Today not only marks the last day of the month, but in weather also the last day of autumn, meaning tomorrow will be the beginning of climatological winter. Any forecast you may hear for winter is always referencing the three coldest months of the year, December, January and February.
Granted, our winter goes well beyond those three months, but even locally, those are the core months of the winter season. The average temperature for the next three months in Fargo Moorhead is 12.6 degrees. Four out of the last five winters finished with an average temperature below that mark, the exception of course was last year when we recorded the warmest winter on record. Although our seasonal average snowfall is 50.1 inches, the three principal months of winter the average snowfall is 29.4 inches and the average liquid equivalency (rain and melted snow) is 2.14 inches.
Averages are just that, averages, and the weather the next 90 days will likely be highly variable.
Although Fargo Moorhead has not recorded much snowfall this season, we are only running a couple of inches below average. Grand Forks has also observed only a few light snow events this season. But much of the northern tier of North Dakota have recorded above average snow fall this month and parts of north central and northwestern North Dakota well above. Williston has received 16 inches this month, twice their November average.
Yet, just north of there, the snow totals have been even higher. Both Regina and Estevan, Saskatchewan have both had record breaking November snowfalls. Regina has recorded 23 inches of snow besting the old record for the month of 21.1 inches. That also happens to be more snow than they received all of last winter when just 20.5 inches fell. Estevan has recorded even more snow with 25.7 inches being measured this month which also exceeds their total from last winter by 1.1 inches.
Tomorrow is the last day of the season with an average high of 32 degrees for warmer until next spring. Then for the next 104 days the average high will be below 32 degrees in Fargo Moorhead. Of course that does not mean we will not be seeing any melting during this stretch, in fact, historically we average 20 days with a high at or above 32 degrees during December, January and February, the three principle months of winter.
Although some winters we have only recorded a handful of above freezing days, last year the official high at Hector Int’l reached or exceeded the freezing mark on 53 occasions from December 1 through February 29. That was more than the previous four winters combined. You may remember that all four of those winters finished colder than average and last winter was the warmest on record.
That is another great example of the high variability from year to year this region experiences.
The iconic image of Thanksgiving is sometimes represented by a sleigh drawn by horses ferrying a family through the woods to grandmother’s house for dinner. Of course without snow covering the ground, that sleigh would not go very far. The problem with that image, even locally, with one of the coldest climates in the lower 48 states, is that snow cover on Thanksgiving Day tends to be very light or none existent.
In Fargo, there has only been one Thanksgiving this century with snow covering the ground and that was two years ago when the official snow depth was 7 inches. Previous to that year, to enjoy a true sleigh ride experience you would need to go back to Thanksgiving 1996 when two snow storms left us with a snow pack of 13 inches that year.
Other recent notable snow covered Thanksgivings include 1993 with 12 inches on the ground (with 8 inches falling that day) and in 1985 and 1977 with over a foot on the ground.
The winter of 2011-2012 was the warmest on record in Fargo Moorhead. It was nearly 10 degrees above the current 30 year average.
There is no doubt that the overall pattern last winter was a mild one. The upper level wind pattern was consistently from the west allowing mild Pacific air to dominate the season with only a couple of intrusions of Arctic air disrupting that pattern. But another very important element to the warmth was our lack of snow cover. This past week has been a prime example.
Fargo Moorhead missed the big storm earlier this month that left a significant snow cover over central and northern North Dakota. The eight days following the storm the average high in Fargo was 40 degrees, but in usually warmer Bismarck with a snow cover the average high was just 32 degrees. Even Grand Forks with minimum snow from the storm (like Fargo), the nearby snow pack lowered their average to just 33 degrees.
Because the sun angle is so low this time of year making it difficult to melt much snow, an early season snow storm can in turn, influence the average temperature for the entire cold season.
Current snow cover over the area.
The Climate Prediction Center (CPC) released an updated winter forecast last Thursday. Most of the year they were forecasting a higher than normal probability of a warmer than average winter, but with their latest forecast, they are now predicting a higher than normal probability of a colder than average winter.
Why the change? I can not say for sure, but it is probably because the El Nino the CPC thought was going to form, in turn, has not yet formed and there are significant doubts one will form in the upcoming months. An El Nino, the warming of the equatorial waters in the Pacific Ocean, often brings warmer than average winter temperatures to this area, although, the last El Nino in 2009-2010 did not.
Seasonal weather patterns tend to be dominated by a number of factors, not just one and most of those influences are very difficult or impossible to forecast more than a couple of weeks in advance.
Here is the latest forecast from the CPC.
Measuring snow can often more art than science. On occasion the snow falls straight down and most of the reports in a small area are approximately the same. There is always going to be natural variations, but many times the snow measurements differ because of technique, especially when the wind blows.
Often times we will receive snow totals that may vary by several inches just within Fargo Moorhead. When the wind blows, it tends to blow the snow off your roof and deposit it near your house, so a two inch event often gets measured as 4 inches of snow, especially if the report comes from the backyard deck.
Although the official measurement could be considered an educated guess at times, our official observer through careful observation and years of experience usually gives a very good estimate to our snow fall even for the windiest of events and that total can easily be quite different than what you find on your driveway.
October ranked as the 41st coolest on record in Fargo Moorhead. Although locally last month was not exceptionally cold for our climate, other parts of both North Dakota and Minnesota finished much colder. The National Climatic Data Center (NCDC) released their monthly statistics for last month earlier this week and found that taken as a whole, October ranked in the top 30 coldest on record in both North Dakota and Minnesota.
NCDC ranked October 2012 as the 23rd coldest on record in North Dakota and the 29th coldest on record for the state of Minnesota. The precipitation statistics also varied. Fargo Moorhead record 2.22 inches of rain and melted snow last month, right at the average of 2.15 inches, but taken as a whole, North Dakota recorded the 14th wettest October on record. There were several precipitation events in western and northern North Dakota last month that missed us locally or dropped lighter amounts of precipitation.
Minnesota on the other hand, like Fargo Moorhead finished right near the long term average for precipitation.
After a slow start, the second half of October recorded several snow events that greatly expanded the snow cover over Siberia. Some studies have suggested that October snow cover has some correlation with winter temperatures in the United States, especially areas east of the Rocky Mountains. In October the snow cover can increase anywhere from between 4 to 6 million square miles, an area larger than the United States.
Last year Siberia recorded below average snow cover during the month of October. This year, there has been a significant increase in snow cover and last month ranked as the 11th highest total in the past 45 years. The theory is that the larger the build up of snow in Siberia early in the season, the higher the likelihood that large Arctic air masses will form and eventually move into North America, especially in January and February bringing a colder than average winter.
Of course, this is just one of many possible drivers that could influence the weather patterns during our cold season
Not only is November the beginning of what I like to call our cold season, but it is also the beginning of what could be called our dry season. From November 1 through February 28, Fargo Moorhead only averages 3.14 inches of liquid equivalency (rain and melted snow). That is less than our average precipitation in the month of June (3.90 inches).
The average precipitation in November is 1.00 inch, December 0.83 inches, January 0.70 inches with February being the driest with an average of 0.61 inches. Although last year that stretch recorded a below average 2.15 inches of moisture, our dry season totals in recent years have generally been well above average. From November through February in both 2008-9 and 2009-10 we recorded nearly 5 inches of rain and melted snow during this stretch and that does not include what fell in March.
If you are curious, the current average March precipitation is 1.30 inches which could also be included in our list of dry season months.