December 9/10 Storm

[showmethesnow]

GEFS pretty much in lockstep with its previous run.

[NoVaWx]

Not even in a nino still misses south. If it was a Nina it’d go ocean city 

[psuhoffman]

2 hours ago, showmethesnow said:

The models have been all over the place with the energy rotating through eastern Canada so there is hope. But at some point you would think they would get that nailed down and I am thinking that time is getting near. A day maybe? Two on the outside? 

 

2 hours ago, C.A.P.E. said:

Probably yes. And even though they have been sort of all over with the discrete pieces of energy, the general outcome is the same. I was hoping we would see things become a bit more amped out west with a sharper s/w dropping in to interact with the southern energy- something like the CMC had. I guess thats still a possibility. Still need some relaxation to our NE though.

The problem is it's not just one vort that's the problem. It's the larger scale vortex that's placing the NS train of vorts through New England. If one isn't there another one comes along. The whole thing needs to lift more but instead it's been trending south a bit over the last 72 hours and it's totally offset the positive trends with the stj that I expected. 

The whole configuration up there could be off but that's a bigger get than one discreet vort being off. 

[CAPE]

Another interesting read from Mt Holly this AM. They are not quite convinced that the models are currently depicting the ultimate outcome.

Operational guidance seems to be converging on a solution in
which a secondary low develops on the coast Monday night in
vicinity of the first low 24 hours prior. The model tendencies
are similar to the first low (CMC farthest north; ECMWF to the
south), but the GFS is slower with this second low (an obvious
result of the slower trend to the central U.S. perturbation).

What does all of this mean? My conclusion is that the models
converging on a solution may be a tempting lure, but I am not
biting quite yet. The perturbations in play here remain offshore
(prior to the 00z simulations, anyway), so I suspect some
decent initialization errors are contributing to model
volatility. Perhaps as importantly, the complex interactions of
these perturbations are extremely sensitive to
positioning/orientation/strength of the individual phenomena,
which is a telltale sign to use caution in the use of
deterministic solutions as a forecast starting point. I used a
healthy blend of continuity, ensemble guidance, and multi-model
consensus as a starting point, only subtly modifying the
forecast to account for the increased southern-track consensus.
Finally, I should note that we are still in the time window in
which models tend to be too far south and too progressive with
the southern- stream portion of these systems, so I maintained a
broad-brush approach to distribution of PoPs (and timing) as a
result of the remaining large uncertainty.

[showmethesnow]

1 minute ago, psuhoffman said:

 

The problem is it's not just one vort that's the problem. It's the larger scale vortex that's placing the NS train of vorts through New England. If one isn't there another one comes along. The whole thing needs to lift more but instead it's been trending south a bit over the last 72 hours and it's totally offset the positive trends with the stj that I expected. 

The whole configuration up there could be off but that's a bigger get than one discreet vort being off. 

I agree the bigger problem is the PV itself. But if we could get a little better timing and/or separation between the energy rotating around it it might give us enough relax at a crucial time to at least get DC into some half decent action. As far as up in my neck of the woods I have all but given up on it.

[CAPE]

13 minutes ago, psuhoffman said:

 

The problem is it's not just one vort that's the problem. It's the larger scale vortex that's placing the NS train of vorts through New England. If one isn't there another one comes along. The whole thing needs to lift more but instead it's been trending south a bit over the last 72 hours and it's totally offset the positive trends with the stj that I expected. 

The whole configuration up there could be off but that's a bigger get than one discreet vort being off. 

Agreed. Thus why I said not to focus on any one discrete vort. Regardless of model to model/run to run variability with timing/location/strength of the individual lobes, the outcome is the same- too much confluence and too suppressive.

[dallen7908]

EPS Percent chances that BWI exceeds 1, 3, 6, and 12" through early next week

[Buddy1987]

33 minutes ago, C.A.P.E. said:

Another interesting read from Mt Holly this AM. They are not quite convinced that the models are currently depicting the ultimate outcome.

Operational guidance seems to be converging on a solution in
which a secondary low develops on the coast Monday night in
vicinity of the first low 24 hours prior. The model tendencies
are similar to the first low (CMC farthest north; ECMWF to the
south), but the GFS is slower with this second low (an obvious
result of the slower trend to the central U.S. perturbation).

What does all of this mean? My conclusion is that the models
converging on a solution may be a tempting lure, but I am not
biting quite yet. The perturbations in play here remain offshore
(prior to the 00z simulations, anyway), so I suspect some
decent initialization errors are contributing to model
volatility. Perhaps as importantly, the complex interactions of
these perturbations are extremely sensitive to
positioning/orientation/strength of the individual phenomena,
which is a telltale sign to use caution in the use of
deterministic solutions as a forecast starting point. I used a
healthy blend of continuity, ensemble guidance, and multi-model
consensus as a starting point, only subtly modifying the
forecast to account for the increased southern-track consensus.
Finally, I should note that we are still in the time window in
which models tend to be too far south and too progressive with
the southern- stream portion of these systems, so I maintained a
broad-brush approach to distribution of PoPs (and timing) as a
result of the remaining large uncertainty.

