Second Half of Winter ~ Same as the First?

The actual temperature trend of the winter has unfolded as suggested by preferred Winter Analogues (see table below and clips from original outlook). Basically after the warm fall  (especially November), research suggested a change in the trend would commence in December. A sharper contrast in the warm pattern was projected with a pattern change to more seasonal weather. Colder temperatures more typical for early winter were in the offing as December unfolded.

 

In my opening Winter 2024-25 Outlook headline; I questioned "Another milder winter in store, is this becoming a habit - or is it?" mainly because last winter (2023-24) was like a perpetual fall in Michigan or basically, like a "Kentuckian Winter".  In addition; many of our previous winters have been predominately mild with just a few weeks to month of real cold winter weather. Original Winter 2024-25 Outlook.

 

Best thing to do is to compare what has transpired the past few months, compare it to analogues and trends, also look at hemispheric patterns from previous similar analogue winters and patterns locally. We've got at least 3 analogues that fit the bill, but which one(s) if any, will pan out into April?

 

First, lets check the temperature/precipitation pattern for the first half of the cold season...  

Dec Temp/Pcpn: Both temperatures and precipitation showed the beginning of the winter milder and wetter with 3.27" recorded. However; colder spells came more frequently with the monthly average coming in mainly below normal until just after Christmas when a burst of warmer weather boosted the average 2.0 degrees above.

Jan Temp/Pcpn: a complete reversal in both temperature and precipitation came to fruition with both below normal. With an average temperature of 23.0, the average departure came in just shy of 3.0 degrees /-2.8/ below normal.

 

Colder snaps did indeed start in December but they were offset enough with warmer spells mainly late in the month. While November's average temperature was nearly +7.0 degrees above normal; December's dropped to just +2.0 degrees above normal with January's average falling -3.0 degrees below normal - quite a dramatic turn-around (a departure turn-around of 10 degrees). The colder trend is easily seen and verified.

 

Interestingly, this did reflect all of the analogues overall trend change from the warmer fall into the colder first part of Winter. When just looking at each individual month below or above temperatures, averages were projected to fall closer to below. The analogues strongly suggested the trend of colder weather coming in the first half of the winter starting sometime in December. Later, as the winter to spring evolved, it became more mixed again with averages actually reverted back to above normal mainly because of a few recent warmer winters.

 

Snowfall thus far this winter has been low and nearly half below the normal snowfall through the end of January.

 

 SNOWFALL (IN)                                                              
                                                              NORM      DEP
  MONTH TO DATE JAN   8.9           14.0        -5.1       
  SINCE DEC 1                 12.5           22.9      -10.4      

  SEASON                         14.3           24.8      -10.5              
 

First, lets look at the projected snow averages for the winter -which actually have averaged lighter than normal - when all (and preferred analogue winters) are  considered. By the end of January 2025 thus far, only 14.1" at DTW has fallen which is just under 10" below average by the end of January (see official stats from DTW). On average about 2 feet of snow can be expected by this time.                             

Winter 2024-25 Analogue Snowfalls
DETROIT	SEA TOT	SEASON
SEASON	44.4	1
1942-43	16.6	1
1952-53	49.2	2
1964-65	50.6	1
1966-67	35.4	2
1970-71	51.8	2
1983-84	27.6	3
1995-96	36.3	4
2005-06	37.9	5
	Ave 38.2
	Norm 45.0
	Dep - 6.8

Checking out the preferred Winter Analogues below snowfall amounts below; obviously one would ask, why is 1942-43 since we didn't have anywhere near 18.4" of snow in January? Obviously, snowstorms (when they do come) don't usually come all neatly packed in a particular month. What we are looking for here is the previous analogue trends before mid-end of the winter. Thus, that 18.4" of snow could come during the second half of the snow season (Feb-Mar) and would still suffice for a trend seen for a snowier middle to end of the season.

