donsutherland1

TEMP _________DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA -1.0 -2.0 -2.0 -3.3 2.5 1.6 1.4 1.1 0.1 SNOW _______ DCA _ NYC _ BOS ___ ORD ____DTW ___ BUF __ DEN _ SEA _ BTV 10.0" 20.0" 40.0" 37.5" 45.0" 92.0" 40.0" 6.5" 80.0"

For perspective, no industry comes close to the explicit and implicit subsidies received by the fossil fuel industry. From the IMF:

Some December Snowfall Statistics: For Philadelphia, the December date(s) with the highest frequency of each snowfall threshold is: Measurable snowfall: December 14 and December 29: 15 occurrences 1.0" or more snow: December 5 and December 26: 10 occurrences 6.0" or more snow: December 19 and December 26: 3 occurrences 10.0" or more snow: December 26: 2 occurrences

The 11/30 0z and 6z GEFS has returned to a warmer outlook for much of North America after December 10th. It offers a credible alternative scenario. I'm still going with the EPS/ECMWF weeklies, as the GEFS has shown inconsistency. Moreover, the size of the rebound in temperatures (December 11-20 vs. December 1-10) would be both extreme and rare. Nevertheless, a look at the alternative scenario is still in order as a muted variation is plausible. The GEFS's development of a fairly strong PNA- is the key variable differentiating it from the colder baseline idea shown on the EPS. The latest two cycles of the GEFS show the development of a WPO-/EPO+/AO-/PNA- pattern. The GEFS maps are consistent with the largest cluster for the December 5-15 period (39%) of cases. WPO-/EPO+/AO-/PNA- Maps (Largest December 5-15 cluster): 500 mb Height Anomalies: Temperature Anomalies: GEFS (11/30 6z cycle): Days 11-15: 500 mb Height Anomalies (5-day average): Temperature anomalies (5-day average):

Central Park's frequency of measurable snowfall in December and record daily snowfall. December 26 is New York City's snowiest December date. Frequency of select daily snowfall amounts (1869-2024): Measurable snowfall: 22 times 1" or more: 16 times 6" or more: 5 times 10" or more: 5 times

From Iowa:

So far, 5"-7" of snow has fallen in the greater Chicago area. Daily snowfall records for November 29th have fallen in both Rockford and Chicago. The snowstorm will continue to blanket parts of the Great Lakes Region tonight into early tomorrow. Chicago and Milwaukee will likey see 6"-12" of snow. Some locally higher amounts are possible. Detroit could pick up 4"-8". Toronto could see 3"-6". In the New York City area, tomorrow and Monday will be somewhat milder. Showers are possible on Monday as a cold front moves across the region. Generally colder than normal conditions could then continue into or through the second week of December. Severe cold appears unlikely through at least the first 10 days of December. Nevertheless, December 1-10 will be a solidly colder than normal period. Moreover, a storm could affect the region on Tuesday into Wednesday, bringing 0.50"-1.50" precipitation to the region. There is a distinct possibility that New York City could see its first measurable snowfall of the season. Interior sections have the highest probability of seeing accumulations of snow. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -3.95 today. The preliminary Arctic Oscillation (AO) was -0.264 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 47.2° (0.8° below normal). Supplemental Information: The projected mean would be 0.5° below the 1981-2010 normal monthly value.

As of 1 pm CST, Chicago (3.2") and Rockford (3.2") had set new daily snowfall records for November 29. Chicago's old mark of 3.0" was set in 1942. Rockford's old record of 3.0" was set in 1925. Upstream, parts of Iowa had seen 12" of snow.

I'm in briefly. I checked. Here are the December composites (1980-2024) for EPO+/PNA+/AO-/NAO- 500 mb Height Anomalies: Temperature Anomalies: Precipitation Rate: n=121 dates I suspect that there's a lot of variability, though.

I will check when I get home this evening.

As of 7 am, Chicago had picked up 0.5" of snow. Rockford had received 1.0". The highest amounts were at Chatsworth (3.0") and Melvin (2.0").

