The weather has certainly been cold in recent days, but locally, we have been nowhere near any record low. The record lows this time of year tend to be in the -30 to -25 degree range. One state that has set numerous record lows recently has been Oregon. An automatic temperature gauge in the Horse Ridge nature area just east of Bend, Oregon dropped to 41 degrees below zero on Sunday morning.
That same morning, the residents of Lakeview, OR, in the far south central portion of the state, woke up to a temperature of -27 degrees. Not only was that a record for the date, it was also an all-time record low for the city. That surpassed the previous coldest temperature on record of -22 set back in February 1933 and January 1937. Perhaps equally impressive was Eugene on the western side of the Cascades dropping to -10, just two degrees shy of their all-time coldest reading and Astoria, on the Pacific coast dropping all the way down to 13 degrees for a daily record low.
December marks the beginning of climatological winter meaning we can take a look at the weather statistics for the just completed autumn season. Both October and November finished with temperatures slightly below average, but because September was very mild, the season as a whole finished with an above average temperature.
The average temperature from September 1 through November 30 was 45.8 degrees which is 1.3 degrees above normal. September 2013 you may recall was the 5th warmest on record with an average temperature over 5 degrees above average, but since early October temperatures have trended cooler. Although, November was a dry month, both September and October were exceptionally wet. In total, 8.97 inches of rain and melted snow fell during the past three months.
That ranked Autumn 2013 as the 7th wettest on record.
The average temperature last month was 28.2 degrees which is 0.6 degrees below the current 30 year average. Although not an exceptionally cold month, it was the coldest November in Fargo Moorhead since 2003. Fargo Moorhead had recorded 9 straight above average Novembers until this year. Not only temperatures finished below average last month, but precipitation did as well.
In total, only 0.40 inches of rain and melted snow was recorded in November. That is well below the average of 1.00 inch. Our cooperative observer in north Moorhead measured 0.3 inches of snow last month. The average November snowfall is 7.9 inches. That ranked November 2013 as the 9th least snowiest November since 1890.
In recent years 2006 with just 0.2 inches and 1999 with no measureable snow ranked lower.
Another November has come and gone with very little snow falling in Fargo Moorhead. From 1985 through the year 2000 snowfall in November was common and often abundant. More than 50% of the years during that stretch recorded more than 10 inches of snow. But since the turn of the century, November snow became much less common.
Since 2001 there has been only two years with above average snow in November. Those two years were in 2001 and in 2010. Including this year, there have been seven years in that period with less than 1 inch of snow. Not only have recent Novembers been low on snow, but also, low on rain. Last month was our 5th straight November with below average precipitation.
Decembers, on the other hand, have tended to be quite wet in recent years leading to spring flooding in 2009, 2010 and 2011 reminding us that the weather can and does change quickly in this area.
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.
This is usually the time of year that we record the first below zero low temperatures of the season. It is also no coincidence that this is also the time of year when we began to record our first snowfalls of one inch or greater. Like most other climate statistics, the first below zero reading varies greatly from year to year.
The earliest below zero low temperature occurred on October 26, 1919 when the low dropped to -4 degrees. The latest first negative of the season was back in 1987 when our first negative temperature did not occur until December 31. The average date is sandwiched in between those two extremes on November 28. The average last below zero day in spring is on March 11.
The overall average number of days below zero during our cold season is 48, with ten of those days recording both a negative high and low.
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.