Roger Smith

Tracking anomalies and projected end of month ... _____________________________ DCA _NYC _BOS __ORD _ATL _IAH ___DEN _PHX _SEA _____ (anom 1-16) __________ -9.2 _ -8.7 _ -7.7 __-10.7 _-4.9 _-3.2 __+8.3 _ +5.1 _ +6.4 _____ (p anom 1-31) ________ -5.0 _ -4.5 _ -4.0 __-6.0 _-2.5 _-1.0 __+6.0 _ +3.5 _ +2.5 (17th) _ A more variable regime will cut into large negative anomalies in eastern and central regions. It will stay generally mild in the western regions but SEA will have a larger reversal as arctic air builds in for a while later in the month.

Strong winds also up here, with resultant power failure after trees came down on power lines. Near blizzard conditions in southern Alberta, major highway multi-vehicle pile up north of Calgary. We have lost our thin snow cover during recent mild spell, quite cold in the wind but it cleared up shortly after a couple of brief flurries, still quite windy, 35 F.

Until you see a temp above 47 F, Dec 2025 remains tied with 1917 in first place for lowest max. Sadly that probably won't survive. Today's departure looks like it could push the running anomaly down to around -9 F which will perhaps be the low point for the month. As I was saying yesterday, lots of ups and downs ahead and I would expect this anomaly to be cut in half but -5 to -6 for the month is still possible if there's enough cold in the mix. If the mean after today drops to 32.4 F it will currently be tied with three t-28th coldest Decembers (for the entire month), a finish closer to 36 F seems likely, and the median of all 157 (if below 36.5) will be 36.5 F so there is some chance of the month being in the lower half of all Decembers, something that only happens two or three times a year in the modern and urban-warmed climate. A total of 26 Decembers had a mean at or below 32.0, the only recent ones being 1989 and 2000. By decades it is fairly easy to see the warming of the climate but about half of this is likely due to urban heat island increases. (27th was 1892 at 32.2 and the three at t-28th 32.4 are 1909, 1944 and 1995). Three more (1902, 1921, 1980) were tied at 32.5 F. DECEMBERS WITH MEANS 32.0 OR LOWER (listed by 30-year intervals slightly modified, 1869-1900 (8), 1901-30 (7), 1931-60 (6), 1961-90 (4), 1991-2024 (1). 1871 (29.2), 1872 (28.3), 1876 (24.9), 1880 (26.5), 1882 (30.6), 1883 (32.0), 1886 (29.6), 1890 (29.9) 1903 (31.5), 1904 (30.3), 1910 (30.0), 1914 (31.6), 1917 (25.0), 1919 (30.2), 1926 (28.9) 1935 (30.0), 1942 (31.1), 1945 (31.0), 1955 (29.7), 1958 (29.4), 1960 (30.9) 1962 (31.5), 1963 (31.2), 1976 (29.9), 1989 (25.9) 2000 (31.1)

ORD anomaly for 1st to 15th is -11.3 F.

Looks like Friday's frontal passage (timed for around 0900h EST) could lead to a few hail or snow showers with rapidly falling temperatures? It would be around 45F before the front goes through and low to mid 30s by afternoon in W-NW winds gusting to 35 or 40 mph. Lots of ups and downs in temperature trends now to end of the month, it looks likely to average near normal so the current large negative anomaly would be essentially cut in half (balanced by a zero anomaly for half a month). But it looks very cold near the end of the current GFS run by NYE-NYD.

(cross-posted from general Dec thread) ... to give an idea of climate extremes at this point, current temps in lower MI are 5-10 F so this is a very chilly air mass coming in behind the snow ... I imagine the urban heat island will prevent the 1874 records from being surpassed but 24/12 would not surprise me as temp Sunday afternoon low Monday. It may still be warmer at 0100h Sunday to bump up that day's max, then Monday could see later warm advection spoiling another very low max. But these low max values probably indicate the coldest it has been in the daytime hours. As you'll know, 1917 wasn't done by any means with this cold and snowy outbreak, all-time records fell 29th to 31st and into early Jan 1918 too. The same can be said for 1933. And 1874 was followed by possibly the harshest winter of all, lots of record cold in Feb-Mar 1875. Lowest maxima for Sunday and Monday for NYC DEC 14 _ 21 (1902), 22 (1888), 23 (2010), 24 (2005), 26 (1903,1904), 27 (1898), 28 (1933) DEC 15 _ 20 (1874,1914), 22 (1917), 25 (1871), 26 (1903), 27 (1919, 1962, 2010), 28 (1904, 1905, 1916, 2017) Lowest minima for Monday DEC 15 ___ 8 (1874), 9 (1883), 10 (1914, 1917), 13 (1900, 1902), 14 (1910, 1943, 1962), 15 (1904, 1921) __ 18 (1980, 2005) coldest recent years Heaviest snowfalls 13-14 (2d totals include all > 1.0") (daily records 8.0" 13th 1917 and 5.8" 14th 2003) 1917 _9.5" (8.0+1.5) _2d record for Dec 13-14 1902 _6.1" (6.0" 13th, 0.1" 14th) 1915 _6.0" (5.0+1.0) 2003 _5.8" (all on 14th) 1889 _5.5" (all on 14th) 2013 _5.0" (all on 14th) 1942 _4.1" (all on 13th) 1922, 1945 _3.2" (all on 14th) 1904 _2.8" (on 13th, followed 4.2" on 12th for 7.0" total) 1951 _2.5" (all on 14th) +0.8" 15th = 3.3" total 1933 _2.2" (2.0+0.2) 1995 _1.7" (all on 14th) 1892 _1.5" (all on 13th), 1893 and 1907 _1.5" (all on 14th) 1981 _1.4" (all on 14th) 1923, 2017 _1.2" (all on 14th) _ 2017 added 1.2" 15th for 2.4" total. 1909 _1.0" (all on 13th)

