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December Mid-Long Range Discussion


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No wild guess about it. He lives and dies by the Euro and as far as he is concerned the GFS is Sierra Bravo (BS). :)

Looking at day 10 though it does look like it may be setting something up for late XMas eve into Xmas.

but the euro ens mean at 240 hours does not seem to pick up the shortwave that the operational obviously uses to generate the storm. It (the operational) may verify but honking something 12 days in the future is pretty funny as the model also likes to wrap up storms in the longer range at times.

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Help me understand this. If the baroclinic zone is the boundary of cold/warm, wouldn't the track of a single low be along the coast this time of year and not through the piedmont?

Not when the east is flooded with warm air such that the baroclinic zone is pushed way up to our north and west. That is the problem...

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but the euro ens mean at 240 hours does not seem to pick up the shortwave that the operational obviously uses to generate the storm. It (the operational) may verify but honking something 12 days in the future is pretty funny as the model also likes to wrap up storms in the longer range at times.

To be fair to DT he did mention that the ensembles didn't show it. But he did feel if this piece of energy didn't make it through that at some point some would because of the roaring Pac jet. I would just post his comment but am not sure if it is allowed.

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The CPC super ens mean from Dec 13 has a cold but not very snowy look for the days leading up to and including Christmas. The trough is little too far east and suggests after the rain event coming up early next week that the pattern is likely to be drier than normal.

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Looking at the analogs and snow is pretty discouraging. The only snow events were Dec 17, 2010 which gave us a light dusting and Dec 26th which was a big storm that just didn't develop quickly enough for us. It left us in the famous snow hole. None of the other years had any snow earlier than 9 days past the centered mean (Dec 24). Last night's operational Euro looked interesting at 240 hours but based on its own ens mean, it looks like an outlier as the mean does not show the shortwave that the euro suggests would be approaching us around Christmas eve. The good news is that the pattern is not one that is likely to be handled real well as the negative PNA fights the favorable eastern Canada blocking. I still think it unlikely we see accumulating snow before Christmas but that's just a wag in this pattern. You'd probably be wiser to listen to Bob Chill's guess at a window.

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24 hours ago some guidance was starting to show a more favorable pacific pattern but now they seem to be backing off on that. The blocking right now is tempting to believe something might happen but I am skeptical as long as the pacific is this ridiculously hostile. It has to relax some or we are fighting a losing battle here. We don't need a perfect pacific setup with the blocking the way it is...at least not to get some overrunning or moderate events but with the PNA as negative as it is, its going to continue to force energy to try to cut to our west and north. Even with the block...we will be dealing with a predominately SW flow and cut off from cold air being able to really establish itself, especially ahead of a storm system. Even if a storm is shunted east, it will be hard to get it to deepen in a favorable way for us...basically I see a pattern where systems try to cut to the lakes, get blocked and then wash out east but with a marginal air mass and no mechanism to encourage cyclogenesis in a favorable spot for us. New England may do very well with this pattern but until the PNA gets closer to neutral we are probably toast for significant snows here. The question is, with the Pacific SST's as ugly as they are right now... will we get any period of at least neutral PNA this winter or is this it...are we doomed to be stuck with a consistent solidly -PNA right through the winter and waste a really good NAO/AO pattern. I suck at long range forecasting so I would love to hear from those with a better chance of contributing to that discussion.

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I still think it unlikely we see accumulating snow before Christmas but that's just a wag in this pattern. You'd probably be wiser to listen to Bob Chill's guess at a window.

Heh, listening to me is precarious and dangerous at best. lol

My logic is pretty simple. The look is "ok" to "good" and it's been consistent in some form or another. I worry about long leads as much as anyone but the evolution is logical. So at the very least we have a bit of potential with a relatively amplified pattern and some aob normal temps.

The second part of my logic is that we have moved out of a pretty dry pattern coast to coast and have a fair amount of energy working around the large scale circulation. I would expect that to continue and not just shut off like a faucet.

The last part of my logic is simply statistical. We've been snowless for quite some time now. So much so that it's easy to be pessimistic about any chances. And would make you right a heck of a lot more than wrong lately but that doesn't mean you will continue to be right going forward.

