December Medium/ Long Range

[psuhoffman]

39 minutes ago, MillvilleWx said:

One of the greatest snowstorms I ever witnessed. Had 4.5”/hr at the height with pure TSSN+ for over a hour. Measured right around 20” in Carney. Randallstown had over 2’ 

The things I would do for that storm again 

I remember people complaining because the snow melted fast because it got into the 50s 3 days after the storm.  Imagine that now. How the mighty have fallen. 

[Kevin Reilly]

20 minutes ago, frd said:

Canada is also well above normal with some of their anomalies in excess of 30 degrees above normal. That indicates no further cold intrusions for the U.S. for the foreseeable future.

Winter over after December 23rd the reindeer didn’t see its antlers shadow 6 days until Spring!

[CAPE]

39 minutes ago, frd said:

Canada is also well above normal with some of their anomalies in excess of 30 degrees above normal. That indicates no further cold intrusions for the U.S. for the foreseeable future.

A week of above normal isnt a disaster.

[87storms]

On 12/18/2024 at 9:03 PM, Kevin Reilly said:

Winter over after December 23rd the reindeer didn’t see its antlers shadow 6 days until Spring!

It is kinda wild, though, that in 3 months it’ll be March Madness. Relying on backloaded winters is risky business. It’ll be go time soon.

[mdhokie]

1 hour ago, frd said:

Canada is also well above normal with some of their anomalies in excess of 30 degrees above normal. That indicates no further cold intrusions for the U.S. for the foreseeable future.

But what about Mongolia?

[WEATHER53]

4 hours ago, psuhoffman said:

Ya we are talking about the same thing just using different terminology 

Yea and now we know 

[WEATHER53]

3 hours ago, MillvilleWx said:

One of the greatest snowstorms I ever witnessed. Had 4.5”/hr at the height with pure TSSN+ for over a hour. Measured right around 20” in Carney. Randallstown had over 2’ 

The things I would do for that storm again 

Big time thunder snow here. 4/5 reports  and 3”ph rates. 

weird sounding in heavy snow-not rumbling ; more like a muffled blast

 

[brooklynwx99]

welp. CP Nino?

[brooklynwx99]

omfg

[CAPE]

18 minutes ago, brooklynwx99 said:

omfg

[brooklynwx99]

2 minutes ago, CAPE said:

you're getting colder air filtering under the block. wouldn't take all that long with a -EPO. the first system around NYD is likely too warm, though any follow up as the block decays could be larger. we'll see. I just like seeing the -EPO/-NAO developing

[CAPE]

29 minutes ago, brooklynwx99 said:

you're getting colder air filtering under the block. wouldn't take all that long with a -EPO. the first system around NYD is likely too warm, though any follow up as the block decays could be larger. we'll see. I just like seeing the -EPO/-NAO developing

Yeah the EPO ridge is the key to getting cold again. The +heights on the panel from your post are mostly a result of the anomalous warmth that builds across Canada in the days prior. Once the EPO ridge develops and colder air starts to get reestablished,  hopefully we see a period with the NAO neutral/slightly negative. The very end of the latest EPS/GEFS hinting at it and the Weeklies are depicting this at least for a time in early Jan. That's probably our first potential window.

[Ralph Wiggum]

2 hours ago, brooklynwx99 said:

omfg

I remember a pattern like this a few years back sorry I don't recall specifically, but there was a sprawling 500mb ridge across Canada, we'll thought this has got to produce, and I'm almost certain we got shutout due to temp issues and cold air source blocked.

[Ralph Wiggum]

2 hours ago, CAPE said:

And there's exactly what it looked like lol. Thanks @CAPE

It is all about where that look progresses at h5. That look itself verbatim really doesn't do much for us.

[Allsnow]

8 minutes ago, Ralph Wiggum said:

I remember a pattern like this a few years back sorry I don't recall specifically, but there was a sprawling 500mb ridge across Canada, we'll thought this has got to produce, and I'm almost certain we got shutout due to temp issues and cold air source blocked.

As @CAPE posted above, that’s not blocking it’s the anomalous warmth in Canada showing those hgts. 

[CAPE]

lol NAM

Someone should start a thread.

[dailylurker]

42 minutes ago, CAPE said:

lol NAM

Someone should start a thread.