Temps in mid 20s by morning, could be very icy on untreated roads. Could fall as low as 0-5 F in rural areas by midnight Sunday, temp now in parts of lower MI despite daytime heating and lakes being 45 F. I see 498 dm thickness indicated at present there, modifies only slightly heading to coast.

Lowest maxima for Sunday and Monday for NYC DEC 14 _ 21 (1902), 22 (1888), 23 (2010), 24 (2005), 26 (1903,1904), 27 (1898), 28 (1933) DEC 15 _ 20 (1874,1914), 22 (1917), 25 (1871), 26 (1903), 27 (1919, 1962, 2010), 28 (1904, 1905, 1916, 2017) Lowest minima for Monday DEC 15 ___ 8 (1874), 9 (1883), 10 (1914, 1917), 13 (1900, 1902), 14 (1910, 1943, 1962), 15 (1904, 1921) __ 18 (1980, 2005) coldest recent years Heaviest snowfalls 13-14 (2d totals include all > 1.0") 1917 _9.5" (8.0+1.5) 1902 _6.1" (6.0" 13th, 0.1" 14th) 1915 _6.0" (5.0+1.0) 2003 _5.8" (all on 14th) 1889 _5.5" (all on 14th) 2013 _5.0" (all on 14th) 1942 _4.1" (all on 13th) 1922, 1945 _3.2" (all on 14th) 1904 _2.8" (on 13th, followed 4.2" on 12th for 7.0" total) 1951 _2.5" (all on 14th) +0.8" 15th = 3.3" total 1933 _2.2" (2.0+0.2) 1995 _1.7" (all on 14th) 1892 _1.5" (all on 13th), 1893 and 1907 _1.5" (all on 14th) 1981 _1.4" (all on 14th) 1923, 2017 _1.2" (all on 14th) _ 2017 added 1.2" 15th for 2.4" total. 1909 _1.0" (all on 13th)

<<< LOWEST DECEMBER MAXIMUM TEMPERATURES >>> Rank __ Year __ Temp _ 01 ____ 1917 __ 47 (1st) _t02 ____ 1872 __ 49 (15th), 1876 _ 49 (13th), 1880 _ 49 (5th), 1890 _ 49 (3rd), 1926 _ 49 (14th) _t07 ____ 1874 __ 51 (3rd), 1882 _ 51 (6th), 1904 _ 51 (28th) _t10 ____ 1909 __ 53 (6,13,14), 1944 _ 53 (8th), 1955 _ 53 (3rd), 1989 _ 53 (31st) (was 2nd lowest 48 before that) _t14 ____ 1903 __ 54 (13th), 1910 _ 54 (30th), 1945 _ 54 (8th), 1997 _ 54 (16th) _t18 ____ 1871 __ 55 (23rd), 1883 _ 55 (8th), 1886 _ 55 (24th), 1888 _ 55 (17th), 1902 _ 55 (22nd) ___ ___ t18 __ 1933 _ 55 (25th), 1958 _ 55 (5th), 1963 _ 55 (8th), 1976 _ 55 (7th), 1985 _ 55 (2nd, 24th), ___ ___ t18 __ 1995 _ 55 (3rd), 2005 _ 55 (24th) _t30 ____ 1907 __ 56 (10th), 1929 _ 56 (14,15,19), 1935 _ 56 (9th), 1974 _ 56 (8th), 1977 _ 56 (14th) _t35 ____ 1870 __ 57 (4th), 1894 _ 55 (12th), 1896 _ 57 (13th), 1898 _ 57 (30th), 1907 _ 57 (23rd), ___ ___ t35 _ 1915 _ 57 (18th), 1922 _ 57 (1st), 1943 _ 57 (9th), 1959 _ 57 (13th) _t44 ____ 1887 __ 58 (11th), 1892 _ 58 (8th), 1913 _ 58 (3rd), 1920 _ 58 (14th) ___ ___ _t44 _ 1925 _ 58 (5th, 6th), 1930 _ 58 (1st), 1942 _ 58 (2nd), 1947 _ 58 (3rd), 1948 _ 58 (13th), ___ ___ _t44 _ 1961 _ 58 (5th), 1981 _ 58 (2nd), 2003 _ 58 (13th), 2019 _ 58 (10th) _t57 ____ 1877 __ 59 (20th), 1884 __ 59 (31st), 1893 __ 59 (16th), 1899 _ 59 (11th,12th), 1900 _ 59 (24th), ___ ___ t57 _ 1905 _ 59 (3rd), 1906 _ 59 (31st), 1921 _ 59 (1st)1952 _ 59 (11th), 1957 _ 59 (20th), ___ ___ t57 _ 1972 _ 59 (31st), 1983 _ 59 (12th, 13th), 1986 _ 59 (3rd), 2004 _ 59 (8th, 23rd) ================================================ Up to 1910, it was normal for December to fail to break 59 F, it happened in 30 of 42 years (71%). From 1911 to 1960 it happened 23 more times (46%). From 1961 to 2000 it happened 13 more times (33%). From 2001 to 2024 it happened 4 more times (17%). (2003,04,05,19) Overall it has happened 70 times (45%). The interval 2006 to 2018 (13 Decembers) is the longest interval without a sub-60 maximum value. Before that, the longest such interval was ten years (1964 to 1973) and before that six years (1936 to 1941). The average value for all years is 60.3 F. Since 1961 the average is 62.2 F. Since 1990 it is 62.9 F.

