December 2025 OBS and Discussion

[bluewave]

2 minutes ago, brooklynwx99 said:

if you retro that Pacific trough a bit more and allow for the ridge axis over the Plain to shift 100mi towards Montana, things become very interesting 

Yeah, we would want the ridge in a similar position to what we got with the recent clipper to make things interesting. I am just not sure yet whether the Pacific Jet can relax enough to allow for sufficient retrogression. The time to watch would probably be early in January.

 

[snowman19]

9 minutes ago, bluewave said:

 

This is going to be one of the strongest -WPO blocks that we have seen for the month of December.

But it’s a different configuration of other factors that we have previously seen with December -WPOs in the past.

This one has a much more amplified Pacific Jet into the PACNW and BC than we have seen before with the historic flooding in those areas. Plus we have an out of phase +EPO and very strong ridge onto the Western US. 
 

Unique December 2025 500 mb and Pacific Jet stream pattern compared to previous very strong -WPO patterns

 

 

Chris, are there even any analogs for what the models are projecting for next week into the first few days of January? It’s extremely anomalous like you said…huge Aleutian ridge (-WPO), out of phase +EPO, strong -PNA, -NAO, neutral/negative AO and a massive omega ridge/omega block dead center of the CONUS?

[EasternLI]

18 minutes ago, brooklynwx99 said:

if you retro that Pacific trough a bit more and allow for the ridge axis over the Plain to shift 100mi towards Montana, things become very interesting 

Might be doable. Previous runs had that ridge centered more in Iowa. It's already ticked west a little bit. Maybe that continues. 

[jm1220]

5 hours ago, NorthShoreWx said:

Heads up, there's black ice out there right now.   Be wary on the roads.

Yep, ice everywhere this morning. 

[MJO812]

Nice

[EastonSN+]

Definitely good trends overnight with a stronger NAO block. The operational models also hint at a coastal, albeit for areas south of us right now.

[The 4 Seasons]

First season to date snowfall maps. This is as of December 17th, 2025. Reports are from cocorahs, COOP, and official climo sites. Contours are based on these reports and NOHRSC Gridded Snowfall Analysis. These are by far the hardest maps to put together so ill be doing them monthly similar to last season. 

[EastonSN+]

1 minute ago, EastonSN+ said:

NOT hinting that this will happen, however, the setup COULD yield a storm like this. The storm tries to cut through New England however the blocking forces the storm just south.

 

 

[bluewave]

10 minutes ago, The 4 Seasons said:

First season to date snowfall maps. This is as of December 17th, 2025. Reports are from cocorahs, COOP, and official climo sites. Contours are based on these reports and NOHRSC Gridded Snowfall Analysis. These are by far the hardest maps to put together so I’llbe doing them monthly similar to last season. 

Very nice job. Can’t say I remember seeing this accumulation pattern before from a clipper. I didn’t notice any available models showing the NW heavy snow band from Sussex into Orange and surrounding areas. 

[EastonSN+]

13 minutes ago, The 4 Seasons said:

First season to date snowfall maps. This is as of December 17th, 2025. Reports are from cocorahs, COOP, and official climo sites. Contours are based on these reports and NOHRSC Gridded Snowfall Analysis. These are by far the hardest maps to put together so ill be doing them monthly similar to last season. 

As usual great work and thanks again.

Central park and LGA amounts stick out like a sore thumb lol. 

[SACRUS]

26 / 25 and on the way to (for some) the months warmest highs in the mid / upper 40s, perhaps some of the warmest get to 50.  Rain by the morning Friday and a warm Southerly flow gets most into the mid 50s and some to 60, with around an inch of rain.  Colder Saturday starts a bit of a back and froth colder - Sat, warmer - Sun ,   colder - Mon /Tue.  Then warmer overall by Christmas through around the 29th/30th with the eneext storm threat in the 30-31 period.  Ridge builds in the center with the cold just into the northeast which means a day or two very warm in the period and some quick pull back colder.  Beyond there looks near normal.

 

[SACRUS]

Records:

Highs:

EWR: 64 (2023)
NYC: 63 (1984)
LGA: 63 (2023)
JFK: 64 (1984)

Lows:

EWR: 13 (1953)
NYC: -1 (1919)
LGA: 16 (1953)
JFK: 16 (1973)

Historical:

1620: The Pilgrims landed at Plymouth, MA in a severe windstorm. (Ref. Wilson Wx. History)

1779: The first big snowstorm of the "hard winter" dumped 17 inches on New Haven, CT. (Ref. Wilson Wx. History)

1919: New York, New York: The Central Park temperature drops to one degree below zero F, the earliest sub-zero temperature in the city on record. A cold air mass brought record cold along the east coast.
Other daily record lows for the date included: Burlington, VT: -13 °F, Syracuse, NY: -13 °F, Worcester, MA: -11 °F, Portland, ME: -10 °F, Rochester, NY: -7 °F, Boston, MA: -6 °F, Hartford, CT: -6 °F, Elkins, WV: -5 °F, New York (Central Park), NY: -1 °F, Philadelphia, PA: 4 °F, Baltimore, MD: 7 °F and Washington, DC: 10 °F. (Ref. Wilson - Additional Temperatures Listed On This Link)

1944: The powerful U.S. Third Fleet was still in the grips of powerful Typhoon Cobra December 17th and 18th. The encounter with the typhoon was more damaging to the Fleet than many battles with the Japanese.
(Ref. Wilson Wx. History)
 