For rain? Looks like it gives eastern areas a wet weekend lol

[CAPE]

8 minutes ago, dailylurker said:

For rain? Looks like it gives eastern areas a wet weekend lol

Its snow on the 12km

Other guidance has some precip but mostly rain for our area.

[brooklynwx99]

1 hour ago, Allsnow said:

As @CAPE posted above, that’s not blocking it’s the anomalous warmth in Canada showing those hgts. 

if you advert anomalously warm air up towards Greenland, it can act like a block. nature doesn’t care why heights are high over the Davis Strait as long as they are 

it wouldn’t be the 1-2nd that you’d see a storm risk, it would be more like the 3-6th as the -EPO brings in colder air and the high heights over northern Canada weaken

[frd]

27 minutes ago, brooklynwx99 said:

if you advert anomalously warm air up towards Greenland, it can act like a block. nature doesn’t care why heights are high over the Davis Strait as long as they are 

it wouldn’t be the 1-2nd that you’d see a storm risk, it would be more like the 3-6th as the -EPO brings in colder air and the high heights over northern Canada weaken

Big changes start during this time frame as alluded to you and @CAPE

https://x.com/bamwxcom/status/1869713225148686705

 

[CAPE]

18 minutes ago, brooklynwx99 said:

if you advert anomalously warm air up towards Greenland, it can act like a block. nature doesn’t care why heights are high over the Davis Strait as long as they are 

it wouldn’t be the 1-2nd that you’d see a storm risk, it would be more like the 3-6th as the -EPO brings in colder air and the high heights over northern Canada weaken

It's a bit wonky the way it forms and as advertised it doesn't become the classic rex block with a low in the 50-50 position(trough is displaced further out in the N Atlantic). No cold air around  until the ridge goes up out west. Lets see how persistent it is as we get colder air in place. If it doesn't block/divert the flow and keep HP locked in to our north with storms tracking underneath then it isn't very useful lol. We have seen this pretty frequently in recent winters.

[stormy]

13 hours ago, WEATHER53 said:

And lack of stj influence means lack of Miller As to run into our cold air at the right time and from the snow making direction 

Thanks!   You are 100% right!

[CAPE]

1 hour ago, frd said:

Big changes start during this time frame as alluded to you and @CAPE

https://x.com/bamwxcom/status/1869713225148686705

 

The big 3 global ensembles have a significantly -EPO at the end of their 0z runs. Slightly -AO and NAO. GEFS surface temps still a bit on the warm side but the Euro has about average trending slightly below. Canadian a bit colder.

[psuhoffman]

4 hours ago, Ralph Wiggum said:

I remember a pattern like this a few years back sorry I don't recall specifically, but there was a sprawling 500mb ridge across Canada, we'll thought this has got to produce, and I'm almost certain we got shutout due to temp issues and cold air source blocked.

2021 

[rjvanals]

29 minutes ago, psuhoffman said:

2021 

If we’re talking about Jan/Feb 2021 we got unlucky as the storms hit to the south of DC or just north of DC https://www.washingtonpost.com/weather/2023/12/27/dc-snow-hole/

We also had the storm around Presidents’ Day where a small warm layer at ~5000 ft turned a 6-10 inch snow event into a sleet fest around DC despite cold low level temps.

We probably had a bottom 10 percent outcome for that set up and I’d take our chances w it again. 

[psuhoffman]

2 hours ago, CAPE said:

It's a bit wonky the way it forms and as advertised it doesn't become the classic rex block with a low in the 50-50 position(trough is displaced further out in the N Atlantic). No cold air around  until the ridge goes up out west. Lets see how persistent it is as we get colder air in place. If it doesn't block/divert the flow and keep HP locked in to our north with storms tracking underneath then it isn't very useful lol. We have seen this pretty frequently in recent winters.

It's not a block, but it is a high latitude ridge.  Yes there is a difference and a true block which always evolves from retrogression or wave breaking is better and that pattern is the best for HECS hunting.  But not all -AO/NAO periods come from retrogression sometimes they can evolve from progression of a heat ridge into Canada and those correlate to snow here also!  No not as much as the perfect unicorn retrograding block.  But a regular good old high latitude heat ridge is still a legitimate way historically for us to get a snowstorm.  This evolution is actually almost identical to what lead to the Feb storm in 2006.  

