December Forecast Discussion

[valkhorn]

Canada isnt even that cold. Look how far north the -10C line is.

I see nothing out of the ordinary. Western CA can get relatively warm in the winter due to prevalent weather patterns. Ever heard of a chinook?

Delta I just made the statement that the GFS always drops in a sinker in the middle of the game, Do you agree ?

That's how it works. The storm is still there, but the details are fuzzy. By the way, the energy that moves through on 12/23 is interesting, too.

Look at the ensembles when they come out. That'll give you a bigger clue. I don't think the Euro will be the thing to look at until it's 5-7 days out or less. Just like you don't look at the 84th hour of the NAM or the 384th hour of the GFS.

This run is a swing and a miss.....The problem is, there is tooooo much energy flying around everywhere. This is NOT going to be an easy system to forecast.

Disagree. It still looks good to me. Why are people looking for minute details in a mid range forecast? The odds are stacked against you that you''ll be wrong unless you look at generalities.

[valkhorn]

I think it's a mistake to place too much emphasis on any individual shortwave at this point in time. The best thing to do is focus on the ingredients and the rest will come together in time. The most important pieces to a snowstorm in this pattern are going to be the usual suspects 500mb low over new england that slowly exits and blocking to the north of it. That slows the pattern down and suppresses the system allowing dynamics to take over.

I couldn't have said it better myself.

[metalicwx366]

Next!! Hopefully this isn't a trend.

[IWC]

I couldn't have said it better myself.

i get your point on too much activity for puter to digest. It's still there just needing to clear out in front of it.

[BullCityWx]

I see nothing out of the ordinary. Western CA can get relatively warm in the winter due to prevalent weather patterns. Ever heard of a chinook?

Ok genius, find me some cold air in Ontario and Quebec:

[valkhorn]

Next!! Hopefully this isn't a trend.

The low is still there and still bombs out. All it has to do is change the track by 150 miles and it'll greatly change the situation.

So many nabobs of negativity around here!

[BullCityWx]

I can promise you, unless you're above 3500 feet in elevation, that in the southeast you need eastern canada to be a lot colder than what you see depicted.

[BullCityWx]

Even the best look we've seen all day(12z) was all rain outside of the mountains in almost all locations in the SE.

[valkhorn]

Ok genius, find me some cold air in Ontario and Quebec:

You're looking at it. -5C or so up there is nothing to sneeze at for mid December. When there's a good snowpack, upper air temps can sometimes be much warmer than what's at the surface anyway. Cold air is very dense and sinks.

The low is not going to pull down super arctic air, but you don't need that for a good snow. In fact, the closer the air is to 32F the more snow you'll get. The good -10C is coming down later around the 20th, and the motherload develops at the extreme range of the model.

[Jon]

The two pieces of energy interact much later on this run, phasing much later than previous runs. Look at the vorticity valid tues 0z on both the 0z and 18z & 12z. Just something I noticed and possibly something to keep an eye on subsequent runs.

[BullCityWx]

You're looking at it. -5C or so up there is nothing to sneeze at for mid December. When there's a good snowpack, upper air temps can sometimes be much warmer than what's at the surface anyway. Cold air is very dense and sinks.

The low is not going to pull down super arctic air, but you don't need that for a good snow. In fact, the closer the air is to 32F the more snow you'll get. The good -10C is coming down later around the 20th, and the motherload develops at the extreme range of the model.

You will not get a snowstorm in the SE with Canada that warm. It's a near certainty. The BEST you can hope for is an elevation snowstorm above but even what's depicted tonight isnt an elevation snowstorm.

and No, -5C is fairly warm. Toronto is almost at 0C itself.

[BullCityWx]

The two pieces of energy interact much later on this run, phasing much later than previous runs. Look at the vorticity valid tues 0z on both the 0z and 18z & 12z. Just something I noticed and possibly something to keep an eye on subsequent runs.

We can talk about the different vorts until the cows come home but Griteater is right. There is just no cold air.

[valkhorn]

I can promise you, unless you're above 3500 feet in elevation, that in the southeast you need eastern canada to be a lot colder than what you see depicted.

Not exactly, no. Some of the biggest cold outbreaks for the southeast were from airmasses that went across western Canada and went SOUTH of the great lakes. January 1985, January 1962, December 1989, February 1996 were classic examples. In fact, you get colder outbreaks when they come from western CA because the air doesn't modify over the great lakes.

A lot of times the cold air that comes from southern snows comes from western CA, too.

Seeing as how this run isn't going to be what's happening verbatim, I don't see the reason to criticize it or find fault with it.

[valkhorn]

You will not get a snowstorm in the SE with Canada that warm. It's a near certainty. The BEST you can hope for is an elevation snowstorm above but even what's depicted tonight isnt an elevation snowstorm.

and No, -5C is fairly warm. Toronto is almost at 0C itself.

No it isn't, not for an area with snowpack, or an area that typically sees Hudson Bay freeze over. 850 temps in cold snowpack areas can often be a good bit warmer than surface temps. Take a look at eastern CA sometime. You'll rarely see 850mb temps approach -35C up there in any given winter, but the surface temps can go well below that. Western CA is an even better example.

I've seen many model runs over many winters over Canada and -5C isn't super warm, nor does it give you a good idea of surface temps.

Have patience, and if you're going to cry a river at least put up a flood warning.

One model run you don't like, and you huff and puff.

[WilkesboroDude]

I thought the argument earlier was that dynamic cooling would be our means of getting winter precip?

Anyway, like mentioned above, this solution is not verbatim 7 days out.

[BullCityWx]

I thought the argument earlier was that dynamic cooling would be our means of getting winter precip?

You never ever count on dynamical cooling. Ever.

