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The coldest air of the season so far covers the region. Tomorrow will be another fair but cold day.

Thanksgiving Day will witness the return of a milder air mass, but its duration will be short-lived. Another strong cold front will move across the region Thursday night. In its wake, an unseasonably cold weekend will follow. There is a small chance that a weak system could bring a period of light snow or flurries to parts of the region on Sunday.

First measurable snowfall statistics for select cities:

Allentown: Normal: December 6; 2020-21: December 9
Bridgeport: Normal: December 3; 2020-21: December 16
Islip: Normal: December 10; 2020-21: December 16
New York City: Normal: December 13; 2020-21: December 16
Newark: Normal: December 9; 2020-21: December 9
Philadelphia: Normal: December 19; 2020-21: December 16

The temperature anomaly for November 20-30 is on course to average below normal due to the development of AO blocking. The recent guidance has been correcting colder in response to this blocking. The Arctic Oscillation fell below -1.000 on November 23. Such strong blocking typically favors a period of colder than normal weather (November 20-30, 1991-2020 period):

Boston: Normal: 42.2°; AO cases: 38.4°
New York City: Normal: 45.5°; AO cases: 41.7°
Philadelphia: Normal: 45.4°; AO cases: 41.7°

The duration of the blocking remains uncertain. Should blocking dissipate, warmer conditions could develop near the start of December. Both the CFSv2 and EPS weeklies favor a return of warmer air at some point during the first week of December.

Fall 2021 is well on course to being wetter to much wetter than normal in the northern Middle Atlantic region. Since 1869, there have been 9 August cases where New York City picked up 20.00" or more rainfall during the summer. Two thirds of those cases (and 4/5 of those with summer mean temperatures of 73.0° or above) had 17.00" or more fall precipitation in New York City. 2011 is probably the closest match in terms of precipitation and a nearly identical summer mean temperature. Mean fall precipitation for those 9 cases was 14.86". The median was 17.35". The 1991-2020 normal value is 12.27". Fall rainfall through November 23 4 pm is 16.28".

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.67°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +8.40 today.

The preliminary Arctic Oscillation (AO) figure was -1.410 today.

On November 21 the MJO was in Phase 4 at an amplitude of 1.023 (RMM). The November 20-adjusted amplitude was 1.305 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 95% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 46.4° (1.6° below normal).

 

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Like we are seeing this month, a -WPO and +EPO can average near to below normal. But it all depends on how the other teleconnections line up. It’s  more a back and forth pattern than any record cold. You would want a -EPO for a daily cold record. But smaller cold departures can occur with a well placed -WPO.

 

-WPO +EPO this November 

 

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33 minutes ago, snowman19 said:

As Bluewave pointed out, you know what you are looking at is not -EPO right? A ridge in the Aleutians is -WPO. A ridge over Alaska and the GOA would be -EPO 

We don’t need a -EPO for big nor’easter. There is North Atlantic blocking in place, and the western ridge is centered over WASHINGTON. That tells me that the pattern does not favor these out to sea solutions. There is plenty of room for the northern branch to dig farther south, leading to more amplification, redevelopment of the Miller B farther south, a stronger storm at peak, and a slower moving storm. 

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2 minutes ago, George001 said:

We don’t need a -EPO for big nor’easter. There is North Atlantic blocking in place, and the western ridge is centered over WASHINGTON. That tells me that the pattern does not favor these out to sea solutions. There is plenty of room for the northern branch to dig farther south, leading to more amplification, redevelopment of the Miller B farther south, a stronger storm at peak, and a slower moving storm. 

You're arguing against a point no one made though. 

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A thread for this (part two) is already out there, if you become more confident.  I'm a little hesitant right now...models have bern vacillating, GFS op generally out to seas and I dont have any confidence in the ICON.  Maybe tomorrow morning will show some slight consistency?  I'd like to see the EC have snow for us, 3 consecutive runs.

In any case, the pattern is fairly blocky and good cold for us but whether anything can generate other than a CFP Sunday, am unsure. 

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1 hour ago, George001 said:

We don’t need a -EPO for big nor’easter. There is North Atlantic blocking in place, and the western ridge is centered over WASHINGTON. That tells me that the pattern does not favor these out to sea solutions. There is plenty of room for the northern branch to dig farther south, leading to more amplification, redevelopment of the Miller B farther south, a stronger storm at peak, and a slower moving storm. 

it won't be a noreaster, probably more like a clipper, still it will be our first snow of the season

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2 minutes ago, ForestHillWx said:

29 now.
 

Just had to chase off a decent size black bear with my dog in support from around the chicken coop. I then witnessed an impressive shooting star that looked like it split into fragments. Impressive night so far. 

wow late Leonids?

also, you have a chicken coop lol?

 

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