<<< HALL OF SHAME DECEMBER SNOWFALLS >>> (with rest of seasons) Winter ____ OCT _NOV _DEC _JAN _FEB _MAR _APR ___ TOTAL 1877-78 ___ 0.0 __ Tr ___ 0.0 __ 6.1 __ 2.0 __ 0.0 __ 0.0 __ _ 8.1 _ 1882-83 ___ 0.0 _14.0 ___ 0.0 __ 9.4 __10.2 _ 10.0 __0.5 _ _ 44.1 _ 1891-92 ___ 0.0 __ Tr ___ 0.0 __12.2 __ 0.1 __12.0 __ 1.0 _ _ 25.3 _ 2006-07 ___ 0.0 __ 0.0 __ 0.0 __ 2.6 __ 3.8 __ 6.0 __ Tr _ _12.4 _ 2011-12 ___ 2.9 __ 0.0 __ 0.0 __ 4.3 __ 0.2 __ 0.0 __ 0.0 _ __ 7.4 _ 1885-86 ___ 0.0 __ Tr ___ Tr ___13.5 __ 5.3 __ 1,.0 __ 1.0 _ _ 20.8 _ 1888-89 ___ 0.0 __ 1.5 __ Tr ___ 4.0 __ 7.0 __ 4.0 __ 0.0 _ _ 16.5 _ 1895-96 ___ 0.0 __ Tr ___ Tr ___ 3.0 __ 9.5 __30.5 __3.0 _ _ 46.0 _ 1936-37 ___ Tr ___ 3.2 ___Tr ___ 6.5 __ 3.4 __ 2.5 __ Tr __ _ 15.6 _ 1943-44 ___ 0.0 __ Tr ___ Tr ___ 4.8 __ 7.7 __ 4.8 __ 6.5 _ _ 23.8 _ 1953-54 ___ 0.0 __ 2.2 __ Tr ___12.7 __ 0.5 __ 0.1 __ 0.3 __ _ 15.8 _ 1965-66 ___ Tr ___ 0.0 __ Tr __ 11.6 __ 9.8 __ Tr ___ 0.0 _ _ 21.4 _ 1971-72 ___ 0.0 ___ Tr ___ Tr ___2.8 _ 17.8 __ 2.3 __ Tr __ _ 22.9 _ 1972-73 ___ Tr ___ Tr ___ Tr ____ 1.8 __ 0.8 __ 0.2 __ Tr __ __2.8 _ 1994-95 ___ 0.0 __ Tr ___ Tr ___ 0.2 __11.6 __ Tr __ Tr ___ _ 11.8 _ 1996-97 ___ 0.0 __ 0.1 __ Tr ___ 4.4 __ 3.8 __ 1.7 __ Tr __ _ 10.0 _ 1997-98 ___ 0.0 __ Tr ___ Tr ___ 0.5 __ 0.0 __ 5.0 __ 0.0 _ __ 5.5 _ 1999-2000_ 0.0 __ 0.0 __ Tr ___ 9.5 __ 5.2 __ 0.4 __ 1.2 _ _ 16.3 _ 2001-02 ___ 0.0 __ 0.0 __ Tr ___ 3.5 ___Tr ___ Tr ___ Tr __ __ 3.5 _ 2015-16 ___ 0.0 __ 0.0 __ Tr ___27.9 __ 4.0 __0.9 __ Tr __ _ 32.8 _ 2018-19 ___ 0.0 __ 6.4 __ Tr ___ 1.1 ___ 2.6 _ 10.4 __ 0.0 _ _ 20.5 _ 2022-23 ___ 0.0 __ 0.0 __ Tr ___ Tr ___ 2.2 ___0.1 __ 0.0 _ _ 2.3 _ 2023-24 ___ 0.0 __ Tr ___ Tr ___ 2.3 __ 5.2 ___ Tr __ 0.0 _ _ 7.5 _ 1899-1900_ 0.0 __ Tr ___ 0.1 ___ 1.0 __ 6.6 __ 5.9 __ Tr __ _ 13.6 _ 1900-01 ___ 0.0 __ 0.0 __ 0.1 __ 2.0 __ 7.0 __ Tr ___ 0.0 _ __ 9.1 _ 1931-32 ___ 0.0 ___2.0 ___0.1 ___0.8 __ 1.8 __ 0.6 __ Tr _ __ 5.3 _ 1954-55 ___ 0.0 __ Tr ___ 0.1 ___ 2.6 __ 5.2 __ 3.6 _ 0.0 __ _11.5 _ 1974-75 ___ 0.0 __ 0.1 __ 0.1 __ 2.0 __10.6 __ 0.3 __ Tr ___ _ 13.1 _ 2021-22 ___ 0.0 __ 0.0 __0.2 __15.3 __ 2.0 __ 0.4 __ 0.0 _ _ 17.9 _ 1906-07 ___ 0.0 __ 1.0 __ 0.3 __11.0 _ 21.8 __13.3 __ 5.8 _ _ 53.2 _ 1913-14 ____0.0 __ Tr ___ 0.3 __ 1.3 __17.4 __21.5 __ Tr __ _ 40.5 _ 1918-19 ____0.0 __ 0.0 __ 0.3 __ 0.3 __ 0.5 __ 2.7 __ Tr __ __3.8 _ 1941-42 ___ 0.0 __ 0.0 __ 0.3 __ 6.4 __ 1.9 __ 0.5 __ 2.2 _ _ 11.3 _ 1988-89 ___ 0.0 __ 0.0 __ 0.3 __ 5.0 __ 0.3 __ 2.5 __0.0 _ __ 8.1 _ 1977-78 ___ 0.0 __ 0.2 __ 0.4__20.3 _23.0 __6.8 __ Tr __ _ 50.7 _ 1992-93 ___ 0.0 __ 