Friday, December 22, 2023

How Often Do We See Snow on Christmas? Cold?

Maybe you remember the super warm Christmas back in 1982 when we reached 66° degrees. Perhaps you remember the following Christmas when the high temperatures was 1°. Most of remember the brutally cold period leading up to Christmas last winter (2022).

What was the Christmas weather like when you were a kid?  I created this handy chart showing the Christmas weather history for northern Ohio going back to 1940.


Monday, December 18, 2023

December 18 - Forecast Discussion - First Snow in Ages!

As of this writing (December 18 at 7am) we haven't seen shovel-able snowfall since November 28th. 

The last time this happened was...well, last year.  Here are the years where we saw less snow between Nov 28 and Dec 17. Notice how the occurrences were more sporadic before the 2000s. 

Snowfall departures across the US are also running well below normal. Interesting that portions of northern Missouri, central Kansas, North Dakota and parts of New England running well above normal.

Graphic Courtesy Ben Noll

Ohio Valley snowfall totals (as of December 15)

Friday, December 15, 2023

December 15 Forecast Update - A Look at December Thus Far

So far, December temperatures have been above normal not only across northern Ohio but across most of the US. Red colors indicate above normal temperature regions.  Check out my previous POST which goes into why the pattern has been so mild/snowless.

Snowfall thus far has also been slightly below normal for northern Ohio. Snowfall over the last 10 years through December 15. The average is around 7".  This year, snowfall has been a bit under 5".

Here is the list of the least snowy winters through the END of December.  How much snow did these winters get AFTER January 1st?  Most of these winters ended up with significant snowfall.  Only TWO ended up with below normal snowfall.  This isn't a forecast.  But it does tell us that we should never use one month (in this case December) as a predictor of the rest of the winter season.

Here's a look at the last ten Decembers going back to 2013 nationwide.  Warmer colors indicate above normal temps. Green/blue colors indicate below normal temps.  Notice how many of these years have featured more overall "warmth" than cold. The last December that featured more than 50% of the US with below normal temperatures was 2013!

Thursday, December 14, 2023

Why The Milder December? A Detailed Look Into January

Just finished a detailed video of the primary drivers of the milder December and how these drivers will influence the pattern shift into January.  Enjoy!

Monday, December 11, 2023

How Do You Define a "Harsh Winter"?


No question typifies weather subjectivity and story telling more than this one.  Ask this question and you'll get a different answer virtually every time. Here are some of responses via Twitter when I asked this question recently.  I'll analyze each one with data from Cleveland to see how often each weather occurs.  Responses are abbreviated.


1) Above average snow & below average temps

First, here is snowfall vs normal for each winter since 1960-61 using a running average.

Now winter temperatures vs average over the same time frame.  Again, we use a 10 year running average.

The only winters that fit each component (temps and snowfall) are:

1962-63, 1969-70, 1977-78, 1981-82, 1983-84, 1993-94, 1995-96, 2002-03, 2003-04, 2008-09, 2013-14 and 2014-15

2) Sustainable snow cover into April

Most Aprils rarely has sustainable snow on the ground.  Here are the total days with 1"+ snow cover for each winter since the late 1930s.  Most year its only one day. Only 6 winters had 3 or more days in April in the last 40 years.

Expanding snow cover days into March and April, we find 21 of the last 64 years with 10 days or more with snow cover between March 1 and April 15:

3) Less than 10 days without sunshine

Hard to quantify due to data limitations.

4) Extreme cold with no breaks

"Extreme cold" is arbitrary. So we'll go with total days with temperatures under 20 degrees.

5)  DJF - 45 days or more below freezing for highs AND Total snowfall 50"+

Nice graph showing the 45 days at/under freezing. Red box indicates years with total snowfall 50"+

Most recently:  2014-15, 2013-14, 2010-11, 2002-03, 2000-01, 1995-96, 1984-85, 1983-84, 1980-81

6) Below zero temps

Not many in recent years. Only 4 in 2017-18.  The two back-to-back super cold winters of 2013-14 and 2014-15 saw 23 combined.

7) Temps consistently below 32

Winters since 1969-70 where we had more than 14 straight days at/under 32 degrees. Date shows when the streak ended.