Basically; heaviest snowfalls in two of the analogue seasons (1942-43 and 1964-65) came middle to end of the season. In the case of the Winter of 1970-71, the seasonal snowfall was lighter than normal and was distributed throughout the season.

So according to the preferred analogues that have verified in trend; the normal to below snowfall seen in all the winters (38.2"/-6.2) still holds sway. Temperatures become more variable later winter into spring relative to normal. Some analogues remained cold while others moderate and actually warm to above normal. The over preferred analogues thus far through February /Dec-Feb/ keep temperatures ending normal to below for the winter.

A	DETROIT	T	E	M	P	S		P
N	SEASON	DEC	JAN	FEB	WNT AVE	WINTER	NAO/SC	SEASON
A	1942-43-n **	25.6	21.7	28.0	25.1	1	N/SC--	1942-43
O	1964-65-a **	30.4	25.5	26.6	27.5	1	N-/SC	1964-65
U	1970-71-n **	29.0	20.7	27.4	25.7	2	N-/SC++	1970-71
	DETROIT	S	N	O	W	F	A	L	L
W	SEASON	OCT	NOV	DEC	JAN	FEB	MAR	APR	SEA TOT
E	1942-43	T	4.4	9.2	18.4	2.7	2.9	6.8	44.4
K	1964-65	T	2.6	8.4	7.1	15.8	12.9	2.4	49.2
L	1970-71	0.0	1.7	9.8	8.7	5.9	8.7	0.6	35.4

Model Outlook into February: another moderation to warming of the stratosphere has been projected and continues with an actual split and lowering of the polar vortex(s) further south over the mid latitudes in some areas (the States and Europe). This occurs occasionally and can produce unseasonably cold, arctic/polar air to drain into the mid-latitudes - the exact areas and intensity in the surface jet stream remains questionable. Sometimes the lower atmospheric engages this delivery; sometimes not so much and models have a difficult time in forecasting this change and where.  This is what is seen thus far through the mid February time-frame. A notable drop in the NAO and AO and the stratospheric moderation or warming which at this point is forecast. This will encourage more of a stormy period and fluctuations of temperatures; so stay tuned.

 

 

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian

 

JANUARY 2025 IS PROVING TO END UP A COLDER THAN NORMAL MONTH AS NEGATIVE DEPARTURES GROW!

The switch from unseasonably warm month in November (and resulting fall) to a mixed cold and mild December to a colder than on average first half of January. The worst is yet to come as us meteorologists look at the waves of Arctic cold projected possibly into the end of the month. This jives well with the Stratospheric moderation-warming at 30-10mb mentioned here days ago.

While cold looks more & more likely with brief moderations between, no clear-cut storm system has been ginned-up by models with any certainly. More light snow is expected this weekend as temperatures moderate to the lower 30s (a veritable heat-wave) before plummeting back down into the deep bone-chilling, wind-chilling cold later in the weekend into next week! Later in the month into early February is beginning to look interesting but as for the next couple of weeks…

 

This was written Tue afternoon /14th/ by extended forecasters in Maryland and still looks good…

 

Prognostic Discussions

Valid: Jan 20 - 24, 2025 (6-10 Day Outlook)

Valid: Jan 22 - 28, 2025 (8-14 Day Outlook)

Issued: Jan 14, 2025

 

Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks

NWS Climate Prediction Center College Park, MD

300 PM EST Tue January 14 2025

 

6-10 DAY OUTLOOK FOR JAN 20 - 24 2025

A highly amplified 500-hPa height pattern is forecast across the forecast domain during the 6-10 day period, with ridging over western North America and strong troughing downstream east of the Rockies. The 0z ECENS and CMCE are quicker to lift the troughing out in the East by day-10 while the 0z GEFS maintains stronger negative height anomalies. The manual height blend indicates above-normal heights west of the Rockies and extending northward through Alaska. A +210 meter positive height anomaly center is noted just to the west of British Columbia. Below normal heights are predicted for most of the CONUS east of the Rockies, with the strongest negative anomalies (-150 meters) to the north of the Great Lakes.