0.0 __ 0.4 __ 1.5 _ 10.7 _11.9 __ 0.0 _ _ 24.5 _ 2012-13 ___ 0.0 __ 4.7 __ 0.4 __ 1.5 __12.2 __ 7.3 __ 0.0 _ _ 26.1 _ 1978-79 ___ 0.0 __ 2.2 __ 0.5 __ 6.6 _20.1 __ Tr ___ Tr ___ _ 29.4 _ 1986-87 ___ 0.0 __ Tr ___ 0.6 __13.6 __ 7.0 __ 1.9 __ 0.0 _ _ 23.1 _ 1937-38 ___ Tr ___ 0.8 __ 0.7 __ 6.5 __ Tr ___ 0.7 __ 6.4 __ _15.1 _ 1991-92 ___ 0.0 __ Tr ___ 0.7 __ 1.5 ___ 1.0 __ 9.4 __ Tr __ _ 12.6 _ 1956-57 ___ 0.0 __ Tr ___ 0.9 __ 8.9 __ 7.0 __ 2.6 __ 2.5 _ _ 21.9 _ 1985-86 ___ 0.0 __ Tr ___ 0.9 __ 2.2 __ 9.9 __ Tr ___ Tr __ _ 13.0 _ 1875-76 ___ 0.0 __ 0.0 __ 1.0 __ 1.5 __ 12.5 __ 3.8 __ 0.0 _ _ 18.8 _ 1905-06 ___ 0.0 __ 0.0 __ 1.0 __ 1.5 __ 6.0 __ 11.5 __ Tr _ _ 20.0 _ 1934-35 ___ Tr ___ Tr ____1.0 __23.6 __ 7.2 __ 2.0 __ Tr _ _ 33.8 _ 2014-15 ___ 0.0 __ 0.2 __ 1.0 __16.9 _ 13.6 _18.6 __ 0.0 _ _ 50.3 _ 1881-82 ___ 0.0 __ Tr ___ 1.3 __ 17.5 __ 9.3 __ 2.8 __ 0.5 _ _ 31.4 _ 1946-47 ___ 0.0 __ 0.0 ___1.3 __ 5.5 __ 17.7 __ 6.1 __ Tr __ _ 30.6 _ 1949-50 ___ 0.0 __ 0.5 __ 1.3 ___ 0.4 __ 8.5 __ 1.4 __ 1.9 __ _14.0 _ 1989-90 ___ 0.0 __ 4.7 __ 1.4 __ 1.8 __ 1.8 ___ 3.1 __ 0.6 _ _ 13.4 _ 1898-99 ___ 0.0 __19.0 __ 1.5 __ 5.3 __25.3 __4.8 __ 0.0 _ _ 55.9 _ __________________________ From this arbitrary cutoff at 1.5" for Dec snow, there are 52 (of 156) winter seasons where Dec snow is less than 1.5" and of those, 23 had no snow or a trace amount and five more just 0.1". A few of those cases had significant snow before December, notably 1882-83 and 1898-99. So there may have been snow on the ground for the first portion of some of these futile Decembers. A few were quite cold or even very cold (1989), so that small amounts of snow would have persisted longer. The interesting thing here is the frequency of nearly snow-free Decembers (0.2" or less, about one in five) and low-snowfall cases (0.3" to 1.5") expanding that to one in three, so it is almost a normal feature of the climate. the Dec average snowfall is clearly influenced by a few heavy falls such as 1947, and the median is probably lower than the mean. Also interesting is a significant number of very good snowfall winters following on, such as 1898-1899, 2014-2015, 1977-1978, and 1913-14. The median seasonal snowfall after a hall of shame December is 16.0" which shows that a poor December is often an indicator of a poor winter, but there are plenty of exceptions to inspire some optimism. The number of exceptions increases towards the cutoff point, it seems that 1.0" or more snowfall is not a contra-indication for the chances of an average season eventually.