8) More than 4 weeks with more than 6" of snow on ground

Only 6 winters had more than 28 days with at least 6" snow over:
1962-63, 1976-77, 1977-78, 1978-79, 2008-09, 2009-10

9) DJF - half of days with snow cover

Most recently, these winters:

2014-15, 2013-14, 2010-11, 2009-10, 2004-05, 2002-03
1995-96, 1993-94, 1985-86, 1984-83, 1983-84, 1981-80
1980-81, 1978-79, 1977-78, 1976-77, 1967-68, 1963-67
1962-63, 1960-61

10)  Snow totals above normal

Filtering out the winters with at least 8" snow above normal we get these winters:

11)  Wind chills under -10

My nice chart I update each year denoting the total hours where we reach below zero wind chills. I noted the years in red where chills dropped under -10.  Last winter it occurred frequently around the holidays. In fact it was coldest period (using wind chill) since January 1994. Prior to last winter, the winter of 2012-22, 2018-19 and 2017-18 were the most recent winter with chills under -10.

The winter of 2008-09, 2006-07 and 2000-01 

12)  High temps under 20 degrees for 30% of the winter

Has never happened

13)  20 days with single digit temps & Frequent 10" snows

The only winters with ONE DAY 10" snowfalls are:

How about TWO DAY 10" snowfall?  That has happened 57 times.  Here are the occurrences in the last 50 winters:

How about 2 day 10" snowfalls AND 20 days with single digit temperatures in the same winter?

14)  5 snowfall events greater than 6"

Hard to believe but the most in one year (since 1960) is 6 and that happened in 2004-05.  Here is the list showing all winters with at least two.

15)  Below 10 degrees for two weeks

Since 1960, we've only had TWO WINTERS where we had more than 10 straight days with overnight lows at/under 10 degrees.  

16)  Consecutive days with at least 1" of snow cover

Last year we had only 15 days with at least an inch of snow cover. Second lowest since 1960-61. 

The top ten winters with snow cover since 1960-61:

17  Consecutive days under 40

Here is the list showing the top 15 winter and the date when the consecutive streak ended.

So you can see that everyone's definition of a harsh winter is different.  By checking history, many of these listed above don't occur as frequently as we would believe. There is definitely some availability bias here. That is we tend to create--in this case--a weather narrative using the most noticeable, seemly important information we have at our disposal. Yet in reality, that information can be incomplete. The the lack of super cold and snowy winters in recent years has seemed to artificially "enhance" our memories of what a rough winter used to be.  As is often the case, what we remember of winter weather from yesteryear gets blurred and sometimes exaggerated over time. If we experienced an historic weather events firsthand those indelible marks, can inflate--perhaps due to availability bias or recency bias (more recent events tend to be overemphasized)--what might have been a more benign event.

Either way, our feelings on winter are highly subjective and always filled with emotion unlike any other season. Let's see if winter 2023-24 conditions make these lists!

December 11 Forecast UPDATE

Some spotty light sleety snow this morning.  Intensity is very low. Heavy cloud cover. Temperatures are in the lower/mid 30s which is limited accumulation. Wind chills in the mid 20s.  Mainly wet roads.

We are 10 days into December.  Most days have been above average.

Most of North America is also experiences above normal temperatures so far this month. Notice the lack of blue color.

Historically, since 2013 (last 10 winters) in northern Ohio we've averaged around 12 days below average in December.  last year, most of the below normal days occurred after December 20th.  We remember the brutal cold around Christmas in 2022.  (The complete recap HERE).

Back to today.  Skies will start to clear in spots later this afternoon. Most of the clearing will occur after sundown and overnight tonight.

Gulf moisture stays south as the dominant direction fronts are arriving from is the northwest.  Southwest winds Tuesday with a break from the cold. Limited moisture so clouds will increase Wednesday with no snow or rain.  A slight wind shift (SW to NW) will drop temps briefly Wednesday into the mid 30s.

Beyond that, the week ahead looks very quiet across much of the eastern 2/3rds of the US.

Rainfall forecast is well below normal across much of the mid-west.

Snowfall is virtually non-existent through next Sunday possibly longer.

Next front should pass at the earliest late Sunday December 17 or early Monday of next week.  Cold air behind this front looks brief. Limited moisture so rain and/or snow looks brief and light.

West to east flow across the central US reestablishes itself the week before Christmas

Why is mid December shaping up to be relatively quiet and snow-free for the mid-west? Extremely strong jet stream off of eastern Asia due to late November ridge of high pressure over central Asia and its interaction with the Himalayan Mountains.
The strong Pacific jet keeps the flow of Pacific air going into the western US. Without any strong storm systems across the continent to steer cold from the north, the flow stays west-to-east and fairly uneventful.

Milder trend looks to continue into Christmas week along with an active southern storm track.

We are still watching the high potential for COLD after the first of the year.