The pattern started with a full latitude head ridge in the east which got undercut from the west through pattern progression and lead to this...

It's a baby steps thing...what we are looking at around New Years would have to be step one of a process that could lead to a favorable snowstorm pattern here a week later IF things go the right way.  

As for the hyper focus on the EPO... yea it would be helpful if the EPO delivers cold, but there is a reason the EPO along has absolutely no positive correlation to snowfall here!  NONE, ZERO ZIP.  Actually when I looked at every warning snowfall at BWI since 1950 the EPO of all the major indices I evaluated was the least important.  I think more snowstorms happened with a +EPO than negative.  

The fact is we don't just need cold air, we also need a longwave pattern that favors wave amplification at our longitude!  An EPO ridge absent other factors does not do it.  An EPO with a positive AO/NAO actually places us in a northwest flow and waves are washing out on approach.  It's really hard to get a snowstorm in that look.  Worse, without any AO/NAO help when we do get a jet transition and an amplified wave comes along its not going to meet any resistance and so the return flow ahead of it warms our thermals before it arrives...we are too close to the backside of the trough and the warmth is lurking too close to our west for that to work absent other factors like blocking.   Cold dry, warm wet.  That's a typical EPO driven pattern!  No not every single one, once in a while you get super lucky with a year like 2014 or 2015 or some fluke hits like in 2022, but that is the less likely outcome....its much more likely that pattern does not lead to a snowstorm.   Just because most of our snow the last 8 years has come that way does not mean its now the best way to get snow...that is the reason the last 8 years has been by far not even close the least snowy 8 year period in our regions history!  Yes if that kind of pattern persists over and over and over we will luck and fluke our way to some random snow once in a blue moon...but it will continue to be the way it has the last 8 years with below avg snowfall years and scraping by with long stretches of frustration.  An epo driven pattern is not going to be our most likely path to breaking out of this and having a truly snowy period or getting a legit area wide snowstorm.  And sure we take what we can get, if scraps is all we can get eat them....but we don't control any of this so why not root for more?  It's ok to realize we probably aren't going to win the lottery, but its ok to root for it!  

 

Lastly, if we get a pacific to atlantic ridge bridge up top (and those are rarely blocks) and its just not cold enough...the pattern isn't the problem...its just become too warm is!  This is a matter of degrees, sure you can do the whole move the goalposts thing and say well...if that is too warm now we also need the EPO ridge AND we need there to not be a torch period ahead of the longwave pattern, and we need cross polar flow and we need....OMFG at that point it sounds like we live in Atlanta now and the truth is its just not gonna snow much and its probably not worth even tracking.  I mean even in Florida there is some checklist of anomalous factors that if they all lined up could lead to snow...but the point is their checklist is 25 things long and so its just rarely ever going to happen.  If our checklist starts to go from 3 things to 8 or 10 or 15 at some point we've entered the "its just not gonna snow much" territory.  But just because we have a thermal issue now does not mean the AO and NAO are suddenly less important, there is no evidence of that...it just means we are snowing way less.  We still need those other factors to line up to have a good chance of a snowstorm...we just also now need MORE.  

[Ralph Wiggum]

36 minutes ago, psuhoffman said:

2021 

That's it. Pretty sure that was the year of the epic unicorn LR ensemble pattern as well. That ridging in central Canada was forecast to progress into the NAO region across the ensembles and become an epic block....our savior. Iirc it ended up being too much of a good thing?

[psuhoffman]

BTW, given my modest snowfall forecast for this winter...I did not expect nor predict we do get a big snowstorm...or even a moderate one...to get to those numbers we just need a few minor events.  But that does not mean there is no chance and that I am not rooting for it.  Just because I expect it to be a horrible year doesn't mean I don't want it to turn out better or that I am not looking for the chance it does.  Flukes happen.  2000 was a god awful horrible pattern 90% of that winter...it very well could have ended the same as 2002 or 2008 or 2012 as a complete dud...but we got one week with a decent pattern and hit the lottery.  I am rooting for that again.  That can happen in any year, nina or not.  

