euro snow total map through Tuesday 18Z but can tell you basically what it shows. Everyone from NYC to the Cape gets some snow. 2" line runs along the south coast to the canal. 6" line runs along the south coast about 20 miles inland to around the lower South Shore. 9" line runs from Hartford to Providence up the Rt 24 line to the Rt 128 area. North and west of that its 9-12" for a wide area of New England up to Central VT and Central NH. Amounts drop off to the north of that. Link to comment Share on other sites More sharing options...
CoastalWx Posted December 8, 2016 Share Posted December 8, 2016 Logan had a screaming east wind at 31-32F and S+ for 12/16/07. Just off the deck was ice cold which helped, and the source region was so dam cold, even after passing over the Gulf of Maine. Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 1 minute ago, CoastalWx said: Logan had a screaming east wind at 31-32F and S+ for 12/16/07. Just off the deck was ice cold which helped, and the source region was so dam cold, even after passing over the Gulf of Maine. Yeah when it's like -10C at 925mb like it was in that 12/16/07 event, it's pretty much impossible to rain even with a wind off the water in December. But yeah, even though we keep mentioning it, I do not think the importance of the position/strength of that high pressure can be overstated. It is the key to this event for getting big snows right into BOS and especially south of there like PVD over to southern CT...it is supplying the cold and enhancing our frontogenesis at the same time. Link to comment Share on other sites More sharing options...
CoastalWx Posted December 8, 2016 Share Posted December 8, 2016 Just now, ORH_wxman said: Yeah when it's like -10C at 925mb like it was in that 12/16/07 event, it's pretty much impossible to rain even with a wind off the water in December. But yeah, even though we keep mentioning it, I do not think the importance of the position/strength of that high pressure can be overstated. It is the key to this event for getting big snows right into BOS and especially south of there like PVD over to southern CT...it is supplying the cold and enhancing our frontogenesis at the same time. I cringe when I hear the "east winds mean death to snow lovers." I mean sure I understand what they mean by saying this, but it's much much more involved, then a broad brushed dead sea scroll commandment from the early days of forecasting. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted December 8, 2016 Share Posted December 8, 2016 Such a flip to winter with that high. I suppose it really starts tomorrow Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 1 minute ago, HoarfrostHubb said: Such a flip to winter with that high. I suppose it really starts tomorrow Yeah it's actually the same high pressure system that is affecting us this weekend with the cold shot...it just "rebuilds" to the northwest as that confluence approaches from the west rather than sliding off the coast completely. You can see it in the image in the first post of this thread...the main high is offshore, but it has the strong arm to the northwest of it rebuilding north of Maine. It's an ideal scenario too because it is already in the environment of a fresh antecedent airmass. That type of airmass is going to be quite dense and provide the type of resistance we are hoping for assuming a reasonable storm track. Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 Not that this is a surprise to anyone these days, but the Euro ensembles are basically like the OP run. Link to comment Share on other sites More sharing options...
ajisai Posted December 8, 2016 Share Posted December 8, 2016 So is this sustained event from Mon - Wed. Or will it give a break on Tues? Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 3 minutes ago, ajisai said: So is this sustained event from Mon - Wed. Or will it give a break on Tues? I'd be pretty surprised if we saw basically 60 hours of snow unabated. We did pull it off (except maybe a brief lull at times) in that Feb 7-9, 2015 event, but those are the exception rather than the rule. If the upper levels played out exactly like the Euro showed, then yeah, we'd have a really long duration event due to the IVT hanging back. But it's good to be skeptical of that until closer. We also don't know if we'll even get a separate event out in the Dec 14-15 time range...some models have it but others are a whiff. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted December 8, 2016 Share Posted December 8, 2016 It will def start snowing Sunday afternoon in Western areas at least Link to comment Share on other sites More sharing options...