 

A major Arctic air outbreak is forecast to be ongoing across the central and eastern CONUS at the start of the period. The 0z ECENS and GEFS indicate widespread daily temperature anomalies exceeding -20 deg F on days 6 and 7,corresponding with subzero temperatures across the Northern and Central Plains, Midwest, and possibly into the Interior Northeast, and minimum temperatures in the 20s deg F possibly reaching the Gulf of Mexico coast. The re-forecast and uncalibrated tools all support elevated probabilities for below-normal temperatures across nearly all of the CONUS, with the highest chances (greater than 80 percent) across the Southern Plains and much of the East. Probabilities for below-normal temperatures are reduced across the Northern Plains due to the possibility of quickly moderating temperatures as the trough lifts out, with the ECENS depicting a flip to above-normal temperatures at the end of the period.

 

Below is the CFS run (1/13/12Z) from the same period starting at Wed 1/15/25 @ 48hs. Surges of Arctic air backed by large, High Pressures /blue H's/ stacked up across the North Pole into northern Canada sliding SE from the far north

 

 

Next we'll look at which analogues actually accurately projected the first half of the winter's trend /Dec-Jan/ and what happened then - and what is more likely to occur for the winter period Feb-Mar '2025.

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian

 

 

With The First Week of a New Year Comes a Change in the Weather

The first official month of the Winter 2024-25 season brought a notable change in the prevailing unseasonably warm fall weather. For the most part; the month of December contained equal amounts of below normal temperatures and above until the end; when a quick mild spell boosted the monthly average to above normal at 33.3/+2.0. All in all; December was a fairly "snowless"  month with below average snowfall at 3.6" /normal  8.9"/ through the 31st but with above normal precipitation with 3.27". Thus far; only half our normal amount of snow has fallen this winter with 5.4" /Norm -10.8"/

The outlook for January 2025 keeps the declining temperature trend in vogue for now with a predominantly colder than normal January in store for the early - mid month period. Latest indications are a gradual stratospheric warming trend (not official SSW) far aloft over Siberia toward the North Pole will help elongate the Polar Vortex (and some of the brutal cold at the surface) and push it south (blue/purple) into the mid latitudes, including North America with some moderation. Coldest air at the surface would concentrate over the eastern two-thirds of the nation and deep into the south!

 

Projected 500 MB upper air pattern for all of January shows the elongated trough over eastern Canada into the eastern U.S.

 

With the ridging/upper high pressure building over the eastern Pacific and western U.S at times and blocking in Greenland, this will enable the delivery of Polar/Arctic air south into the U.S.

Low pressure will move along the Polar front early in the new week but at this time it appears much of the snow will stay south in the Ohio Valley. Models have had a terrible time with this system varying from a snowstorm for the southern Great Lakes to nothing, keeping it south. The dynamics and upper air pattern won't be sampled better until Friday. Any significant changes will be blogged.

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian

 

The Whitest of Christmases and Other Christmases Past and Chances for a White Christmas - 2024

Frequently during the Christmas Season, meteorologists are asked; Are we going to have white Christmas?  Generally, it is agreed among meteorologists that in order to "officially" have a white Christmas, an average of an inch of snow must cover the ground Christmas morning /7AM/, but not necessarily have to fall on Christmas. 

Mom Nature and weather models have been extremely fickle with weather day to day and week to week this holiday season. Frequently, changes in model projections and actual evolving weather many times have not coincided. Thus, the later than average White Christmas post.

At this time /Tuesday/ December 24th 2024; chances of a white Christmas across all of Southeast Lower Michigan pretty well; depends greatly where you are located. Most areas across extreme Southeast Lower Michigan (across much of Metro Detroit south to the Ohio Border) will not have a white Christmas per se' with a trace or nothing. Further west and northwest across Ann Arbor, Milford, Howell around an inch or so - therefore definitely location. Further north over Flint into the Saginaw Valley across into the Thumb Region Mainly around I-69 and north-northeast a white Christmas should hold into Christmas. Temperatures however will be close to normal with highs in the lower to mid 30s.