Parts of the region saw some heavier snow showers yesterday. Binghamton wound up picking up 1.6". Even heavier snow fell in some of the lake effect areas. Syracuse picked up 10.3" of snow, breaking the daily record of 8.8" from 1958.

The snow is sticking in Chicago. Courtesy of EarthCam:

Central Park has recorded its first freeze of the 2025-2026 season. The 1991-2020 normal first date is November 21. The 1961-1990 baseline was November 11. Last winter's first freeze occurred on November 30.

Tomorrow will be unseasonably cold. There is potential for New York City's Central Park to experience its first freeze of 2025 tomorrow morning. The 1991-2020 normal first date is November 21. The 1961-1990 baseline was November 11. Last winter's first freeze occurred on November 30. Saturday and Sunday will see a snowstorm blanket parts of the Great Lakes Region. Chicago and Milwaukee could see 6"-12" of snow. Detroit could pick up 4"-8". Toronto could see 3"-6". Sunday and Monday will be somewhat milder. Showers are possible on Monday as a cold front moves across the region. Generally colder than normal conditions could then continue into or through the second week of December. Severe cold appears unlikely through at least the first 10 days of December. Nevertheless, December 1-10 will be a solidly colder than normal period. Moreover, a storm could affect the region on Tuesday into Wednesday, bringing 0.50"-1.50" precipitation to the region. There is a distinct possibility that New York City could see its first measurable snowfall of the season. Interior sections have the highest probability of seeing accumulations of snow. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -3.12 today. The preliminary Arctic Oscillation (AO) was +0.081 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 47.2° (0.8° below normal). Supplemental Information: The projected mean would be 0.5° below the 1981-2010 normal monthly value.

There was a heavier snow shower in the Harriman, NY area this afternoon.

The latest HREF output:

2009-10 was a strong El Niño. 2010-11 was a strong La Niña.

Yesterday, I noted that the GEFS was trying to push an EPO+, but its forecast 500 mb pattern was profoundly different from any of the December WPO-/EPO+/AO-/PNA- clusters. That suggested that either the teleconnection idea was off or the pattern was off, rather than some novel outcome. Overnight and through today's 6z cycle, the GEFS has continued to evolve. It has added a WPO+ to its EPO+ idea and restored its earlier idea of a AO+. It has now joined the Canadian ensembles that keep the MJO out of Phase 8 through its forecast horizon. In short, its previously significant areas of "disconnect" have disappeared overnight. Its forecast pattern is now more consistent with what one would expect. For now, the GEFS is trying to build a credible milder alternative scenario for the pattern/temperature evolution in North America toward mid-December. The EPS has not shifted toward that emerging GEFS idea. Therefore, the baseline idea remains that the northern tier of the U.S. and most of Canada should remain cold toward and probably beyond mid-December. The Southeast could still turn warm despite some shots of colder air. Mid-December and beyond is still in the low-skill distant realm. The big story through the weekend will be the significant snowstorm that will affect parts of the Midwest and Great Lakes Region. As a result, Chicago, Detroit, Milwaukee, and Toronto remain on track to experience their snowiest fall in five or more years. As an appetizer, Detroit added 0.1" snowfall yesterday and Toronto picked up 1.2 cm (0.5") yesterday.

Tomorrow and Saturday will be unseasonably cold days. Tomorrow will be windy with a possibility of some snow flurries. There is potential for New York City's Central Park to experience its first freeze of 2025 tomorrow or, more likely, Saturday morning. The 1991-2020 normal first date is November 21. The 1961-1990 baseline was November 11. Last winter's first freeze occurred on November 30. Saturday and Sunday will see a snowstorm blanket parts of the Great Lakes Region. Chicago and Milwaukee could see 6"-12" of snow. Detroit could pick up 4"-8". Toronto could see 3"-6". Sunday and Monday will turn somewhat milder. Showers are possible on Monday as a cold front moves across the region. Generally colder than normal conditions could then continue into or through the second week of December. Severe cold appears unlikely through at least the first 10 days of December. Moreover, a storm could affect the region on Tuesday into Wednesday, bringing 0.50"-1.50" precipitation to the region. There is a distinct possibility that New York City could see its first measurable snowfall of the season. Interior sections have the highest probability of seeing accumulations of snow. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was +1.97 today. The preliminary Arctic Oscillation (AO) was +0.036 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 96% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 47.1° (0.9° below normal). Supplemental Information: The projected mean would be 0.6° below the 1981-2010 normal monthly value.

