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Everything considered, including comments from several media outlets regarding frigid conditions in the East near Christmas, its not really that cold. We had colder already, teens as low temps were recorded at many locations. That was when we had the record - EPO a while back.

Can you imagine if we get snow cover prior to this arctic beast. What an opposite December from the last 10 years. It does look like a 1960's type winter pattern for a period of time, leading up to and most likely going past the first of the year.

Interesting CPC D+ 11 Analog Composite. Notice the years from the 1960's, 1970's. I believe @Bob Chill mentioned he was looking at 1960's type winter comparisons for this winter.

Well we did it ! Achieved a - 4.0 SD on the AO. Good times should follow. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.daily.ao.nao.pna.aao.gdas.120days.csv The AO looks to remain negative.

Expect some crazy outcomes late week as the jet reverses.

Yep, it looks really cold, and it may have staying power as the - AO regime looks to remain in control. Snowcover will help with the overall cold expanse.

From the book Kocin and Uccellini, there is potential ! I have sinned, forgive me for posting this .

OMG the Holly Grail of Blizzards is a coming................................ Split flow !!! Blocking !!! Arctic Air !!!!

Of potential interest in regards to HL blocking today is the AO might achieve a -4.0 SD . Yesterday I believe it was - 3.35 or close to it. According to Don Sutherland when the AO achieves - 4.0 or deeper reading it has the ability to overpower less friendly indices such as the - PNA. Not saying this is going to be the outcome, but it will be interesting to watch the trends. Also of the note, the AO is not forecast to rise as rapidly once bottomed out then what was modeled a few days ago. So, basically it appears the month of December will feature a mostly or completely negative AO and a significant one of that which will hopefully entices another - AO regime during the upcoming winter season.

Nice to see the moisture nearby with the cold in place.

The PV still looks to be under pressure as we near the end of the month with a couple heat fluxes.

Snap shot near Christmas from the CFS 500 hPa Hgts and Anomalies.

We are talking nationwide cold coming up with a gradual step down with temps, expect higher snowfall coverage in North America as we get closer to Christmas, and lower lattitude storm tracks. Its been a long time waiting for holiday cold and tracking. Rejoice

You're not concerned with the EPS at the end of it's run? It shows - PNA and most significant snowfall would be well to our North and West. Favors the West and Midwest. Of course it's one run , one model. Total speculation. Granted - EPO on the EPS, but not sure we benefit snow-wise.

500mb anomaly clusters from the WPC show very good agreement on the - EPO and West based - NAO regime.

Allen mentioned cold air damning through this period. Looks like low to mid 20's for overnight lows in my area next Tuesday and Wednesday morning.

Hope they are correct this time.

The PNA is modeled to go more neutral towards mid-month. With the - EPO , - AO, and - NAO cold should not be a problem. The pattern is looking very good after the 15 th. Wave breaking may extend the - NAO. Overall should be an active and cold period between the 15 th and Christmas.

Several mets are indicating that leading up to Christmas will be cold. What are you basing toasty on ? Various ensembles show a - EPO leading up to Christmas, a continued - NAO, - AO and a neutral PNA. I hope this year Christmas would at least be seasonal.

The Pac can not get modeled correctly. Or, what psu said. Don't assume any colder scenarios until inside day 7 . However, there have been looks such as the trough in the West with mild air over the East that did have change rapidly in a week's time leading to East Coast snow.

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).