[Jon]

We can talk about the different vorts until the cows come home but Griteater is right. There is just no cold air.

Well cold air is not something I was thinking would be incredibly involved with this storm. The previous runs were hardly cold, so I figured the cold would be absent in runs to come. But yeah I'd rather look at vort maps, even of its this far out, I like the specifics.

[valkhorn]

I thought the argument earlier was that dynamic cooling would be our means of getting winter precip?

Anyway, like mentioned above, this solution is not verbatim 7 days out.

It is the argument when there's something else to nit pick over. Dynamic cooling can really help a lot with snow in the southeast. I've seen it happen many times. All you need is a little dendrite growth and the temps to be below freezing. You don't need -10C 850mb temps for that, and sometimes surface temps can be colder than 850mb temps if dynamic cooling happens. If the precip rates are strong enough magic can happen.

I remember one strong snowburst in Knoxville that gave us 2 or 3" thanks to dynamic cooling. Upper air temps were not that cold and the temp went from 35F and rain to 33F and heavy accumulating snow in a matter of minutes. MRX totally missed that one, too. So did most of the models.

[BullCityWx]

No it isn't, not for an area with snowpack, or an area that typically sees Hudson Bay freeze over. 850 temps in cold snowpack areas can often be a good bit warmer than surface temps. Take a look at eastern CA sometime. You'll rarely see 850mb temps approach -35C up there in any given winter, but the surface temps can go well below that. Western CA is an even better example.

I've seen many model runs over many winters over Canada and -5C isn't super warm, nor does it give you a good idea of surface temps.

Have patience, and if you're going to cry a river at least put up a flood warning.

One model run you don't like, and you huff and puff.

I'm sure we've had many snowstorms where the 0C line is north of CLEVELAND. I've had it wrong this whole time. my bad.

[WidreMann]

No it isn't, not for an area with snowpack, or an area that typically sees Hudson Bay freeze over. 850 temps in cold snowpack areas can often be a good bit warmer than surface temps. Take a look at eastern CA sometime. You'll rarely see 850mb temps approach -35C up there in any given winter, but the surface temps can go well below that. Western CA is an even better example.

I've seen many model runs over many winters over Canada and -5C isn't super warm, nor does it give you a good idea of surface temps.

Have patience, and if you're going to cry a river at least put up a flood warning.

One model run you don't like, and you huff and puff.

That's great for Canada, but getting that kind of cold air down into the SE requires a colder source region, to account for moderation. Also, your statement about -35 C isn't relevant here. That's in a situation where there is already a very cold airmass in place that's able to get even colder at the surface. With the pattern we're in, Canada is being flooded with moderate air from the Pacific at all levels. There's no way a significant cold pool at the surface will develop with that kind of pattern. Same problem we had in 01/02.

[valkhorn]

You never ever count on dynamical cooling. Ever.

[WidreMann]

Not exactly, no. Some of the biggest cold outbreaks for the southeast were from airmasses that went across western Canada and went SOUTH of the great lakes. January 1985, January 1962, December 1989, February 1996 were classic examples. In fact, you get colder outbreaks when they come from western CA because the air doesn't modify over the great lakes.

A lot of times the cold air that comes from southern snows comes from western CA, too.

Seeing as how this run isn't going to be what's happening verbatim, I don't see the reason to criticize it or find fault with it.

Yes, but that cold air in NW Canada is not heading in this direction, so your point is, again, moot.

And don't come back at me with "well, it may not be in your backyard", because it's not going to be in yours either.

[WidreMann]

Good point!

[BullCityWx]

keep it in the banter thread. thanks.

[valkhorn]

That's great for Canada, but getting that kind of cold air down into the SE requires a colder source region, to account for moderation. Also, your statement about -35 C isn't relevant here. That's in a situation where there is already a very cold airmass in place that's able to get even colder at the surface. With the pattern we're in, Canada is being flooded with moderate air from the Pacific at all levels. There's no way a significant cold pool at the surface will develop with that kind of pattern. Same problem we had in 01/02.

The air didn't moderate that much for the 3 feet to fall in the Smokys thanks to Sandy - and that was in October. Plenty of times there have been good snowstorms in the SE without massive arctic air outbreaks.

And, if you want REALLY cold air, just wait until the end of the run. Most of the winter is still ahead of us, so have some patience and take a chill pill. Or, smoke 'em if you got 'em.

[valkhorn]

keep it in the banter thread. thanks.

Way to stick to the script.

[WidreMann]

The air didn't moderate that much for the 3 feet to fall in the Smokys thanks to Sandy - and that was in October. Plenty of times there have been good snowstorms in the SE without massive arctic air outbreaks.

And the Smokies are several thousand feet up, and that was with a strong storm.

And, if you want REALLY cold air, just wait until the end of the run. Most of the winter is still ahead of us, so have some patience and take a chill pill. Or, smoke 'em if you got 'em.

I'm sure it'll come. Early December was downright frigid, after all. GFS usually nails it!

[BullCityWx]

I'm not trying to be nasty about dynamic cooling but I can only remember 4 times where dynamic cooling worked out in my favor(2/98, 11/00, 3/09 and 12/10). If you're waiting on dynamic cooling east of the mountains in NC and SC, you're normally going to be left waiting as it never happens in time.

[IWC]

ok, Men what does the EURO tell you ?

[WidreMann]

I'm not trying to be nasty about dynamic cooling but I can only remember 4 times where dynamic cooling worked out in my favor(2/98, 11/00, 3/09 and 12/10). If you're waiting on dynamic cooling east of the mountains in NC and SC, you're normally going to be left waiting as it never happens in time.

And even in those cases, we already had other conditions that were marginally favorable. You can't start at 40 and get snow with dynamic cooling and nothing else. Not gonna happen.