Christmas of 2023 was a total waste as far as white Christmas with unseasonably mild weather with temperatures in the 50s!

 

Christmas 2022; a cold blast accompanied by several inches of snow fell a few days before and on Christmas across Southeast Lower Michigan making for a white Christmas but with brutally cold wind chills well below zero.

  

On Christmas /2021/ we ended up with no white Christmas. Christmas 2020; we lucked out with generally an inch or two of snow falling over the region on Christmas Eve into Christmas morning. A nice picture-perfect light snow cover.

 

Christmas /2019/ no white Christmas was to be had - and also back in 2018; around Metro Detroit there was no white Christmas. In fact; temperatures pushed up into the 40s and 50s in the few days following Christmas. Further north from the Flint area into the Saginaw Valley and Thumb Region however; a inch or two remained on the ground for a white Christmas across that region.

Over the years, extreme Southeast Lower Michigan has averaged just under a 50 percent chance for a white Christmas.  Some years it's already on the ground, some years not, some years it melts while other years it falls on the day. However, theoretically, you could actually have nothing on the ground Christmas morning and have a snowstorm dump a foot on the region during the day and still have NO official white Christmas under the standing morning rule. It works the other way too; you could have a several inches on the ground at 7am 12/25 but warmer air and/or rain melts it away by afternoon or evening and still officially have a white Christmas.

Four years ago /2017/; an unexpected white Christmas was had in spades as low pressure system overachieved; developing robustly over the southern Great Lake/northern Ohio Valley. The system developed into a notable little snowstorm falling mainly on Christmas Eve over the southeast area as seen in this map, bringing snow for a picturesque, classic Christmas scene. The only negative - and a notable one - was the lousy driving conditions Christmas Eve into early Christmas Day but with improving conditions later for Christmas dinnertime.

For more on the system from the NWS; see here.

In 2016; even with mild weather with temperatures in the 30s; Southeast Lower Michigan was able to hold on to a white Christmas as the snow (generally 2-5") slowly melted. In fact; the day after Christmas, warm air surged into the region and pushed temperatures into mainly the 50s and took care of any remaining snow! Back in December /2015/; it was a mild and snowless Christmas with a high temperatures near 50. Of course, the year before, /2014/ contained our record breaking warm El Nino December, therefore the hopes for a white Christmas were low anyway. Back on Christmas 2014, the chances for a white Christmas were very similar to 2015 with record setting low amounts of snow for the month (in the top 5 snowless). Officially on 12/25/14 at 7am; no snow was on the ground with a trace of light rain on the date. Only a TRACE of snow had fallen up to that day in December /0.1 for the entire month/.  Most areas over the remainder of Southeast Lower Michigan had a few tenths of snow Christmas eve or Christmas but with less than the amount needed and mild temperatures rising into the upper 30s to around 40...none of the area saw a white Christmas.

More Previous Christmases back to 2004:

In 2013;  even with all the snowfall throughout last winter, officially on 12/25/13 at 7am Detroit Metro Airport had only a TRACE of snow on the ground. Most areas into the remainder of Southeast Lower Michigan had some residual snow and ice on the ground for a white Christmas. Back in 2012, enough snow did fall at Detroit Metro Arpt (an inch of fresh snow Christmas Eve) to make it an official white Christmas was on the ground as of 7AM. The necessary inch or more was also on the ground at both Flint and Saginaw. Ironically the day after Christmas, the best snowstorm of the winter season hit the region...a day late and several inches short for Christmas. A year earlier in 2011, it was a relatively mild Christmas with temperatures in the 40s and no snow on the ground; so no white Christmas. However back in 2010; residents across Southeast Lower Michigan did enjoy a white Christmas with generally 1” to 6” of snow across as temperatures hovered in the 20s. Then further back in 2009, much of the Detroit area south did not have a white Christmas but points north across Flint, Saginaw and the thumb region generally had a 1” to 3” snow cover. Back in 2008, we saw a “sloppy, melting white” Christmas. That white Christmas involved the melting of a heavy snow cover from past snows that accumulated throughout December. The best of the snowstorms came before Christmas on the 19^th (with another, lesser intense snow falling on the doorstep of Christmas, 23^rd -24^th). After, however, the heavy snow cover melted in earnest as milder air overspread the region Christmas Eve right through the 26th. Christmas of 2007, saw temperatures rise into the mid 40s to mid 50s a couple of days prior to Christmas and that, combined with light rain, pretty much took care of any hopes for a white Christmas as then, like the later Christmas of 2008, the  previous heavy snow cover melted (but this time in its entirety before Christmas). Some scattered light snow did return, skirting the landscape on Christmas Eve but most areas around Southeast Lower Michigan still only had a trace of snow for Christmas. At White Lake and Saginaw, however, the official inch of snow to make it a white Christmas was barely attained in 2007.

Going back further to the Christmas of 2006; it was also mild and therefore, there was no white Christmas. In 2005, we just barely squeaked out a white Christmas (at Detroit Metro Airport, anyway) as a mild spell moved in just before Christmas along with rain, melting the snow down from 4” to 1” by Christmas morning. Originally, there had been 8” of snow on the ground on the 15^th. The last really scenic (no slop)  with fresh white snow for Christmas occurred in 2004. A snowstorm brought heavy snow (ranging from 8”at Detroit to around 4” in Saginaw and Flint) on the 23^rd, which left the region with a nice white cover for Christmas. It was also a cold Christmas also with highs only in the teens and overnight lows below zero. 

Looking over historical weather records of Christmases past since 1900, a wide range of weather conditions were found. While most people would like to believe that Christmas in the Detroit area should be snowy-white and picturesque, more often than not, they're not. Over the past 124 (including 1900) Christmases in Detroit, 58 (or 47%) have been what would be called "white" with an inch or better of snow on the ground. Keep in mind however, these records are for Detroit; farther north in Flint, the chance of a white Christmas jumps to 56 percent, while in Saginaw and the Thumb region it rises to 61 percent. However; the past 30 year normals /1991-2020/ the shorter time-frame indicates the chance of a white Christmas at Detroit has dropped to just 35%; whereas around Flint the past 30 year norm puts it at basically a 50/50 chance (or exactly 51%). In the Saginaw region; the probability of a white Christmas has dropped to 46%.

Way back on the Christmas of 2000 was very white indeed, but as to how much of a white Christmas (snow depths) is where the confusion came in. Let me elaborate, officially at Detroit Metro Airport, just six inches of snow was recorded on the ground at 7AM Christmas Day. However, just about anywhere west/north and in the city of Detroit itself, amounts were considerably higher with generally 8 to at least 15 inches. At the National Weather Service in White Lake, 15 inches was observed on the ground Christmas 2000 morning. No additional snow fell on Christmas Day (nor was anymore really wanted with the surplus already at hand). In any event, for Detroit and surrounding communities, the six inches at Detroit Metro Airport is the official snow depth used for the area.

The snowiest Christmas (most snow falling on Christmas), occurred in 1915 when 6.4 inches fell with a snow depth of seven inches on the ground. The timing of this snowfall was impeccable for Christmas with it actually starting Christmas Eve around sunset. Then, it continued to snow through the night into Christmas day. Actually, even more than the 6.4 inches fell from the entire storm with an additional 1.6 inches falling on Christmas Eve. This gave a snowstorm total of eight inches.  A little light rain did mix with the snow during the forenoon hours of Christmas but with a high temperature of only 33, it did little to mar the "Christmas card" scene. Speaking of "Christmas card" scenes, another heavy wet snowfall blanketed the area just after the turn of the century early on Christmas in 1901. The scene is described in the historical weather books as follows:

    "Night of the 24 - 25 cloudy; moist snow continued,

     heaviest between hours of 1:30 and 4:30 am, ended

     at 6 am. amount of precipitation .62 inches. The

     street cars ran all night to keep the tracks open.

     the snow adhered to trees etc, and made a very

     beautiful scene. Depth of snow on ground at 8 am,

     5.5 inches".