WHAT? __ trace of snow WHERE? __ on ground WHEN? __ later IMPACTS __ none, dog may sniff at it FUTURE __ bleak in Texas, get out while you still can

It was also quite mild up north here, near 50 F in the Columbia valley (Trail BC) where there is no snow at all, and 45F at my elevation where we still have a bit of snow cover, mostly frozen slush at this point. Driving down the hill into Trail it was evident that the snow line was just below 3,000' asl here. (at the border the valley is down around 1500' asl). It was almost jacket-free mild in the valley and you do see the odd person wearing shorts even in this ski resort area (making a statement of some kind, no doubt). A minor renewal of the major 2021 Fraser valley flood disaster is underway. The Nooksack River which drains the Mount Baker region into Puget Sound had a natural outflow channel before modern times through a flat area near Abbotsford BC known as the Sumas Prairie. There was a natural lake that was drained for intensive agriculture, and of course in very wet seasons that lake tries to fill up, and largely succeeded in Nov 2021. At this point, some water 2 or 3 feet deep has crossed the border, mostly overflow from the Nooksack although there are some tributaries of the Fraser that flood also. There is some infrastructure to channel these overflows into drainage canals that are then pumped over a low divide into the Fraser. In Nov 2021 the Fraser was also flooding so this failed leading to a very rapid inundation to a level of 10-15 feet in some areas. This potential has been known for decades and you would think massive infrastructure would have been built to deal with it, but for whatever reason we are stuck with the rather ineffective smaller scale plans that only work in moderately wet weather conditions. This is because our BC provincial politics seem to be based on a combination of salmon worship and endless talk about possible plans but not starting any of them for fear of offending the spirit of the wild bear. At least that's how it was explained to me at the Indoctrination Center.

Two Decembers that flipped very greatly from cold first half (+2-4 days) to mild second half would be 1875 and 1895. The means changed as follows: 1895 ___ mean 1-17 30.7 ___ mean 18-31 47.7 ___ overall 38.4 1875 ___ mean 1-20 29.1 ___ mean 19-31 41.3 ___ overall 33.4 The largest upward shifts in recent Decembers are 2003 ___ mean 1-21 34.5 ___ mean 22-31 44.2 ___ overall 37.6 2005 ___ mean 1-22 32.0 ___ mean 23-31 43.2 ___ overall 35.3 The most prolific change was in Dec 1895 and most of the rest of the winter (Jan-Mar 1896) turned quite cold again. Winter 1875-76 remained mild well into Feb 1876, March was cold.

If history repeats, with the 1946 record highs for today, it is just one year and sixteen days to the monumental blizzard of 2026.

Least favorite type of weather here, cold rain falling on snow and slowly turning it to slush. About 5" of snow on ground yesterday is now basically 3" of gloop. Not so bad above 4,000' so far, ski resort slopes are mostly up higher than that. Around 37 F at my elevation, mid-40s and mostly bare ground lower down in Columbia valley.

