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Pattern The Great December Dump

crecre9 said:
Isn't that really just because of a few members skewing the mean? The mean at KHSV is down. In any case, if the GEFS isn't even the same model as the GFS (as in GEFS hasn't been updated yet), then I am not sure that there is significant value in looking for agreement between the GFS Op and the GEFS.
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Sure you can argue that, but even with a few skewed member, even without those, this is a much better look than 00z. We don’t need the FV3 and the GEFS to be in agreement totally, but the FV3 isn’t on an island by itself.
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Rain Cold said:
It's all about timing. We have a pronounced split stream this year. People forget to take that into account when evaluating long range model output. It's bad in the D10 period in general, but throw in a pronounced split flow with waves moving through every couple of days and you will take bad D10 performance and turn it into horrific D10 performance. Our best bet is to look at the big picture pattern present on the models and see if there is agreement that a winter storm is possible. In this case, it is. But the nature of the pattern means that timing has to be nearly perfect. The window isn't very wide.

We've had exactly 3 out of the last 10 GFS runs show a winter storm (outside of some slop in the foothills before the changeover).

Last night's 0z run. You got a high just north of the Lakes. No 50/50, but enough energy in the N/S to phase in with the southern stream and allow for juuuuust enough cold air to support snow.

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The Euro has no phasing...the southern stream system moves in later. Here's the 240 map, as I don't have the 228 one.

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And the CMC at 228:

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Here's the 0z GFS from 12/12. Much better interaction with the N/S. It phases and pulls down the needed cold:

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That one is really nice. I don't anticipate a super cold and suppressed pattern. The southern wave needs to phase with a northern wave. Blocking may help with this. But right now, the flow is way too complicated for the models to remotely predict. Phasing is going to be needed. The good thing is, it's possible. The tough things are, A: it's not probable and B: we won't know for a good while yet.
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I'm confused. You are saying in this case that we need phasing to bring ample cold air South. I thought that phasing actually hurts our snow chances in our area of the Eastern Piedmont of NC. Doesn't phasing cause the LP to track further NW in general, which in turn brings the warm nose further NW and closer to us? Or does it just depend on where the phase occurs?
 
mrdaddyman said:
I'm confused. You are saying in this case that we need phasing to bring ample cold air South. I thought that phasing actually hurts our snow chances in our area of the Eastern Piedmont of NC. Doesn't phasing cause the LP to track further NW in general, which in turn brings the warm nose further NW and closer to us? Or does it just depend on where the phase occurs?
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phasing to our west hurts, phasing to the east would bomb the storm out off the coast creating CAA on the backside and a deformation band somewhere with heavy snow/rain/wind, -NAO is helping our storm track along with the 50/50 low, so if you get a phase to our East or southeast, then kaboom
 
mrdaddyman said:
I'm confused. You are saying in this case that we need phasing to bring ample cold air South. I thought that phasing actually hurts our snow chances in our area of the Eastern Piedmont of NC. Doesn't phasing cause the LP to track further NW in general, which in turn brings the warm nose further NW and closer to us? Or does it just depend on where the phase occurs?
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Phasing can either help or hurt. It depends on where the phase happens. The 1993 storm we were playing around with yesterday phased too far west to help us farther east. We got mostly rain. The December 2000 martha focker storm phased too far east, and we got missed. In this case, we don't have any sort of an antecedent cold air mass in place. So a southern stream wave moving west to east by itself is not going to be enough. So, we need a northern stream vort to phase with the southern stream energy. That would cool the column just enough to support snow over the upper SE. If that doesn't happen, the way it looks now, we are all rain. And it needs to happen not too far north or west, or we rain.
 
Myfrotho704_ said:
phasing to our west hurts, phasing to the east would bomb the storm out off the coast creating CAA on the backside and a deformation band somewhere with heavy snow/rain/wind, -NAO is helping our storm track along with the 50/50 low, so if you get a phase to our East or southeast, then kaboom
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Does that help folks south/southeast of the Apps?


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ATLwxfan said:
Does that help folks south/southeast of the Apps?


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If the phase is strong enough/low is strong enough, that would allow some snow on the backside close to your area with a strong low vs a sheared out mess with cold rain, but it’s hard to get snow to far west with those stronger storms, it’s either heavy snow to nothing with a quick drop off
 
Rain Cold said:
Phasing can either help or hurt. It depends on where the phase happens. The 1993 storm we were playing around with yesterday phased too far west to help us farther east. We got mostly rain. The December 2000 martha focker storm phased too far east, and we got missed. In this case, we don't have any sort of an antecedent cold air mass in place. So a southern stream wave moving west to east by itself is not going to be enough. So, we need a northern stream vort to phase with the southern stream energy. That would cool the column just enough to support snow over the upper SE. If that doesn't happen, the way it looks now, we are all rain. And it needs to happen not too far north or west, or we rain.
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I'd say without cold air in place already our odds are stacked against us.
 
Can’t say I’m excited or seeing anything until the 2nd or 3rd week of January. Need a pattern change not an individual storm to track. I believe pattern favors rain east of the mtns with occasional mix in the mountains like Boone.
 
Snowless & Grumpy said:
I'd say without cold air in place already our odds are stacked against us.
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Exactly. And that's why I have never been excited about the potential with this. But you still have to give it a look, because there is just no way to know for sure 8-10 days out. The pattern is not my favorite, though.
 
BirdManDoomW said:
Can’t say I’m excited or seeing anything until the 2nd or 3rd week of January. Need a pattern change not an individual storm to track. I believe pattern favors rain east of the mtns with occasional mix in the mountains like Boone.
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Probably going to be right here.
 
With an active southern stream and it being December you are gonna see plenty of major winter storms modeled. I would rather see major cold outbreak below 10 degrees in the Charlotte-Raleigh corridor. Right now the pattern is so wet the cold is only doing favors west of the blue ridge back into Mississippi/Alabama. I wouldn’t be surprised to see a another winter event from Louisiana back into Tennessee and points south again with the east being largely cold rain in the Carolinas.
 
CAD is the only thing that can really do anything in this warming trend on the models. So I wouldn’t be too worried about the warmth if we can get another CAD event pop up but that’s likely NC northward.
 
Ilovesnow28 said:
What about us folks in central Alabama and Georgia?
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It’s fantasy but with a track like that moving across the GOM Alabama would score. Anything moving east along the coast or a little south of the coast is golden. A lot better then the Miller BSs we haven seen.


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