donsutherland1

There were 3 prior cases: 1881-1882, 1889-1890, 1931-1932. 2023-2024 (34.8° was a near miss). Suburbs are cooler. In the larger picture, I don't think Detroit and its vicinity have any worries that winter will essentially become unrecognizable for decades to come.

The latest CFSv2 SST forecast is showing an outlook that bears some similarity to the Winter 2012-13 anomalies in the Pacific (ENSO Regions northward). Winter 2012-2013 SSTAs: Winter 2012-13 was classified as a neutral-cool winter on ONI, but a La Niña winter on RONI (DJF: -0.62). That's within the realm of plausible scenarios this winter, though I expect the ENSO R3.4 and ONI anomalies to be a bit cooler this time around. Winter 2012-13 was warmer than normal in the eastern half of the U.S., but it wasn't a "blowtorch" winter. The most notable aspects of this winter were a big southern New England snowstorm and seasonal snowfall totals that ranged from much below normal in Washington, DC, somewhat below normal in New York City, and well above normal in Boston. Snowfall totals ranged from below normal in Chicago to near normal in Detroit. October 2012 saw much more widespread cool anomalies than is likely this time around. Finally, the CFSv2 winter temperature forecast differs markedly from the 2012-13 scenario. Models take into consideration far more than SSTs. This is a key point. One should not get caught up with whether there will or won't be a "blob" at this point in time. SSTs can change. Moreover, they are one variable, even if they are important. Finally, the CFSv2's latest forecast is the coolest so far for the Great Lakes into the Northeast. Meanwhile, late summer conditions will prevail today from the Great Lakes region, across southern Ontario and Quebec, into the northeastern United States.

From BLM:

I believe any transition to structurally lower snowfall at Detroit is at least several decades away. 35° or above winter warmth will likely remain very uncommon for at least the next 20 or more years.

Under bright sunshine, much of the region saw temperatures soar into the 80s. Areas immediately on the coastline were a bit cooler. Preliminary highs included: Hartford: 80° Islip: 83° (tied record set in 2023) New York City-Central Park: 82° New York City-LaGuardia Airport: 83° Newark: 87° Poughkeepsie: 82° White Plains: 82° Tomorrow will be another very warm day. Highs will generally reach the upper 70s to lower 80s. A few of the warmest spots will reach the middle and perhaps upper 80s. The warm weather will continue through early next week. Another strong cold front will likely cross the region around midweek. The frontal passage will likely bring some showers or thundershowers. A shot of much cooler air will follow. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -0.5°C for the week centered around September 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.12°C and the ENSO Region 3.4 anomaly has averaged -0.42°C. La Niña conditions will likely develop during mid- or late-autumn. The SOI was +4.64 today. The preliminary Arctic Oscillation (AO) was +1.096 today.

Islip has reached 83°. That ties the daily record set in 2023.

92 is its October monthly record.

He was referring to New York City (Central Park). Interior sections are cooler than NYC's heat island. For example, using the two seasons you cited, the winter mean temperatures were as follows at nearby SMQ: 2017-18: 31.7° and 2020-21: 32.6°. For Central Park, the winter mean temperatures were 36.1° for both winters. Here's how 50" seasons disappear in New York City's historic climate record: Mean Winter Temperature above 32° (qualifying 50" or above seasons are denoted in red): Mean Winter Temperature above 33° (qualifying 50" or above seasons are denoted in red): Mean Winter Temperature above 34° (qualifying 50" or above seasons are denoted in red): New York City (JFK, LaGuardia, and Central Park) has never had a 50" season with a mean winter temperature above 35.0°. In the broader Mid-Atlantic, Washington, DC has a single case at 35.8°, so under the right circumstances, the upper-bound is higher than what New York City's climate record shows. On the issue of a VEI-7 eruption, it would lead to short-lived but rapid global cooling (perhaps several tenths of a degree C). Mid-latitudes would generally see appreciable cooling. Internal variability can still result in sufficiently cold winters, but the kind of cold typically associated with 50" or above snowfall seasons in New York City is decreasing in frequency. Even last winter was at the outer fringes of temperatures consistent with such snowfall in New York City's climate record. Interior sections away from the coast and outside the major heat islands of the big cities remain sufficiently cool for more frequent 50" or above seasons, and they will remain that way for several more decades at a minimum. However,@bluewavewas addressing New York City. He wasn't making an argument outside of New York City.

To illustrate @bluewavepoint about warming winters and reduced frequency of 50” snow seasons in NYC, here’s a chart that depicts winters with mean temperatures below 35 (blue) and 35 or above (red) and seasonal snowfall.

Significant dry conditions (widespread negative Palmer Z-Index anomalies). The greens/blues are dry; the yellows/oranges are wet:

Yes. Values are assigned based on their range. One can manually make adjustments.