Presumably the tracked component began on Oct 27 and its motion is prograde at low latitudes so the closer it gets to the center of the circle, the closer to the equator it has tracked. The current location is where the red portion of the track begins (on Dec 5 as posted). The labels around the outside of the graph show that the frame of reference is as follows ... left is around 60 deg W longitude (tropical N Atlantic near Trinidad), bottom is around 30 deg east (east Africa), right is 120 deg E (w Indonesia) and the top of the square is 150 W (south of Hawaii). The component being tracked (almost always a generally prograde motion from west to east, you can see one brief retrograde period labelled early Nov) is anomalous tropical convection. The MJO assumption is that this will anchor the dynamics of the higher latitude ridge-trough pattern that drives the jet stream in the mid-latitudes. So to sum up, the diagram tracks the motion of this forcing over about two months with 45 past days and 15 future days projected. In this case the feature has crossed the equatorial Pacific and moved across at least part of central America where it has begun to drift closer to the equator. It is progged to continue that motion for 2-3 days and then slowly reverse back towards the subtropics. There is no longer-range projection shown but one could assume the later December into January track would take it across Africa into the Indian Ocean. But I don't follow it myself, just aware of what others think it may mean to long-range prospects. Because it's not my main focus I may have some of these details wrong, so perhaps somebody more familiar with the diagram can set us straight. I think the phrase Maritime Continent is a reference to the many islands of Indonesia and the Philippines as well as Australia and New Zealand in general terms. What I would not swear to is that the diagram is meant to convey equal differentials of longitude, it may be somewhat schematic on that, and the scale of the latitude range is not really clear but I assume the circle is the tropic of Cancer and the center of the diagram is the equator. It would probably be rare for the tracked component to get to any latitude much greater than 25 N.

Friday's daytime max of 30F at NYC would have been the sixth lowest maximum for the date. The record low max was 22F in 1886. Also colder were 24F in 1926, 27F in 1901, 28F in 1893, and 29F in 1871. The 30F was set to replace 31F (2002) for lowest of the past 99 years, but the daily max then crept up to 32F before midnight, so all of the above was amended as a few more days crept into the mix at 31 or 32 F. The minimum of 20F (despite the much greater urban heat island now present) was lower than all but six years, most of them well back in the records. The lowest reading was 11F in 1926, followed by 13F in 1886, 14F in 1871, and 15F in 1935. Also colder were 19F lows in 1901 and 1911 (and 2025 also tied 20F 1893). Friday was (until the slight evening rise) slightly colder than the same date in 1989. A benchmark cold day early in December in relatively recent times would be Dec 3, 1976 (max 23, min 9 both records) followed by Dec 3, 1966 (max 25, min 15 with 14 the following morning before a massive warming trend culminating with a record high 66F on the 9th). I remember reading my own backyard thermometer (30w Toronto) in that 1966 period when I was a high school senior, at my home weather station we went from a low of -2 F to a midnight high of 60 F over those same days, and there was a very high barometric pressure with the cold spell. There was no snow on the ground either except for traces from a light fall before the cold snap, the November had been very wet and mild.

White rain gradually turned to powdery snow at 1.5" hour rates, ski resort locally is opening this weekend and saying wow, glad we didn't invest in snowmakers after all. ... 32 F, hills are nearly impassable locally.

Enjoyed reading all that in part because it tends to reinforce what I was thinking about this coming winter, lots of cold air masses with extreme cold potential at times especially in the Midwest U.S. ... the storm on Tuesday looks like it wants to explode off Cape Cod and will be a formidable storm for Nova Scotia, perhaps this cycle will move up in time slightly and eastern New England will be seeing a major event but at the moment it looks to be more like a moderate one except perhaps on the cape. The 18z GFS is just one arctic high after another for central regions, could be running some -5 to -10 anomalies this month. And I believe there is a very good correlation of Dec to Jan temp anomalies, 1989-1990 being a significant exception.

Will be interesting to see if this system can get enough organization to surpass 1-2 inches anywhere, at least it doesn't have much danger of WAA becoming a problem, the air mass is brutally cold as far south as n AR and n MS at present, but clearly the missing ingredient is energy, worst case scenario is just 6-12 hours of light barely accum snow with 0.5"type totals, but with the relatively warm water in Chesapeake Bay interacting with the weak easterly flow it could deliver 1.5 to 3.0 inches in a few spots, I hope. By the way, the latest GFS run looks like the coldest Dec since 2014 or even 1989 in some parts of the country, just one arctic high after another. I think you're in for three or four at least minor snowfalls and few days very much above 40 F.

A workaround for calculating means with traces is to find the sum, and divide it by the number of years. (not =AVERAGE(A1:A30) but =SUM(A1:A30)/30 (for 30 years). Easy peasy. Disclaimer, my excel program is 2007 vintage, and they may have "improved" that procedure out of existence. But I can add columns where I cannot average them. Also if you wanted to know how many traces there were in 156 years or however many, the procedure there is =COUNTIF(A1:A156,"T") (just saying A because I am Canadian, your data may be in column USA). Free laffs with this stats lesson. I used "T" in my example and not "Tr" or "trace" but use whatever form your traces actually show up, I have NYC data with T and Toronto data with Tr ... and I found that on average about 20 to 25 per cent of days have a trace report.

Both me and Jebman are within shouting distance of the middle of the table. Whodathunkit?

