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Several thoughts - the impact later in a season when the Nina starts to weaken, and if so, the Pac might improve in Feb to March, even though most Ninas are front loaded in our area cold and snow-wise. Also, we are nearing the potential for a - 4 SD AO. Implications for another - AO regime later in the winter seems a higher probability. Snow cover, during the past 5 years NH snow cover has been very impressive. many thought with such a wide expanse of snow cover over the NH and especially over North America it would increase the odds of a cold Jan the last few years. But, what evolved the last few years is around mid December most of the North America snow cover was reduced drastically during a turn to warmer conditions accompanied by a - PNA, + AO, + NAO regime. History may not repeat this December to the degree of the last few Decembers. If we can keep the snow cover and repeat in Jan with a - EPO reload / - AO / - NAO we might score . However, we still need the Pac to improve somewhat, at least for a short window of time. Even the end of this month may exhibit a short window for snowfall.

I was hoping for the mid month period, but I feel we need to wait longer based on the pattern . Looking forward to eventual tracking, whether it be late this month, or in Jan or Feb.

I wouldn't get your hopes up. The can is being kicked down the road yet again. The EPS and the GEFS are underestimating the - PNA. We never get inside a 10 day window with a decent pattern, its always days 10 to 15 . So far that has happend three times. To make matters worse the awesome look of the PV under the block is gone so cold air delivery is questionable. We need to wait for a - EPO / improving Pac to deliver a colder air mass to the East. Seems climo history has more merit than modeling. It simply is very difficult to get snow in December.

977 mb and deepening at our latitude. Weather porn at its best.

The present Nina, our climo and the crummy Pac appears to be countering the - AO and - NAO. At least that is my thought. Might be a while for a decent pattern here. According to Don the - PNA regime will last a while. Here is his post on the PNA From @donsutherland1 Statistically, insight regarding strong AO+ values proved useful in heralding the arrival of AO blocking in late November. A sustained AO- regime commenced on November 23. https://www.americanwx.com/bb/topic/58336-november-2022/?do=findComment&comment=6681570 Statistical trends in the PNA following the most similar December 3 cases suggest that, just as is shown on the dynamical guidance, the ongoing PNA- regime will be slow to breakdown. By the end of the third week in December, values should be less negative than they currently are. However, the development of sustained positive values by that time seems unlikely (not zero, but still a less than one-in-three probability).

Wish I saw this sooner, so I could stop looking at the models.

Remarkable seeing how important a + PNA is during the month of December. Also, the importance of a + PNA in Jan and Feb too, thanks for doing this Don !

Excellent thread on the PNA and why it is more negative next week than originally forecasted. Eric states the - PNA next week is just a slight roadblock to that better pattern the evolves later. He feels the best pattern for snow arrives closer to the holidays.

We were debating last year, and other years as well, what is the most important tele for our area ? For snow I think the - AO, but many feel you need a decent Pac. I remember many times when we had a very strong West based block, but the Pac was awful and we never cashed in. Again like you said, it is a Nina, so to be expected. I will believe the snow potential after I measure it on my deck. I am hopeful, but with a fair degree of skepticism. Maybe the pattern requires more time to establish itself.

Check this out - not only highly unusual over Greenland, but notice the split flow mid month on the animation.

Wonder if the real cold arrives later in the month, or in early Jan. with a more robust - EPO reload.

JMA weeklies..... Yikes ! FYI.... I rotated the image aleady.

Wow, have not seen a AO forecast like this in December for many a year. Usually it is going towards + 4. Bring on winter !

Did you happen to check out the extended, GFS? It shows a continuation of blocking. According to HM the mechanisms to support the North Atlantic blocking are supposed to cycle and repeat. You also have to wonder if what occurred in the southern hemisphere during winter is going to occur in the northern hemisphere during our winter.

Data and image Coutesy of Don Sutherland @donsutherland1 Neutral to + PNA certainly raises the odds of snowfall for many locatioins in this image.

As Anthony had mentioned previously, this - NAO regime is not the only one for this winter season. .

Wow, that Greenland block is changing the entire waveguide up North. Incredible ! According to @burgwx the delayed effect of the block puts the highest risk for a major snowstorm between the 15 th and the 20 th. I would like an appetizer and then the Big dog . Woof !!!

When Allan gets excited I know its the real deal.

Just more data on how significant this upcoming Greenland blocking event is going to be.

Yes, signs point to a significant - EPO reload. Of note as well, are signs of a warming event near the pole. The pattern is locked and loaded it would appear. Should the pattern evolve as modeled significant snow cover will be located to our North and West and maybe over our region as well. Appears that the cryosphere will be healthy to deliver the possibility of intense cold originating in NW Canada then moving SE over snow covered grounds with little moderation at a time of very low sun angle and solar output. Something not seen in a very, very long time. A 1960s analog type deal. Also, this is the last day of the month so I give the CFS a decent chance of verifying for December. It should be in its wheelhouse of best skill for the next month.

@CAPE big storm potential leading up to Christmas.

This look appears as one of the more colder and aggressive clusters from @burgwx that he posted yesterday.

There certainly is a connection, just need to find the research. I have read that a - 3 AO in December, or possibly earlier, tend to get repeated during the winter. If a - NAO episode is involved as well it raises the bar for our area and the low lands.

Wow that was awesome ! I know he is a master of using ensemble clustering. He has tons of data where he can compare current modeling to past ensemble clusters.

Well, the cold and storm trifecta you refer to there is actually a possibility based on the evolution of the modeling, but it is only modeling, so...... The - EPO regime should return, the AO is forecast to stay mostly negative, the - NAO may be reinfoirced with wave breaking, the zonal winds are forecast to remain weak or go weaker, the PV is disturbed , and I believe you need low zonal winds to foster a prolonged - NAO period. That is one crazy look.