We have had several very light snow events this season with only one of them, the 0.2 inches measured last Friday, being enough to completely cover flat surfaces. Those two-tenths of an inch eventually melted with the warmer weather on Sunday, but previous to that, the other light snow recorded in Fargo Moorhead disappeared with temperature staying below 32 degrees. How is that possible?
Sublimation is the process of a solid (snow) transitioning to a gas (water vapor), without first going through the liquid phase (melting). Sublimation occurs all winter, but the amount of snow loss through this process is minimal and it generally goes unnoticed, especially once a deeper snow pack overtakes the region. But when snow amounts are exceptionally light, then this subtle loss of snow on the ground or on your driveway can be quite noticeable.
The opposite of sublimation is deposition and that is the process of a gas changing to a solid and that is the method in which frost forms during our cold season.
Fargo Moorhead residents are waking up this morning to another brown Thanksgiving. Lack of snow cover on Thanksgiving Day has become very common place in recent years. Since the turn of the century there have been only two Thanksgivings with snow on the ground. One was just last year when a bit over two inches of snow fell with a stiff north wind during the day.
Thanksgiving 2012 was probably the worst travel day on Thanksgiving Day itself since 1993 when 8 inches of snow fell that year on the holiday. Besides 2012, the only other Thanksgiving this century with snow on the ground was back in 2010 when a 12 inch snow event occurred a couple of days before Thanksgiving giving us a snow depth of 8 inches on the holiday. That was the most snow on the ground on the fourth Thursday in November since 1996.
Although very few Thanksgivings in the past decade have been white, several of them turned white before the long holiday weekend was completed.
The average high today is 31 degrees. The average high will stay below freezing until March 8 when that average will finally be back to 32 degrees. During the three principle months of winter, December through February, Fargo Moorhead averages 18 days with a high temperature above freezing.
n four out of the last five winters, we have recorded a below average number of melting days. The one exception was during the winter of 2011-2012 when on 47 of the 91 days that winter the high temperature was above freezing. That is the most of any winter on record. Of note, the other four of the past five winters in total had only recorded 47 days above freezing, an example of how unique the winter of 2011-2012 was for warmth.
The record lowest number of winter days above freezing is two such days that occurred during the brutal winter of 1978-1979.
Last year, today was a rare snowy Thanksgiving Day. Since 1950, there had only been four Thanksgivings with more than one inch of snow falling on the holiday, meaning last year made it five. Unlike this year, there had been several previous snowfalls before that event, but the one a year ago was the first of the season that created nasty travel conditions around Fargo Moorhead.
A bit over two inches fell with a strong north wind lowering visibility and with temperatures going from above to below freezing, the roads became quite icy. This year, Thanksgiving falls as late as it can on November 28. Since records began in 1881, measurable precipitation falls on any given November day about 20% of the time, but those odds increase as the month progresses. The period of this month with the highest historical chance of precipitation are the 25, 26 and 27 when nearly 30% of those days have recorded precipitation. Meaning, the later Thanksgiving falls, the higher the chance of slippery roads.
The high temperature has reached 70 degrees or warmer in Fargo Moorhead during the month of November 16 times since records began in 1881. The last 70 degree November day recorded locally was back on November 8, 2006. That was also the 2nd highest temperature recorded during the month of November behind the November record of 74 degrees set on November 1, 1990.
The latest 70 degree high was on November 10, 1909 then the high was right at 70 degrees. There has been four years when the high reached 70 degrees two times during the month of November, those were in 1999, 1975, 1903 and 1887. The average maximum high during the month of November is 59 degrees, meaning the 61 degree high last Wednesday at Hector Int’l was right near that average.
If you are curious, our average first 60 degree day of spring does not arrive until April 3.
Very little snow has been seen around Fargo Moorhead this season. Unusual? Not at all. In fact our average first 1 inch snow fall is on November 13. We average 7.9 inches in the month of November, but in more years than not, that average is derived from snow events during the 2nd half of November, not the first.
The snowiest winter on record in Fargo Moorhead was back in the 1996-1997 cold season when 117.0 inches of snow was recorded. The first measurable snow of that very long winter did not occur until today, November 15 (which also happened to be a Friday) when two inches fell in the first initial wave of a three day snow storm that eventually brought blizzard conditions to the area over that weekend. By Monday morning, 15.5 inches of snow had fallen. By the end of the month 26.4 inches of snow had fallen on the city.
The odds of a repeat are of course extremely low, but snow will come eventually, it always does.
Both November and December average 18 cloudy days. Because November is one day shorter, it gets listed as the cloudiest month of the year. Yet, that technicality should not take away from the fact that both months tend to be very gray. Plus, when you add the affect of a low sun angle and the short days, many people will have at least some symptoms of Seasonal Affective Disorder or SAD for short.
Often times what breaks up this cloudy pattern are large arctic high pressure systems that tend to bring in the bitterly cold, yet sunnier weather this area often experiences in late December through February. But until then, there will likely be far more cloudy days than sunny ones as this area will tend to be near the storm track for the next several weeks keeping the sky full of clouds and gloom.
I have been asked on more than one occasion in the past week if we will be experiencing any “Indian Summer” this autumn. By definition “Indian Summer” is an extended period of above average temperatures in mid to late autumn. Plus, most individuals only consider true “Indian Summer” to occur only after the first killing frost of the season.
If we use the second part of the definition it is highly unlikely this area will experience another extended period of warm weather before winter as such weather is unusual in this area this late in the year. But if you only consider “Indian Summer” to be period of warm weather in autumn, then we did have a nice stretch during the first half of October. Such weather does not occur every year and such conditions should never be expected.
Yet, when it does occur, those are the days that nearly everyone agrees are the some of the most pleasant weather we experience.
The average temperature in August is roughly 70 degrees, in September that fell to near 60 degrees and this month the average temperature plunges into the middle 40s. In November the average temperature is just 29 degrees and we are in the grips of winter in December with an average temperature only in the middle teens.
Although the first frost of the season occurs in September in three out of four years, it is in October that it becomes obvious that winter is coming. October is also when we often record our first snow flakes of the year. Although the average first measurable snow does not occur until October 31, trace amounts are often observed earlier in the month. The average snow fall in October is a mere 0.7 inches, with the average rainfall being 2.15 inches. Of course all these are averages and our year to year variability is quite high.
You only have to look back at the storm system from this past weekend to know that it only takes one storm to throw the average out the proverbial window.