donsutherland1

I bleieve @Dark Star posts the triangle. His visualization really summarizes things quite well.

My thoughts haven't changed too much overnight. Cooler air arrived a few hours more slowly than had been modeled overnight. But overall, things remain on track for a frigid start to the weekend and a large storm on Sunday into early Monday. The overnight guidance reached consensus that the snow that arrives on Sunday will eventually change to sleet in much of the New York City area and its nearby suburbs. A few of the models cut back on QPF. Almost 95% of EPS and GEFS members show 6" or more snow in New York City. In the bigger picture, the New York City area remains in line for its biggest snowstorm in nearly four or five years. It remains likely that New York City and nearby areas will see a storm total of 6"-12" of snow and sleet. Areas to the south and east of New York City could see 4"-8" amounts. Pockets of 12"-18" amounts are possible well north and west of New York City, most likely in parts of northeastern Pennsylvania, Orange County, Dutchess County, and Sussex County. There remains some uncertainty concerning mid-level and surface storm evolution and tracks, and perhaps somewhat greater uncertainty regarding a potential primary-secondary storm handoff. Model skill will improve markedly today. Whether or not changes will need to be made remain to be seen.

Why? Even areas with warmer climates can see big snowstorms. The NYC area will continue to see periodic big snowstorms and snowy winters for the foreseeable future.

So far, the early 0z guidance has been more about confirming the idea that the snow will transition to sleet in parts of the New York City area (including the City and nearby suburbs) than changing storm total snowfall amounts. QPF has ticked higher. All in all, it hasn't been a bad start to the 0z cycle.

Here's their latest AFD: As strong high pressure retreats to the NE late Sat night into Sunday, an expansive winter storm will impact the area from then into Mon. Primary low pressure moving into the TN valley on Sunday should dissipate while a secondary low forms near Cape Hatteras and the VA capes, and then moves to a position just inside the 40N/70W benchmark. Snow should begin in the NYC metro area after midnight Sat night and spread NE to the rest of the CWA by daybreak, with some accumulation of 1-2 inches possible by daybreak for the NYC metro area. Heavy snow is then likely daytime Sunday into Sunday evening via strong front-end H7-8 frontogenetic and thermal forcing aided by an anticyclonic upper jet to the north. Given the cold air mass in place, snow ratios look to be on the high side (15:1) at the onset, and then settle down a little closer to 12:1 as heavier precip arrives and the low to mid levels slowly warm. Depending on the ultimate track of the system, it remains possible enough warm air could intrude aloft to force a brief mix with sleet and/or freezing rain Sunday night, especially for NYC and Long Island. Have only mentioned a slight chance of this occurring, and at any rate the damage will have been done well before then as far as meeting 6+ inch snowfall amounts. Total QPF for the event should be roughly between 1.0-1.5 inches. Watch mentions potential for at least 6-12 inches with potential for 12 or more inches. The above QPF with higher snow ratios yields widespread potential accumulations of over a foot. As the coastal system exits north and east into Monday, the deepening low and an inverted surface trough may allow for some additional light accumulation much of the day as well, though heavy snowfall should be over by that point.

These are the NWS maps from this afternoon/evening:

From the list of snowstorms I provided earlier, I checked Islip's climate record. Islip's record covers all the snowstorms beginning with the January 1964 blizzard. Only the January 29-31, 1966 blizzard brought less than 6" to Islip (5.0"). My current thinking is that Islip will see 4"-8", but we'll see if that holds up.

You are correct. I accidentally referred to five years ago pertaining to NYC (January 30-February 4, 2021 snowstorm that brought 17.4" to NYC).

Thank you for sharing your memories. May your father RIP. I miss my father, too. He passed away almost 12 years ago.

The upcoming snowstorm will likely join a relatively small number of storms that brought 6" or more to all of the following cities: Baltimore, Boston, New York, Philadelphia, and Washington, DC. Many of those prior storms were epic storms. The list since 1950 is below. In short, not only will this storm likely be New York City's biggest snowstorm in nearly four or five years, it could be a really special event, too.

Get well soon.

Although these maps sometimes overstate snowfall by a category, the below map illustrates just how expansive the impacts of the storm that will ultimately bring the Northeast its biggest snowfall in perhaps nearly five years will be.

From WPC: Probability of overall major storm impact: Probability of major snowfall amount:

Decades? The record-setting January 22-23, 2016 blizzard was just over 10 years ago. The long-duration January 31-February 4, 2021 storm that brought 17.4" to NYC was just under 5 years ago. The Post would do well to consult weather information before writing its headlines.