1957 - A tornado swept across Jackson County, Williamson County and Franklin County in southern Illinois killing eleven persons. (David Ludlum)

1981 - A heavy lake-effect snow blanketed the southern and southeast shores of Lake Michigan leaving up to 22 inches of snow at Valparaiso IND. (David Ludlum)

1983 - Record cold hit the north central states. At Havre, MT, the mercury plunged to a record reading of 34 degrees below zero. (Sandra and TI Richard Sanders - 1987)

1984 - A storm over southern California left up to 16 inches of snow in the mountains and upper deserts, with 13 inches reported at Lancaster. Edwards Air Force Base was closed, and Interstate 5 was closed from Castaic to the Tehachapis Mountains. (18th-19th) (The Weather Channel)

1986 - A strong winter storm, which developed off the coast of New Jersey and moved out to sea, lashed the northeastern U.S. with high winds, heavy rain, and heavy snow. The storm left snowfall amounts of up to 30 inches in Vermont, 24 inches in Massachusetts, and 20 inches in New Hampshire. The highest rainfall amounts approached four inches in southern New England, where winds gusted to 70 mph. (Storm Data)

1987 - A weakening storm moved into the Rocky Mountain Region producing six inches of snow at the Platoro Reservoir in the San Juan Mountains of Colorado. The storm then spread rain and drizzle across the Southern High Plains into the Middle Mississippi Valley, with thunderstorms over Texas. (Storm Data) (The National Weather Summary)

1988 - Warm weather prevailed in the central U.S. while cool weather prevailed across the eastern states. Sheridan, WY, with a record warm afternoon high of 68 degrees, was seven degrees warmer than Key West FL. (The National Weather Summary)

1989 - A winter storm moving out of the Great Plains Region spread freezing rain, sleet and snow across parts of the southeastern U.S. Freezing rain resulted in 170 auto accidents in the Memphis area during the evening hours. Unseasonably warm weather continued ahead of arctic cold front. Miami FL equalled their record for December with an afternoon high of 87 degrees. (Storm Data) (The National Weather Summary)

1998: Atlanta, GA recorded its latest first freeze on record while across the southwest desert, Palm Springs, CA set a record high with 86 °F. (Ref. Wilson Wx. History)

2006: High pressure off the Carolina coast, combined with strong upper level high pressure over the Yucatan Peninsula and a strong trough out west produced a warm southwest flow resulting in record high temperatures from the Mississippi Valley to New York State including: San Antonio, TX: 81 °F-Tied, Mobile, AL: 77 °F-Tied, Charleston, SC: 77 °F-Tied, Sterling (Dulles Airport), VA: 76 °F, Greenville-Spartanburg, SC: 76 °F-Tied, Richmond, VA: 75 °F-Tied, Washington, DC: 74 °F, Tupelo, MS: 74 °F-Tied, Chattanooga, TN: 73 °F, Baltimore, MD: 72 °F, Nashville, TN: 72 °F, Wilmington, DE: 71 °F, Atlantic City, NJ: 71 °F. (Ref. Wilson - Additional Temperatures Listed On This Link)
 

2009 - A monster snow storm affected the Mid-Atlantic and Northeast regions of the U.S. on December 18th through December 20th. The storm originated in the Gulf of Mexico and moved northward along the Eastern Seaboard, leaving behind heavy snow accumulations from North Carolina to Massachusetts. Impacts from this storm included the closing of major airports, interstate highways, and rail systems. Over 1,200 flights were cancelled at the three major airports in the New York City area, and hundreds of thousands of people lost power due to the storm. Seven people were reported killed across the Mid-Atlantic (source: Reuters). Over two feet of snow accumulation was reported in portions of North Carolina, Virginia, West Virginia, Maryland, New Jersey, and New York. At one point, the storm was over 500 miles in width, and affected 14 states and tens of millions of Americans (Source: AFP).

[forkyfork]

not bad

[snowman19]

10 minutes ago, bluewave said:

The 500 mb analogs composite has the ridge axis a little further East. Probably related to how anomalous the ridge is centered just to west . It’s shifting eastward from where it has been in the West for the first part of month.

 

Especially given the -PNA and the very amplified PAC jet crashing into the PAC NW, that would make sense (omega ridge rolled over further east from the dead center of the CONUS position) that the models show right now

[bluewave]

4 minutes ago, snowman19 said:

Especially given the -PNA and the very amplified PAC jet crashing into the PAC NW, that would make sense (omega ridge rolled over further east from the dead center of the CONUS position) that the models show right now

This will be a good test for the AIFS EPS coming up since it matches the composite more than the EPS with the further east ridge axis.

 

 

[SACRUS]

 

GFS is further expansive east with the ridge and the Euro had a cutoff building NE to SW in the Dec 30 period.

 

[SACRUS]

 

Looks like NYC was at 0 departure on Wed and the below streak stopped at 20,  EWR and other sites were still below yesterday.  Today that will bring the below daily departure streak to an end at 20-21 days.  

[SACRUS]

 

Oddly with enough warmth tomorrow - we could see or approach record highs (EWR-60 / NYC - 58)

[The 4 Seasons]

1 hour ago, bluewave said:

Very nice job. Can’t say I remember seeing this accumulation pattern before from a clipper. I didn’t notice any available models showing the NW heavy snow band from Sussex into Orange and surrounding areas. 

Nope and thats where we blew the forecast pretty hard. i had 1-2/2-4 in areas that picked up over 6. Everywhere else the forecast did pretty well though

[MJO812]

1 hour ago, forkyfork said:

not bad

Negative NAO doing its work