Typhoon Tip Posted December 8, 2016 Share Posted December 8, 2016 1 hour ago, ORH_wxman said: These fast moving overrunners or "SWFEs" always seem to have an element of "razors edge" to them...its like a delicate balance between the very fast gradient flow and also keeping the mechanics of the system intact for a significant event...but also at the same time being ont he correct side of the ptype gradient. That high configuration to our north though typically gives us at least a little bit more margin for error (I know you know this, but just speaking generally)...if the system tries to amp up a little more, that atmosphere will respond with a stronger ageostrophic tug from that high to balance it...at least to a certain point before the rubber band snaps and we get flooded with mild air if the system decides to go stemwound through Watertown, NY or something....but typically they don't and they get a secondary sfc reflection squeezed out over the Cape or ACK...and if it's not too obnoxious, the mid-levels also dampen out and keep us all snow...though there is definitely room for an ice zone in these should we play the "amped up" game a little too far. right ..and when you're winning, sometimes it seems like you're getting the 10% chance for success to work out 100% of the time - i know that makes no sense, but it does. because then you have to suffer 9 set ups that are indistinguishable from this where you never do. but let's not count eggs before hatching ... we have 'won' a g-damn thing yet. just we are inside of d5 so we're on the slope of the hockey-stick at this point so we have cautious certainty we'll call it. Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 3 minutes ago, Typhoon Tip said: right ..and when you're winning, sometimes it seems like you're getting the 10% chance for success to work out 100% of the time - i know that makes no sense, but it does. because then you have to suffer 9 set ups that are indistinguishable from this where you never do. but let's not count eggs before hatching ... we have 'won' a g-damn thing yet. just we are inside of d5 so we're on the slope of the hockey-stick at this point so we have cautious certainty we'll call it. Yeah we're just approaching "lethal" range for the Euro...not quite there yet...obviously it is encouraging to see the solution become better as we approach that point, but we're still far enough out where relatively large changes can occur from cycle to cycle...so some caution is warranted. Link to comment Share on other sites More sharing options...
TalcottWx Posted December 8, 2016 Share Posted December 8, 2016 SWFE... usually a 12 hour bout of the good stuff, at least in the past. Hope everyone enjoyed their summer! Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted December 8, 2016 Share Posted December 8, 2016 BOX A plowable snow is possible in Boston, but higher risk northwest of city. Too much of an east wind can quickly change city over to rain. Link to comment Share on other sites More sharing options...
8611Blizz Posted December 8, 2016 Share Posted December 8, 2016 8 minutes ago, HoarfrostHubb said: BOX A plowable snow is possible in Boston, but higher risk northwest of city. Too much of an east wind can quickly change city over to rain. I find that reasonable to say, conditions have to be just right if we are to not change to rain in early December along the coast. Also a little far out to predicting plowable snows imo. Link to comment Share on other sites More sharing options...
TauntonBlizzard2013 Posted December 8, 2016 Share Posted December 8, 2016 I'm definitely skeptical of some of the higher numbers printed out here (10"+) Isnt around 10" about the max you could expect with a SWFE? Unless some other elements come in to play here, kind of like the euro shows.... I'd be cautious of expecting wide spread 6"+ Link to comment Share on other sites More sharing options...
TauntonBlizzard2013 Posted December 8, 2016 Share Posted December 8, 2016 Just now, 8611Blizz said: I find that reasonable to say, conditions have to be just right if we are to not change to rain in early December along the coast. Also a little far out to predicting plowable snows imo. Still 4+ days out.... enough can change that there really isn't a need to signal anything yet Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 1 minute ago, TauntonBlizzard2013 said: I'm definitely skeptical of some of the higher numbers printed out here (10"+) Isnt around 10" about the max you could expect with a SWFE? Unless some other elements come in to play here, kind of like the euro shows.... I'd be cautious of expecting wide spread 6"+ Yeah it's early to really be throwing around numbers anyway this early...but we're not getting double digits unless the IVT hangs back...it can happen...it did in 2008, but we'll want to wait until we are closer in before worrying about that. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 8, 2016 Share Posted December 8, 2016 1 minute ago, ORH_wxman said: Yeah it's early to really be throwing around numbers anyway this early...but we're not getting double digits unless the IVT hangs back...it can happen...it did in 2008, but we'll want to wait until we are closer in before worrying about that. Nice early test for the Northeast WFOs. Hopefully we can all restrain ourselves and take a measured approach to the forecast. Link to comment Share on other sites More sharing options...
ORH_wxman Posted December 8, 2016 Author Share Posted December 8, 2016 4 minutes ago, OceanStWx said: Nice early test for the Northeast WFOs. Hopefully we can all restrain ourselves and take a measured approach to the forecast. Just wait until the inevitable NAM runs that try and drop 1.2" of QPF just from isentropic lift....there's always a few that can't resist the temptation. Link to comment Share on other sites More sharing options...
CoastalWx Posted December 8, 2016 Share Posted December 8, 2016 It's a test for my group too. At least most understand the model enigma that is ORH and freezing precip. And low clouds for that matter. Link to comment Share on other sites More sharing options...
CoastalWx Posted December 8, 2016 Share Posted December 8, 2016 It is definitely a task to get some people off sim radar and QPF and focus on things that involve snow growth and all those processes we try to challenge model QPF output with. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 8, 2016 Share Posted December 8, 2016 1 minute ago, ORH_wxman said: Just wait until the inevitable NAM runs that try and drop 1.2" of QPF just from isentropic lift....there's always a few that can't resist the temptation. "That's what the model gave me" We hear it every year. And models are already borderline there, with the Euro and GFS both hovering near 1" QPF. Link to comment Share on other sites More sharing options...
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