 This "Norman Rockwell Christmas scene" was further enhanced by a heavy coating of frost deposited on the buildings and windows Christmas Eve due to the moisture-laden air. But just like memories of some Christmases past, this majestic Christmas scene quickly faded (melted) during the day as temperatures climbed to 41 degrees, leaving just slush , slop and water. During the Christmases of 2002 and 2003, the weather was similar to both of the white Christmases mentioned above /1901 & 1915/. Here again in 2003, snow started falling Christmas Eve and lasted into at least part of, if not all of Christmas Day. On Christmas Day 2003, snowfalls ranged from at least an inch in the far southeast corner of Lower Michigan to as much as six inches across Detroit's northern suburbs, extending northward across Flint and Saginaw. On Christmas Day of 2002, total snowfall at Detroit Metro Airport was measured at 6.4” inches for both days (Christmas Eve and Christmas) with 3.4” of it falling on Christmas Day, itself. Across all of Southeast Lower Michigan snowfalls generally ranged from four to seven inches. A picture perfect Christmas was created both years with the freshly fallen snow. Like the Christmas snowstorms of 1901 and 1915, the snow Christmas 2002 was also somewhat heavy and wet with high temperatures in the lower 30s and lows only in the mid 20s.

Probably one of the slushiest and sloppiest Christmas Days happened in 1973. What started out as a white Christmas with a heavy 7 inch snow cover, quickly melted to a meager 2” slush mess by nightfall. To add insult to injury, it rained nearly a half an inch during the day.The wettest Christmas on record occurred in 1945 when 1.16 inches of rain fell. The rain actually began Christmas Eve as a light freezing rain and continued freezing until nearly dawn on Christmas, when the temperature pushed above freezing. Until the ice melted, a few tenths of an inch of ice coated everything by Christmas dawn. Needless to say, walking and driving early the Christmas of 1945 was treacherous but Santa was in and out of town in a flash!

Without a doubt, and still in the memories of long term inhabitants of Southeast Lower Michigan, is the warmest Christmas on record, the Christmas of 1982. It was as though the whole area was shipped to Florida for the holiday! The official record high at Detroit was 64 degrees, while Flint did one degree better at 65! These readings are about normal for Tallahassee, Florida! Scenes of shirt sleeved people with shorts running or riding bikes, instead of visions of sugar plums, made the Christmas of 1982 to some Michigan Christmas traditionalist, very hard to take.  This spring-like day was complete with scattered showers and, of all things, thunderstorms! Ironically, the bitterest cold Christmas came just a year later in 1983! Maybe a payback from Mother Nature for the warm weather we were treated to, the Christmas past? The temperature plummeted Christmas eve to a record low of -9 at Detroit and was accompanied by a stiff west wind averaging 25 to 30 mph, creating life threatening wind chills at times of near 40 below zero! Santa certainly brought the North Pole with him the Christmas of 1983, when he made his rounds very early that morning. In addition to the record low Christmas eve, another record low /-10/ was established during the very early morning hours of Christmas.

These Christmases past discussed are more the extreme than the norm across extreme Southeast Lower Michigan. But they do show the variable weather that can occur at Christmas (or any other time for that matter). The "normal" (or average) highs in extreme Southeast Lower Michigan Christmas Day are in the lower 30s, while lows average in the upper teens.

And now, I'd like to wish all who read this a very Merry Christmas and/or Holiday Season and the best in 2025!  I plan on continuing my blog occasionally for the new year if the fates allow and look forward in reaching out to more people (and hear their comments and ideas) across the globe.

Making weather fun while we all learn,

Bill Deedler - SEMI_WeatherHistorian