Yes.

The shading is based on the historic figures. Next time, I will manually force the same y-axis.

Here you go. Historic: 1869-2025: 2000-2025: Note: October 1-3 goes through 2025 while October 4-31 goes through 2024.

Frequency of 80° or above highs at Central Park: 1869-2025: 2000-2025: Note: October 4-31 is from 1869-2024.

Today got off to another chilly start. Many areas outside New York City again saw the temperature start out in the 40s with colder spots recording 30s. Low temperatures included: Bridgeport: 48° Danbury: 41° Islip: 47° Montgomery: 35° New Haven: 45° New York City-Central Park: 54° New York City-JFK Airport: 51° New York City-LaGuardia Airport: 57° Newark: 51° Poughkeepsie: 39° Sussex: 38° Westhampton: 35° White Plains: 47° In parts of the Upper Midwest and Northern Plains, daily and monthly high temperature records were set. Green Bay (88°) and Rapid City (96°) tied their October monthly records. Philip, SD reached 98°, breaking its October monthly record of 97° for October 1, 1953. The New York City area will be on the fringes of this exceptionally warm air mass this weekend into early next week. A warm weekend lies ahead. Highs will generally reach the upper 70s to lower 80s. The warm weather will continue early next week. Another strong cold front will likely cross the region around midweek. The frontal passage will likely bring some showers or thundershowers. A shot of much cooler air will follow. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -0.5°C for the week centered around September 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.12°C and the ENSO Region 3.4 anomaly has averaged -0.42°C. La Niña conditions will likely develop during mid- or late-autumn. The SOI was +5.48 today. The preliminary Arctic Oscillation (AO) was +0.374 today.

I believe he's describing the declining number of snow days.

Once the winter mean temperature reaches 34.0° or above, the frequency of 50" or above snow seasons largely but not completely disappears. Washington, DC's 35.8° (2009-10) is the single case above 35.0° among all of the listed locations. For Central Park and also additional locations:

Yes, the cold season is being compressed. Lows of 32° or below: Lows < 20°: Highs of 32° or below:

It’s rare in the lower elevations and about a once-every-five-year occurrence in the mountains. Belgrade’s first snowfall is typically November 30 (earliest: October 7, 1897: Trace).

Highly unlikely. Since 1869, only 1891 (October 5) and 2002 (October 7) had the last 70 or above high on or before October 7 at Central Park. Records go back to 1869.

That's not likely to happen for decades. Even if Baltimore sees no snow from winter 2025-26 through 2039-40 (virtually certain not to be the case), the 30-season moving average would be 7.2" vs. the current 18.9" through 2024-2025. Through at least mid-century, there will likely be some snowy winters even as the long-term snowfall average generally declines. Although Washington, DC has likely transitioned into a lower snowfall regime and Baltimore to NYC are likely in the early stages of such a transition, the idea that snowy winters are a thing of the past is not likely to hold true through at least mid-century, if not longer. Such winters will likely grow less frequent as warming continues, but they won't disappear altogether. That outcome might not occur until global temperatures are 3°C above pre-industrial levels, which appears likely in the vicinity of 2100 (maybe a little earlier if some of the positive feedbacks e.g., Arctic cloud changes, etc. lead to a further acceleration in warming). The transition for Baltimore, Philadelphia, and New York City will likely be noisier (bigger rise, greater volatility) and perhaps a bit more extended e.g.. to 37.5° mean winter temperatures than it was for Washington, DC due to their closer proximity to cold source regions.

Unfortunately, the later research has suggested that a higher Siberian Snow Advance Index (SAI) is correlated with a positive AO. The research notes that the early inverse relationship found by Cohen et al., was an exception, not a rule. Excerpts: The running decadal correlations between the SAI_OCT and AO and SAI_NOV and AO are shown in Fig. 7d and e, respectively. In the former, there are significantly more positive than negative values (Table 3), suggesting that the period of strong positive (negative as defined here) correlations that occurred in the 1990s and 2000s, as described by Cohen and Jones (2011), was a rather exceptional event, as previously noted by Peings et al. (2013). Indeed, the frequency of decades with significant SCA_OCT–AO correlations of either sign are not significant. In addition to the recent period in the 2000s, Fig. 7d reveals a period of significant negative correlations centred in the 1840s, also present in the 21-year data (Fig. S4d). Finally, the ERA5 data reveal that the recent period of the statistically significant negative relationship between SAI_OCT and the AO has ended: the most recent decades have positive r values.

Here's how the second half of October has fared after a warmer or colder than normal first half since 1990.

It wouldn't take much in terms of snowfall. I doubt that it will be as cold as last winter. My thinking early on for NYC: +1.0° to +1.5° and 15"-25" snowfall.