Please note, all other scoring is located back before December forecasts started to appear, so scroll back past the first of those (from Scotty) and past the intro post for December (which I never did edit into scoring) and all the scoring will be found in one combined November scoring table and annual update. Tom continues to lead the contest and it looks like a very interesting scenario for the contest with severe cold on some guidance and in some forecasts (but not all). Meanwhile, the four seasons contest is now final and here are the results of that ... Four Seasons 2024-2025 Final Report after Autumn 2025 scoring 12 points to each seasonal winner, 10 points down to 1 point for rest of field, and 1 point for all entrants with at least 2 of 3 contests entered. (2025 annual leader to end of November, Tom, had a low score in Dec 2024 which explains how this is closer than the points contest for annual 2025) ___________________________ winter _______ spring ______ summer_______ autumn ________________ Contest year FORECASTER ____________TOTAL_pts___TOTAL_pts __TOTAL_pts ___Sep Oct Nov_ TOTAL _pts __TOTAL Points ___ Consensus __________ 1771 _ 9.7 __ 1767 __7.4 __ 2088_ 10 ___ 676_688_595 _ 1959 _ 10 ___ 37.1 so_whats_happening _____1662 __ 8 ___ 1805 __ 8 ___ 2038 __ 8 ____670_676_569 _ 1915 _ 7t ____ 31 RJay _____________________ 1703 __ 9 ___ 1689 __ 5 ___ 1972 __ 5 ____674_612_701 _ 1987 _ 12 ____ 31 Don Sutherland1 _________ 1587 __ 5 ____1733 __ 6 ___ 2088 _ 10____654_634_633 _ 1920 _ 8 ____ 29 Tom ______________________1417 __ 1 ____ 2053 _ 12 ___ 2154 __12 ___590_700_583 _ 1873 _ 3 ____ 28 Scotty Lightning _________ 1542 __ 4 ____1741 __ 7 ___ 2052 __ 9 ____738_650_507 _ 1895 _ 4 ____ 24 wxallannj _________________1800 _ 10 ___ 1561 __ 3 ___ 1906 __ 2 ____662_650_635 _ 1947 _ 9 ____ 24 hudsonvalley21 __________ 1532 __ 3 ___ 1933 __ 9 ___ 1950 __ 4 ____690_700_509 _1899 _ 5 ____ 21 StormchaserChuck ______ 1328 __ 1 ____1953 __10 ___ 2010 __ 7 ____490_570_ ---_ 1060 _ 1 _____ 19 BKViking _________________1805 _ 12 ___ 1621 ___ 4 ___ 692 __ 0 ____490_666_571 _ 1727 _ 1 _____ 17 wxdude64 _______________ 1653 __ 7 ___ 1436 __ 1 ___ 1980 __ 6 ____550_578_310 _ 1438 _ 1 ____ 15 RodneyS ________________ 1488 __ 2 ____ 1474 __ 2 ___ 1938 __ 3 ___ 552_772_591 _ 1915 _ 7t ____14 Roger Smith _____________ 1617 __ 6 ____ 1368 __ 1 ___ 1880 __ 1 ____738_554_469 _ 1761 _ 2 ____ 10 Yoda ____________________ -- -- __ 0 ____ -- -- ___ 0 ___ 542 ___0 ___ 678_686_595 _ 1959 _10 ____10 ___ Normal _____________ 1387 __ 1 ___ 1440 ____1 ____ 1778 __ 1 ___ 664_578_454 _1696 _ 1 ____ 4 Ephesians2 _____________ -- -- __ 0 ____ -- -- ___ 0 ____ --- ___0 ___ ---_ 574_ 531 _ 1105 _ 1 _____ 1 ___________________________ So we have a tie in points at the top (although Consensus is the contest winner too) ... I will declare it a tied win for RJay and so_whats_happening, meanwhile DonSutherland1 also had a strong finish into third place and contest leader Tom was just a bit off his previous pace to end up in fourth, but with so many totals just a few points ahead of Tom he was only able to advance slightly this past season -- the points differential is not making much impact on his overall contest lead, as you can see there has not been a large spread in the autumn points for most of the forecasters. Yoda had a very good first season after joining in August, finishing second in points for autumn. I don't score Persistence in the four seasons contest but probably Persistence would have been lucky to add any points to Normal's basic total.