[Ralph Wiggum]

3 minutes ago, psuhoffman said:

It's not a block, but it is a high latitude ridge.  Yes there is a difference and a true block which always evolves from retrogression or wave breaking is better and that pattern is the best for HECS hunting.  But not all -AO/NAO periods come from retrogression sometimes they can evolve from progression of a heat ridge into Canada and those correlate to snow here also!  No not as much as the perfect unicorn retrograding block.  But a regular good old high latitude heat ridge is still a legitimate way historically for us to get a snowstorm.  This evolution is actually almost identical to what lead to the Feb storm in 2006.  

The pattern started with a full latitude head ridge in the east which got undercut from the west through pattern progression and lead to this...

It's a baby steps thing...what we are looking at around New Years would have to be step one of a process that could lead to a favorable snowstorm pattern here a week later IF things go the right way.  

As for the hyper focus on the EPO... yea it would be helpful if the EPO delivers cold, but there is a reason the EPO along has absolutely no positive correlation to snowfall here!  NONE, ZERO ZIP.  Actually when I looked at every warning snowfall at BWI since 1950 the EPO of all the major indices I evaluated was the least important.  I think more snowstorms happened with a +EPO than negative.  

The fact is we don't just need cold air, we also need a longwave pattern that favors wave amplification at our longitude!  An EPO ridge absent other factors does not do it.  An EPO with a positive AO/NAO actually places us in a northwest flow and waves are washing out on approach.  It's really hard to get a snowstorm in that look.  Worse, without any AO/NAO help when we do get a jet transition and an amplified wave comes along its not going to meet any resistance and so the return flow ahead of it warms our thermals before it arrives...we are too close to the backside of the trough and the warmth is lurking too close to our west for that to work absent other factors like blocking.   Cold dry, warm wet.  That's a typical EPO driven pattern!  No not every single one, once in a while you get super lucky with a year like 2014 or 2015 or some fluke hits like in 2022, but that is the less likely outcome....its much more likely that pattern does not lead to a snowstorm.   Just because most of our snow the last 8 years has come that way does not mean its now the best way to get snow...that is the reason the last 8 years has been by far not even close the least snowy 8 year period in our regions history!  Yes if that kind of pattern persists over and over and over we will luck and fluke our way to some random snow once in a blue moon...but it will continue to be the way it has the last 8 years with below avg snowfall years and scraping by with long stretches of frustration.  An epo driven pattern is not going to be our most likely path to breaking out of this and having a truly snowy period or getting a legit area wide snowstorm.  And sure we take what we can get, if scraps is all we can get eat them....but we don't control any of this so why not root for more?  It's ok to realize we probably aren't going to win the lottery, but its ok to root for it!  

 

Lastly, if we get a pacific to atlantic ridge bridge up top (and those are rarely blocks) and its just not cold enough...the pattern isn't the problem...its just become too warm is!  This is a matter of degrees, sure you can do the whole move the goalposts thing and say well...if that is too warm now we also need the EPO ridge AND we need there to not be a torch period ahead of the longwave pattern, and we need cross polar flow and we need....OMFG at that point it sounds like we live in Atlanta now and the truth is its just not gonna snow much and its probably not worth even tracking.  I mean even in Florida there is some checklist of anomalous factors that if they all lined up could lead to snow...but the point is their checklist is 25 things long and so its just rarely ever going to happen.  If our checklist starts to go from 3 things to 8 or 10 or 15 at some point we've entered the "its just not gonna snow much" territory.  But just because we have a thermal issue now does not mean the AO and NAO are suddenly less important, there is no evidence of that...it just means we are snowing way less.  We still need those other factors to line up to have a good chance of a snowstorm...we just also now need MORE.  

Epic post PSU.

[psuhoffman]

Just now, Ralph Wiggum said:

That's it. Pretty sure that was the year of the epic unicorn LR ensemble pattern as well. That ridging in central Canada was forecast to progress into the NAO region across the ensembles and become an epic block....our savior. Iirc it ended up being too much of a good thing?

Also 2019, its happened a few times lately, it also happened in Dec more recently.  The combo of our source regions being torched and mid latitude warmth caused the SER to link up with the NAO block multiple times recently.  But we still need that longwave configuration we just need it to not be too warm when it happens, and no I don't know how we magically make that happen...but a pattern that puts us on the backside of a trough with no blocking to hold the cold in when an amplification happens is not a winning formula either.