For reference: The 33.5 cm snowfall at Toronto on November 30, 1940 is the biggest daily snowfall on record for November. The 10.0" for Milwaukee on November 30, 1940 is the second biggest daily snowfall on record for November.

I'm not that surprised. The 11/27 0z cycle reflects yesterday's development where the GEFS backed off its development of a pronounced AO+ pattern. It is trying to push an EPO+, but its 500 mb pattern is profoundly different from any of the December WPO-/EPO+/AO-/PNA- clusters. Assuming that the simplest explanation is more likely, the pattern disconnect from its forecast teleconnections suggests that either the teleconnection idea is off or the pattern is off, rather than some novel outcome. The pattern closely resembles the EPS, which does not show an EPO+ pattern. Thus, I suspect that the EPS has a better handle on the overall pattern right now. The northern tier of the U.S. and most of Canada should remain cold toward and probably beyond mid-month if that holds. Unfortunately, the SE could still turn warm despite some shots of colder air.

The pattern evolution for the opening 10 days of December still looks very good. With respect to the December 11-25 period, the guidance has shifted. For a time, the GEFS was showing the development of a pronounced AO+ pattern. Now, it has backed off (12z and 18z cycles). As a consequence, the baseline Scenario 1 still seems to be the best one going forward, while recognizing that there is some risk of a break near mid-month. The latest ECMWF weekly forecast largely maintains the sensible weather effects from Scenario 1. Given the shifting of the guidance, it makes sense to continue to monitor the teleconnections (and other factors) while reserving judgment for changes until later to avoid making changes based more on model noise than actual developments. Milwaukee, Chicago, Detroit, and Toronto remain in line for a snowstorm during the November 29-30 period. Significant snow is possible in Milwaukee and Chicago. A moderate snowfall looks reasonable for both Detroit and Toronto. Changes can still occur. WPC is now showing a 70% chance of a moderate winter storm impact in Chicago and surrounding areas for the 24-hour period ending November 30 7 am. Chicago remains on course to experience its snowiest fall since 2019 (8.3") and possibly even 2018 (12.7"). Milwaukee should see its snowiest fall since 2019 (13.4"). Detroit will likely experience its snowiest fall since 2021 (7.1") and possibly 2019 (9.5"). Toronto could see its snowiest fall since 2020 (23.4 cm/9.2") and perhaps 2002 (27.2 cm/10.7"). Fall 2025 Snowfall Totals (through November 26): Chicago: 1.7" Detroit: 2.2" Milwaukee: 0.6" Toronto: 12.8 cm (5.0")

In the wake of the storm that brought rain to the region last night into early today, colder air will rush into the region tonight. The closing days of November will be much colder. There is potential for New York City's Central Park to experience its first freeze of 2025. The 1991-2020 normal first data is November 21. The 1961-1990 baseline was November 11. Last winter's first freeze occurred on November 30. The opening days of December will turn somewhat milder. However, colder conditions could begin to develop during the second half of that week and then continue into or through the second week of December. Severe cold appears unlikely through at least the first 10 days of December. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was +20.23 today. The preliminary Arctic Oscillation (AO) was -0.232 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 94% probability that New York City will have a cooler than normal November (1991-2020 normal). November will likely finish with a mean temperature near 46.9° (1.1° below normal). Supplemental Information: The projected mean would be 0.8° below the 1981-2010 normal monthly value.