Def an interesting read but one we are not naive about either. You always do a good job staying on top of these things! Appreciate all your insight when given.

[mappy]

34 minutes ago, C.A.P.E. said:

Another interesting read from Mt Holly this AM. They are not quite convinced that the models are currently depicting the ultimate outcome.

Operational guidance seems to be converging on a solution in
which a secondary low develops on the coast Monday night in
vicinity of the first low 24 hours prior. The model tendencies
are similar to the first low (CMC farthest north; ECMWF to the
south), but the GFS is slower with this second low (an obvious
result of the slower trend to the central U.S. perturbation).

What does all of this mean? My conclusion is that the models
converging on a solution may be a tempting lure, but I am not
biting quite yet. The perturbations in play here remain offshore
(prior to the 00z simulations, anyway), so I suspect some
decent initialization errors are contributing to model
volatility. Perhaps as importantly, the complex interactions of
these perturbations are extremely sensitive to
positioning/orientation/strength of the individual phenomena,
which is a telltale sign to use caution in the use of
deterministic solutions as a forecast starting point. I used a
healthy blend of continuity, ensemble guidance, and multi-model
consensus as a starting point, only subtly modifying the
forecast to account for the increased southern-track consensus.
Finally, I should note that we are still in the time window in
which models tend to be too far south and too progressive with
the southern- stream portion of these systems, so I maintained a
broad-brush approach to distribution of PoPs (and timing) as a
result of the remaining large uncertainty.

really great write-up by them. hopefully today the moving parts become a little bit easier to figure out what they will do. i'm not quite ready to write this off either. 

[Wonderdog]

I have a question. It seems that the storm actually hits a brick wall when the precipitation field tries to enter Missouri. Is that more a result of the HP that is north of the storm or the NS confluence. Seems to me that if that HP would back off a bit, the storm could gain some latitude before it reaches the east coast thereby expanding the precipitation field and then allowing the precipitation to reach DC.

[Round Hill WX]

17 minutes ago, Wonderdog said:

I have a question. It seems that the storm actually hits a brick wall when the precipitation field tries to enter Missouri. Is that more a result of the HP that is north of the storm or the NS confluence. Seems to me that if that HP would back off a bit, the storm could gain some latitude before it reaches the east coast thereby expanding the precipitation field and then allowing the precipitation to reach DC.

It’s not the high pressure that is our problem. It is the 2 features circled. The energy diving into Quebec is pushing our storm eastward. The other circle over ~60W is a wave breaking tropospheric piece of energy which is creating the confluence over the northeast, also shunting the southern stream LP eastward without latitude gain. 

[pasnownut]

54 minutes ago, Round Hill WX said:

It’s not the high pressure that is our problem. It is the 2 features circled. The energy diving into Quebec is pushing our storm eastward. The other circle over ~60W is a wave breaking tropospheric piece of energy which is creating the confluence over the northeast, also shunting the southern stream LP eastward without latitude gain. 

That's a great snapshot of what is and has been one of the problems.  Even though they have shown up at slightly varied degrees, they've always been showing up to spoil the party.  Nice Round Hill.  

[SnowGolfBro]

1 hour ago, mappy said:

really great write-up by them. hopefully today the moving parts become a little bit easier to figure out what they will do. i'm not quite ready to write this off either. 

I think it’s reasonable to stay tuned.  We’ve seen the models jump at this range before. Probably going to slide south but we could still still get an advisory level event if things fall our way

[Wonderdog]

1 hour ago, Round Hill WX said:

It’s not the high pressure that is our problem. It is the 2 features circled. The energy diving into Quebec is pushing our storm eastward. The other circle over ~60W is a wave breaking tropospheric piece of energy which is creating the confluence over the northeast, also shunting the southern stream LP eastward without latitude gain. 

Thanks Round Hill. But something has to start changing at 12z because my snow blower is being delivered in a half hour.

[pasnownut]

6 minutes ago, SnowGolfBro said:

I think it’s reasonable to stay tuned.  We’ve seen the models jump at this range before. Probably going to slide south but we could still still get an advisory level event if things fall our way

IMO we still have time for the northerly adjustments, as we have basically been watching this like a hawk from almost a week ago, so I think we all got a little invested really early on this threat.  I'm likley out, but could see somewhere between DC and Balt, still getting in on some fun.  Hoping it happens for you guys.

[SnowGolfBro]

11 minutes ago, pasnownut said:

IMO we still have time for the northerly adjustments, as we have basically been watching this like a hawk from almost a week ago, so I think we all got a little invested really early on this threat.  I'm likley out, but could see somewhere between DC and Balt, still getting in on some fun.  Hoping it happens for you guys.

I’d be out if i was North of DC. But being 30 miles south of the city i still have a punchers chance of being on the Northern fringe. So I’m in for a couple more days.

[Round Hill WX]

1 minute ago, Wonderdog said:

Thanks Round Hill. But something has to start changing at 12z because my snow blower is being delivered in a half hour.