The concern was whether the storm would miss to the East, not p-types. AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 634 PM EST FRI DEC 24 2010 .LONG TERM /SUNDAY THROUGH FRIDAY/... PLENTY OF UNCERTAINTY ON DETAILS WITH THE STORM PROGGED TO DEVELOP OFF THE SOUTHEAST COAST SATURDAY NIGHT AND INTENSIFY AS IT MOVES EAST OF THE MID ATLANTIC AND NEW ENGLAND COASTS SUNDAY INTO SUNDAY NIGHT...WITH MODELS STILL STRUGGLING WITH PHASING DETAILS OF MULTIPLE SHORTWAVES AS THEY COMBINE TO CARVE OUT A DEEP CLOSED LOW BY SUNDAY...WITH A FULL SPECTRUM OF OUTCOMES RANGING FROM LITTLE OR NO PRECIP TO A MAJOR WINTER STORM. THE 12Z GFS...WHILE LOOKING MOST OMINOUS...WAS NOT FULLY ACCEPTED MAINLY DUE TO INITIALIZATION PROBLEMS WITH UPSTREAM MID LEVEL DISTURBANCES EXTENDING FROM CENTRAL CANADA INTO THE NORTHERN PLAINS...WHOSE INTERACTION WILL IN TURN GREATLY INFLUENCE THE EVOLUTION OF THE COASTAL STORM. THE 12Z ECMWF INITIALIZED THESE FEATURES A LITTLE BETTER BUT STILL NOT PERFECTLY...AND ITS SFC LOW TRACK SUNDAY NIGHT INTO MONDAY...WHILE RIDING A STRONG LOW LEVEL BAROCLINIC ZONE...STILL LOOKS A LITTLE TOO FAR EAST GIVEN THE STRONGER MID LEVEL FORCING LOCATED TO THE WEST. AS A RESULT...THE MOST LIKELY OUTCOME AND COURSE OF LEAST REGRET IS EITHER STRAIGHT CONTINUITY FROM THE PREVIOUS FORECAST...OR A BLEND OF THE 06Z GFS AND 00Z ECMWF...WITH A LOW TRACK CLOSE ENOUGH TO DELIVER ADVISORY CRITERIA SNOWS TO SOUTHEAST CT AND EASTERN LONG ISLAND...LESSER AMOUNTS WESTWARD TO SW CT AND NYC METRO...AND LITTLE IF ANY ACCUMULATION WELL NORTH AND WEST OF NYC. IT SHOULD BE NOTED THAT THE PROBABILITY OF A SIGNIFICANT SNOWSTORM WITH AMOUNTS OVER 6 INCHES IS STILL NONZERO BUT IS LOW...ONLY 30-40 PERCENT FOR EASTERNMOST CT/LONG ISLAND...AND 10-20 PERCENT FARTHER WEST. FORECAST DETAILS MAY STILL BE SUBJECT TO SIGNIFICANT CHANGES IN EITHER DIRECTION AS CONFIDENCE IN THE INTERACTION OF THE MULTIPLE SHORTWAVES TO FORM THIS SYSTEM INCREASES...

With most of the 18z guidance now in, I have no changes from my thinking following the 12z model cycle. In general, the New York City area remains in line for its biggest snowstorm in nearly four or five years. Moreover, the storm will likely reach at least Category 3 on the Northeast Snowfall Impact Scale (NESIS). Further, this could become the first storm since the January 22-24, 2016 blizzard to bring 6" or more snow to all of the following cities: Boston, Baltimore, New York, Philadelphia, and Washington, DC. it appears that a good initial estimate for storm total snow and sleet in New York City and nearby areas will fall in the 6"-12" range. Areas to the south and east of New York City and its nearby suburbs could see 4"-8" amounts. Pockets of 12"-18" amounts are possible well north and west of New York City, most likely in parts of northeastern Pennsylvania, Orange County, Dutchess County, and Sussex County. A reasonable floor for New York City is 5". A reasonable ceiling is 14". There remains a degree of uncertainty concerning mid-level and surface storm evolution and tracks, and a potential primary-secondary storm handoff. Model skill will improve markedly overnight and tomorrow. At that time, there should be convergence toward a consensus among the models. Estimates could be revised based on the subsequent guidance, as needed.