Table of forecasts for December 2025 FORECASTER __________________ DCA _NYC _BOS __ORD _ATL _IAH ___ DEN _PHX _SEA Mercurial ______________________ +4.0 _+2.0 _+1.0 __-0.5 _+0.5 _+2.0___ -1.0 _ -3.0 _ -1.5 hudsonvalley21 ________________ +1.3 _+1.4 _+1.0 __ -1.6 _+1.7 _ +1.5 ___ +0.4 _+1.8 _-0.3 Scotty Lightning _______________ +1.0 _+1.0 _+0.5 __ -1.0 _+0.5 _+1.0 ___+1.0 _+1.0 _+0.5 ____ Normal ____________________ 0.0 __0.0 __0.0 ____ 0.0 __0.0 __0.0 ____ 0.0 __0.0 __0.0 wxallannj ______________________ -1.0 _ -1.1 __-1.3 ___ -0.7 _+0.8 _+1.7 ___+2.0 _+2.2 _+2.5 DonSutherland1 ________________-1.0 _ -2.0 _-2.0 ___ -3.3 _+2.5 _+1.6 ___+1.4 _+1.1 _ +0.1 BKViking _______________________-1.2 _ -1.3 _ -1.7 ___ -1.7 _+0.9 _+1.2 ___ +1.3 _+2.2 _+1.5 ___ Consensus ________________ -1.3 _ -1.7 _-1.8 ___ -2.8 _+0.7 _ +1.1 ___ +1.0 _+1.5 _+0.5 so_whats_happening __________ -1.4 _ -1.3 _ -1.6 ___ -2.6 _+0.8 _+1.2 ___+1.1 _ +2.1 _ +0.6 Tom ____________________________-1.9 _ -2.7 _-2.8 ___ -3.9 _-0.9 _+0.5 ___+0.6 _+1.5 _+1.1 RJay ___________________________ -2.0 _-2.0 _-2.0 ___ -3.0 _+1.2 _+0.5 ___+1.0 _+1.5 _+0.5 RodneyS _______________________ -3.6 _-3.0 _-2.3 ___ -4.7 _-2.5 _+0.9 ___+1.3 _+0.5 _+0.5 Roger Smith ____________________-4.0 _-3.8 _-4.5 __ -5.9 _ -3.3 _ -1.5 ___-3.6 _ -2.9 _ -2.4 wxdude64 ______________________-4.4 _-3.1 _-3.3 __ -4.7 _ -2.5 _ -0.7 ___-0.9 _+0.8 _+2.3 ----------------- (highest and lowest forecasts above are color coded; all forecasts are below normal for ORD) __ Persistence ___(Nov 2025)___ +0.4 _-0.8 _-0.5 __+1.1 _+3.5 _+5.4 ___+5.7 _+3.9 _+2.1 ===================== ____ Table of Snowfall forecasts for winter 2025-26 ____ FORECASTER __________________ DCA _NYC _BOS __ORD _DTW _BUF ___ DEN _SEA _BTV wxallannj _______________________23.0 _28.0 _ 28.0 __45.0 _44.0 _89.0 ___44.0 _18.0 _ 99.0 Tom ____________________________ 19.5 _ 31.1 _ 44.5 __ 40.1 _42.4 _102.4 __ 54.8 _ 6.1 _ 81.4 hudsonvalley21 ________________ 18.0 _ 22.0 _ 31.0 __ 32.0 _42.0 _93.0 ___52.0 _ 4.0 _ 88.0 wxdude64 _____________________ 15.6 _ 28.6 _ 41.1 ___30.3 _45.5_ 101.5 ___ 66.2 _ 4.7 _ 93.3 BKViking _______________________ 15.0 _ 32.0 _ 41.0 __40.0 _22.0_ 96.0 ___ 58.0 _13.0 _ 80.0 Rjay ____________________________ 15.0 _ 21.0 _ 44.0 __50.0 _33.0_ 100.0 ___65.0 _ 6.0 _ 90.0 ___ Consensus _________________ 15.0 _ 22.5 _ 39.5 __40.1 _42.2 _ 94.5 ___ 55.2 _ 6.1 _ 87.5 Scotty Lightning _______________ 15.0 _ 20.0 _ 25.0 __ 30.0 _45.0 _85.0 ___ 50.0 _ 5.0 _ 95.0 so_whats_happening __________ 14.0 _ 23.0 _ 39.0 __ 42.0 _40.0 _91.0 ___ 38.0 _ 4.0 _ 87.0 Roger Smith ____________________12.8 _ 25.6 _ 50.7 __ 57.3 _ 61.5 _115.7 ___ 70.0 _12.5 _ 88.8 DonSutherland1 ________________10.0 _ 20.0 _ 40.0 __ 37.5 _45.0 _ 92.0 ___ 40.0 _ 6.5 _ 80.0 RodneyS ________________________ 6.7 _ 18.9 _ 35.7 __ 44.4 _49.1 _ 99.9 ___ 55.6 _ 9.1 _ 70.4 Mercurial ________________________1.0 _ 10.0 _ 20.0 __ 30.0 _ 30.0 _70.0 ___ 65.0 _ 6.0 _ 60.0 ___ snowfall to date (Dec 15) ____1.5 __2.9 __ 1.3 ___ 17.3 __ 12.6 _ 24.6 ___ 4.5 _ 0.0 _ 20.0 ===================== Consensus for snowfall is the median of 12 forecasts

TEMP _________DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA -4.0 -3.8 -4.5 -5.9 -3.3 -1.5 -3.6 -2.9 -2.4 SNOW _______ DCA _ NYC _ BOS ___ ORD ____DTW ___ BUF __ DEN _ SEA _ BTV 12.8" 25.6" 50.7" 57.3" 61.5" 115.7" 70.0" 12.5" 88.8"