I tried to attach hours 54-102 of the 6z GFS plot I posted above, but it exceeds the amount of MBs allowed. But if you go to TT and GIF between those hours, you can really see the dynamics occurring. The wave breaking around 60W is the initial confluence. It slightly relaxes as the STJ storm is moving along the GOM, which gives it a chance to gain latitude, but then the northern stream energy comes flying in to finish the job. You were correct in asking about the high pressure because it is "blocking" the storm, but the mechanism keeping the high so stoutly in place are the items I mentioned.

IMO, to get this storm to shift north, the vort energy diving into Quebec will have to come in delayed or further north. For that to happen, the tropospheric wave break will need to be less intense.

Also, there has been discussion about better ridging out west(Boise ID rule) that could help. In theory that is true, however, the retrograding wave break will to be the driver once the storm reaches the east coast.

I hope you get to use your snow blower!

 

[snowmagnet]

22 minutes ago, Wonderdog said:

Thanks Round Hill. But something has to start changing at 12z because my snow blower is being delivered in a half hour.

Just send that snowblower back and maybe things will change by 12z. 

[Eskimo Joe]

Just now, snowmagnet said:

Just send that snowblower back and maybe things will change by 12z. 

I purchased my first snowblower in the fall of 2016 when we moved to Maryland.  We've been cursed since.  I'm sacrificing it on the front lawn this weekend in front of the nativity scene to see if that changes thing.

[Wonderdog]

Just now, snowmagnet said:

Just send that snowblower back and maybe things will change by 12z. 

LOL. But I'm going to use it regardless of what happens. 

[Wonderdog]

11 minutes ago, Round Hill WX said:

I tried to attach hours 54-102 of the 6z GFS plot I posted above, but it exceeds the amount of MBs allowed. But if you go to TT and GIF between those hours, you can really see the dynamics occurring. The wave breaking around 60W is the initial confluence. It slightly relaxes as the STJ storm is moving along the GOM, which gives it a chance to gain latitude, but then the northern stream energy comes flying in to finish the job. You were correct in asking about the high pressure because it is "blocking" the storm, but the mechanism keeping the high so stoutly in place are the items I mentioned.

IMO, to get this storm to shift north, the vort energy diving into Quebec will have to come in delayed or further north. For that to happen, the tropospheric wave break will need to be less intense.

Also, there has been discussion about better ridging out west(Boise ID rule) that could help. In theory that is true, however, the retrograding wave break will to be the driver once the storm reaches the east coast.

I hope you get to use your snow blower!

 

Very  informative.  Thanks again. 

[wawarriors4]

13 minutes ago, SnowGolfBro said:

I’d be out if i was North of DC. But being 30 miles south of the city i still have a punchers chance of being on the Northern fringe. So I’m in for a couple more days.

Thats about how I feel too, being near EZF feel like I still have an outside chance at maybe an inch.......

[mappy]

1 minute ago, Hurricanegiants said:

Plate Well. It’s still Wednesday. I know...wishful blah blah. But if we can tick north tomorrow morning. It would still be only Thursday. Lots can change. It’s not like it’s 24-48 yet.  Here’s to hoping we wake up to better overnight model runs. And when I say better—I mean ANY north improvement. 

psst. today is thursday. 

[ers-wxman1]

12z NAM out to the end of its run looks suppressed over central and southern VA. Plenty of confluence to the north. Doesn’t look like it would come further north on meaningful snow.

[CAPE]

1 minute ago, Hurricanegiants said:

11:00 is our next best model chance correct?

Its actually NAM extrapolation hallucination time right now.

[clskinsfan]

3 minutes ago, ers-wxman1 said:

12z NAM out to the end of its run looks suppressed over central and southern VA. Plenty of confluence to the north. Doesn’t look like it would come further north on meaningful snow.

I dont even think it would get snow into Richmond with that look. Crazy that the models seem to have had the confluence weaker at longer lead times with this event. Often the opposite is true.

[Wonderdog]

4 minutes ago, Eskimo Joe said:

I purchased my first snowblower in the fall of 2016 when we moved to Maryland.  We've been cursed since.  I'm sacrificing it on the front lawn this weekend in front of the nativity scene to see if that changes thing.

Coincidently, I purchased my first snow blower nine years ago,just prior to the December big one!

[BristowWx]

5 minutes ago, Wonderdog said:

Coincidently, I purchased my first snow blower nine years ago,just prior to the December big one!

how many times have we seen the radar blossom to our north in MD when it was forecast not to snow past the Potomac river.  Point is I can see a scenario where the northern edge will be a tick or two further than expected.  EZF is tick one right now...we are tick 2.  oh it wont be Snow heavy at times with blowing and drifting snow possible...but maybe something to spark a smile

[ers-wxman1]

16 minutes ago, clskinsfan said:

I dont even think it would get snow into Richmond with that look. Crazy that the models seem to have had the confluence weaker at longer lead times with this event. Often the opposite is true.

Suppression city.

[Eskimo Joe]

22 minutes ago, ers-wxman1 said:

12z NAM out to the end of its run looks suppressed over central and southern VA. Plenty of confluence to the north. Doesn’t look like it would come further north on meaningful snow.

Looks like we both smoke cirrus this weekend.