Arctic air is poised to return to the area tomorrow. A frigid weekend lies ahead. That will set the stage for the region's biggest snowstorm so far this winter and perhaps in a number of years. The temperature will likely stay below 20° in New York City and much of the region on Saturday. The last time that happened in New York City was January 21, 2025 when the high was 19°. Snow could arrive on Sunday. A significant snowfall is likely in and around the New York City area and surrounding region, even as a transition to sleet is likely. At present, it appears that New York City and its nearby suburbs are in line for 6"-12" of snow. Higher amounts are likely north and west of the City where ratios will be higher and mixing is less likely. There could be a few pockets of 12"-18" amounts in that region. Lesser amounts, probably in the 4"-8" range appear likely along the central Jersey Shore and across parts of Long Island. The last time New York City saw a 6" or greater snowfall was January 28-29, 2022 when 8.3" fell. Its last 10" or above snowfall occurred during January 31-February 3, 2021 when 17.4" accumulated. There remains uncertainty and it may still be another day or two before the details can be pinned down with high confidence. Very cold air will return to the region as the storm departs. Highs will be in the 20s through at least midweek. Overall, January 20th-February 3rd will likely be the coldest and perhaps snowiest two-week period this winter. The forecast WPO-/EPO-/AO-/PNA+ pattern is typically the coldest pattern in January and among the coldest during the first half of February. A persistently positive PNA will have above climatological risk of moderate or significant snowfalls. For perspective, the coldest two-week period this winter prior to January 20th was January 3-16, 2026 and January 4-17, 2026 with a mean temperature of 30.3°. The snowiest two-week period was December 14-27, 2025 when 7.2" of snow fell. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -0.7°C for the week centered around January 14. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.48°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions will likely continue into at least late winter. The SOI was -4.52 today. The preliminary Arctic Oscillation (AO) was -2.162 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 98% probability that New York City will have a cooler than normal January (1991-2020 normal). January will likely finish with a mean temperature near 30.6° (3.1° below normal). Supplemental Information: The projected mean would be 2.0° below the 1981-2010 normal monthly value.

That's from NWS New York's Area Forecast Discussion.

https://www.weather.gov/okx/winter

One possible difference of note is that NWS Upton referred to NBM v.5.0 (this is the parallel version that is being tested and will be implemented during the spring) while NWS Mount Holly referenced DESI. DESI uses v4.2. The experimental version has more conservative snow-liquid ratios.

As for the medium-term, I have no change in my thinking from Monday that the WPO-/EPO-/AO-/PNA+ pattern will likely be the biggest driver of North American weather conditions through the remainder of January. That pattern is typically the coldest January pattern for the eastern half or third of the U.S., along with at least southern Ontario and Quebec. One or more lows in the single digits and one or more highs in the teens is possible in New York City. Subzero cold is likely in places like Chicago, Detroit, and Toronto. The predominantly positive PNA comes with a heightened risk, relative to climatology, of moderate or significant snowstorms for the East Coast. With the PNA likely to be mainly positive into or through at least the first week of February, it is likely that at least one or more of the following cities will see at least one 6" or above snowstorm from the remainder of January through the first week of February: Baltimore, Boston, New York, Philadelphia, Richmond, and Washington, DC. The only update is that the ECMWF weeklies have grown colder in the Eastern U.S. through much of February. And the kind of pattern in place is often slow to break down. After mid-February, a PNA- is a better setup for East Coast snowstorms, as wave lengths typically grow shorter.

I suspect most of the discussion is currently occurring in the subforums where a significant-major winter storm is forthcoming.

Monday morning with maybe some snow showers into the afternoon. There are differences on the guidance and those details will become clearer in subsequent model cycles.

My thinking about an upcoming significant snowfall in and around New York City remains intact following the 1/22 12z model cycle. Overall, the City remains on course to see its biggest snowstorm in nearly four or five years. The storm will likely attain a Category 3 or, less likely but still possible, Category 4 rank on the Northeast Snowfall Impact Scale (NESIS). NESIS is based on a combination of the area affected by the storm, population in the affected areas, and snowfall amounts. During the height of the storm, the dedridritic growth zone (DGZ) will have temperatures between -17°C and -12°C as per the soundings from multiple models, which is close to ideal for snow growth. The layers below it will be well-saturated, and surface temperatures will be very cold, reducing the risk of melting/riming. As a result, well-accumulating dendrites will be the predominant snowflake. Ratios during this time will probably range from 12:1 to 15:1. A classic paper can be found here: https://www.wpc.ncep.noaa.gov/research/snow2a/snow2a.pdf Later on, warmer air will push into the mid levels (mainly between 650 mb and 800 mb), which will lead to a transition to lower ratios and then sleet for parts of the New York City area, including the City and nearby suburbs. There's a small chance that the storm could end as some freezing drizzle as it pulls away early Monday. Taking into consideration the DGZ conditions, historic data for snowstorms with 1" or greater QPF, the various 12z model solutions, it appears that a good initial estimate for storm total snow and sleet in New York City and nearby areas will fall in the 6"-12" range. Areas to the south and east of New York City and its nearby suburbs could see 4"-8" amounts. Areas with 12"-18" are possible well north and west of New York City, most likely in parts of northeastern Pennsylvania, Orange County, Dutchess County, and Sussex County. A reasonable floor for New York City is 5". A reasonable ceiling is 14". There remains a degree of uncertainty concerning mid-level and surface storm evolution and tracks, and a potential primary-secondary storm handoff. Model skill will improve markedly within another day. Estimates could be revised based on the subsequent guidance, as needed, but the initial estimate is probably a reasonable starting point. Areas north and west of New York City where ratios could be higher for a longer period of time and mixing could be less of an issue, will likely see higher amounts than New York City.

The sounding at 84 hours.