I get excited when I see things and I think that sometimes my excitement comes through as me thinking high probability events or windows. That's not the case at all. I simply see the potential for a productive window. Like 60% chance at seeing some snow but less than 15% chance at a larger event (like 6"+ or something like that). That seems like a reasonable view. It's not like I'm saying days and days of snow or anything like that.

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24 hours ago some guidance was starting to show a more favorable pacific pattern but now they seem to be backing off on that. The blocking right now is tempting to believe something might happen but I am skeptical as long as the pacific is this ridiculously hostile. It has to relax some or we are fighting a losing battle here. We don't need a perfect pacific setup with the blocking the way it is...at least not to get some overrunning or moderate events but with the PNA as negative as it is, its going to continue to force energy to try to cut to our west and north. Even with the block...we will be dealing with a predominately SW flow and cut off from cold air being able to really establish itself, especially ahead of a storm system. Even if a storm is shunted east, it will be hard to get it to deepen in a favorable way for us...basically I see a pattern where systems try to cut to the lakes, get blocked and then wash out east but with a marginal air mass and no mechanism to encourage cyclogenesis in a favorable spot for us. New England may do very well with this pattern but until the PNA gets closer to neutral we are probably toast for significant snows here. The question is, with the Pacific SST's as ugly as they are right now... will we get any period of at least neutral PNA this winter or is this it...are we doomed to be stuck with a consistent solidly -PNA right through the winter and waste a really good NAO/AO pattern. I suck at long range forecasting so I would love to hear from those with a better chance of contributing to that discussion.

We are going to be stuck for a while...I said until January 15th a week or 2 back but that is a WAG.....The latest GFS ens have the same exact pattern for 384 straight hours....it has backed off the -epo idea....that is probably our 1st step...get a -epo and have the ridging bleed into the PNA region....I said it would be a backloaded winter but that is all analog based so low confidence, though my analogs are pretty much working perfectly so far...

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isn't that what we in the mid atlantic would want so that the cold air digs farther south setting up a good chance for the next storm (if there is one)????

If there was a high but all the low pressure over Montana suggests the next low tracks towards Iowa and that track would bring back some warmer air ahead of the next system assuming it doesn't shear apart .

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The GFS dealys bringing the nice cold air until the 22 or 23rd but then it looks cold and pretty dry for awhile (beyond Christmas) for what little that is worth.

It wants to give us at least a shot at a storm around 12/27...which is in fantasy land but I would be more bullish on that window with an actual cold airmass in place.....we could get a snow to rain event or something like that

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If there was a high but all the low pressure over Montana suggests the next low tracks towards Iowa and that track would bring back some warmer air ahead of the next system assuming it doesn't shear apart .

Yeah I still don't see a "permanent" change in the pattern. It's still looking like rain, cold shot and dry, warm up with rain, then cold. Rinse and repeat. I'm really missing Montana where every time it got cold it snowed and when it got warm it was dry. Hoping for that eventual change we've been talking about.

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You've mad a ton of positive posts the last few weeks. I know they are factual, but its depressing.

I think getting legit air here matters...if we do and the GFS suggests we do, then we can get some weak wave to give us 1-2"...some tricky mixy forecast we can track for a few days is a hell of a lot better than 55 and dry

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I still like the run. Maybe I'm totally out to lunch but once the ridge sets up out west I don't see how it's impossible for a piece of energy to come over the top or a 4 corners low to slide underneath. GFS shows a low moving through the sw @ 288. I know it's useless to think there's any skill there but it's the idea I'm talking about anyways.

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Yeah I still don't see a "permanent" change in the pattern. It's still looking like rain, cold shot and dry, warm up with rain, then cold. Rinse and repeat. I'm really missing Montana where every time it got cold it snowed and when it got warm it was dry.

I think the cold after about the 23rd may last longer though it still probably won't be a long term cold pattern as the pacific still isn't great.

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The Pacific is killing us. We do at least get a modestly cold shot. That cold shot will help your Dec call as it will still be above normal for the month but may keep the month from totally torching.

I am dubious...I say we end up -3.5 at best...maybe warmer...DCA is an oven...in ideal cooling conditions tonight we'll probably drop to 39...

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