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December pattern/forecast thread


weathafella

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3 hours ago, powderfreak said:

Oh man that's close...like 0C to -1C at H7/H85/H925 here and a lot of QPF.

Wildcat-Sunday River-Sugarloaf are just that extra 1-2C cooler aloft and damn that's a lot of snow next week.  Some 36" totals in Maine on the EURO.  But yeah wintery week in NNE, even if sleet and freezing rain east of the Greens then getting into snow deeper cold to our NE.  

Yes going to be close but sigs are in place for a high qpf storm from you to Caribou , snow ??

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Might be worth checking out the partial thickness' for that secondary that develops out there later next week. being there at all in the models signifies that the lowest levels must have some decent cold/BL resistant air inplace; could force some sort of secondary and holding onto some sort of ptypes contention into central NE. 

 

One thing I'm also thinking about is that the ridge since summer has tended to be over assertive in the middle range. Should that correct just slightly less amplified as that bag of disturbances coming through ... CAF and other mechanics play more of a roll   

 

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Just now, USCAPEWEATHERAF said:

We also have March this winter, it won't be like last year, it will be near average for the most part.  Below average temperatures from December 4th onward.

Below average temps from Dec 4th...you can't possibly know that going forward.  For a few days sure...but you make it sound like it's a done deal from Dec 4th on..and that is rather misleading.  I think there is going to be a lot of back and forth with regard to temps...as is usually the case.

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38 minutes ago, Typhoon Tip said:

Might be worth checking out the partial thickness' for that secondary that develops out there later next week. being there at all in the models signifies that the lowest levels must have some decent cold/BL resistant air inplace; could force some sort of secondary and holding onto some sort of ptypes contention into central NE. 

 

One thing I'm also thinking about is that the ridge since summer has tended to be over assertive in the middle range. Should that correct just slightly less amplified as that bag of disturbances coming through ... CAF and other mechanics play more of a roll   

 

I mentioned it in the November threat, but the euro implies some icing into NH and perhaps nrn ORH county. 

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It's not only the SSTA gradient, but also the extensive Siberian snow cover that has induced jet enhancement over the Far East/W Pac. There are other factors as well which have been contributing to excess momentum.

Regarding the stratosphere, I see a pattern conducive for wave-1 convergence which is reflected in model data for the medium term (and subsequently a minor weakening), but the tropospheric regime thereafter (second week of December) appears to transition quite unfavorable for any effective Rossby wave propagation. Wave-2 has been extremely low and should remain there. I think the stratospheric vortex will generally strengthen as December progresses, following one wave-1 attack. The BDC is more active this year compared to last, but its effects might be mitigated by other factors.

On the ECMWF ensembles, we see that the AO/NAO domain higher than normal geopotential heights are essentially dissolved by the end of the run. This will be something important to monitor as we move forward.

I actually think that 12/5-7 period might be a better window of opportunity for "something" at the coast rather than the second week of December. There will be a contemporaneous pulse of conducive -NAO and poleward Pacific ridging, as one of those short waves traverses the CONUS. The Atlantic side pattern may worsen as we move into the second week of December.
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11 minutes ago, NorEaster17 said:

That brings up a good question actually. How many times has it split before Jan 1st vs After. I know it has and I dont believe December is "early" to do so but not sure how often it has. 

 

1 split SSW before January 1st since the late 1950s, and 6 displacement SSW's prior to Jan 1st. All 6 displacements occurred in an easterly QBO regime, and the one split occurred in a +QBO. It's very rare, bottom line.

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I thought the overall look was good though after this week. If you're realistic and accept the fact that not every storm can be white....it's the best chance we've had in years to be honest. It's not saying much, but I'd take it. Yeah I guess you walk the line...but that's how it goes. That's quite the poleward ridge. 

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45 minutes ago, 40/70 Benchmark said:

Keep waiting. 

Bottom line...coastal plane may wait much of Dec...had  better hope for gradient

 

Cmon man you know better than this. Things can pop in the upcoming pattern. As Scott says this is the best looking Dec pattern coming up up in years. Negative EPO can deliver and usually does. 

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8 minutes ago, CoastalWx said:

It's a little west of the EPO domain. 

 

Which is why - especially from coastal SNE southward - sufficient downstream blocking is a prerequisite for favorably tracking short waves. With a poleward ridge / concomitant W US trough, there will be a propensity for individual short waves pushing warmth up the coast. The ECMWF ensembles generally lose the NAO/AO support after December 7th which would be problematic for coastal SNE southward. Some of the guidance suggestive of rapidly strengthening zonal winds up at 10hpa would be consistent with a neutralizing NAO/AO, but we'll see. 

Like I said yesterday, I'd be fairly optimistic if I lived in interior SNE northward over the next few weeks. That end of the first week of Dec interests me a little for the coast if we can get a short wave to eject eastward into the 50/50 low/-NAO induced confluence.

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