As Christmas gets closer everyone always wonders if we are going to get the proverbial white Christmas. Unfortunately, if you look at Denver and Thornton weather history, the chances aren’t all that good but it also depends on what you define as a white Christmas.
If to you a white Christmas means having actual snowfall on Christmas Day the chances aren’t that good. But, if simply having snow on the ground suffices, the chances improve considerably.
The Earth at the Winter Solstice. The Northern Hemisphere sees their shortest day of the year while the Southern Hemisphere gets its longest. (NASA)
Astronomical winter arrives in Thornton tonight and with the solstice also comes the shortest day of the year.
Winter officially begins at 9:49pm today. The Winter Solstice occurs when the North Pole is tilted at its furthest from the sun – 23.5 degrees away. This results in the shortest day of the year in the Northern Hemisphere.
Here in Denver, with sunrise at 7:17am and sunset at 4:39pm, our day today is 9 hours, 21 minutes and 14 seconds long. Tomorrow it will be one second longer and each day from now through to the Summer Solstice in June will get gradually longer as well.
While we have a short day today, it is nothing like what will be experienced in the Arctic Circle. Areas north of there to the North Pole will have no direct sunlight at all. Conversely, areas south of the Antarctic Circle toward the South Pole will have 24 hours of daylight and have a midnight sun.
Did you know that there is a difference between the astronomical seasons that we are discussing here and meteorological seasons?
Meteorological seasons differ slightly and are geared toward matching the calendar with the annual temperature cycle. This is done primarily for meteorological observing and forecasting and in many ways it is more logical than the astronomical seasons.
For the Northern Hemisphere, the meteorological spring covers the months of March, April and May. Summer brings the hottest months of the year and so meteorological summer is June, July and August. Meteorological fall then is September, October and November followed by the coldest months of December, January and February as meteorological winter.
White Christmas probability map for the contiguous United States. Click for larger view. (NOAA)
With our most recent snowstorm, the Colorado Front Range is likely to enjoy a white Christmas (defined as 1 inch of snow on the ground on Christmas Day). Other locations in the United States of course are not quite so lucky and historically, Colorado can be quite hit or miss.
Below is the latest narrative from NOAA. To the right is a probability map – click it to view full size.
Minnesota. Maine. Upstate New York. The Allegheny Mountains of Pennsylvania and West Virginia. Practically anywhere in Idaho. And of course, the Rockies or the Sierra Nevada Mountains. These are the places where weather history suggests you want to be if you’re looking for the best chance of a white Christmas.
The map at right shows the historic probability of there being at least 1-inch of snow on the ground in the Lower 48 states on December 25 based on the latest (1981-2010) U.S. Climate Normals from NOAA’s National Climatic Data Center. Dark gray shows places where the probability is less than 10 percent, while white shows probabilities greater than 90 percent.
The 1981–2010 Climate Normals are the latest three-decade averages of several climatological measurements. This dataset contains daily and monthly Normals of temperature, precipitation, snowfall, heating and cooling degree days, frost/freeze dates, and growing degree days calculated from observations at approximately 9,800 stations operated by NOAA’s National Weather Service.
While the map shows the climatological probability that a snow depth of at least one inch will be observed on December 25, the actual conditions this year may vary widely from these probabilities because the weather patterns present will determine the snow on the ground or snowfall on Christmas day. These probabilities are useful as a guide only to show where snow on the ground is more likely. For prediction of your actual weather on Christmas Day, check out your local forecast at Weather.gov.
You can locate Normals data for the observing station closest to you using the NCDC’sinteractive map.
If you would like to keep track of the snowfall across the United States on a daily basis, see the National Operational Hydrologic Remote Sensing Center’s National Snow Analyses. For a more detailed assessment of the probability of a white Christmas as well as documentation of the methodology used to calculate the map’s underlying climatological statistics, see the scientific paper, White Christmas? An Application of NOAA’s 1981-2010 Daily Normals, by NCEI scientists and published in the Bulletin of the American Meteorological Society. You can also download a spreadsheet to see the full list of stations and their historic probabilities.
This post was adapted from an article first published by the National Climatic Data Center. It was first published on December 11, 2013, and is reviewed each year and updated as needed.
Mild, dry conditions started the month of November 2015 in Thornton. That however soon gave way to colder temperatures and moisture in the form of snow, something that repeated itself multiple times during the month.
The first three days saw temperatures well above normal and in the 70s with no precipitation. That changed however with our first snowfall of the season coming on the 5th of the month.
The balance of the month was an active one as a series of troughs moved through and cold fronts dug in from the north. A general pattern of a few mild days followed by a few unsettled days was the pattern. By the time all was said and done, the month more than made up for the lack of snow in October.
In terms of temperatures, Thornton’s overall temperature for the month was 36.9 degrees. Out at DIA where Denver’s official records are kept, the reading was a good bit warmer at 38.5 degrees. While that meant the Mile High City was 0.2 degrees above average, Thornton was clearly a good bit cooler than normal.
Temperatures in Thornton ranged from a high of 75.5 degrees on the third of the month down to a low of 6.7 degrees on the morning of the 27th. DIA saw a maximum of 75 degrees and a minimum of 3 degrees on those same dates.
Precipitation was well above the November average of 0.61 inches at both locations. Thornton saw 1.65 inches of liquid precip while Denver bested us with 2.13 inches.
Snow was the primary source of precipitation for the month. Thornton recorded a very healthy 14.5 inches of the white stuff. The airport lagged with 11.3 inches. Both were well above the November average of 8.7 inches.
Thornton, Colorado’s November 2015 Temperatur?e Summary. (ThorntonW?eather.com?)Thornton, Colorado’s November 2015 Precipitat?ion Summary. (ThorntonW?eather.com?)
From the National Weather Service:
CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
1147 AM MST TUE DEC 1 2015
...................................
...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF NOVEMBER 2015...
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2015
WEATHER OBSERVED NORMAL DEPART LAST YEAR`S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 80 11/08/2006
LOW -18 11/29/1877
HIGHEST 75 11/03 73 2 72 11/29
11/01
LOWEST 3 11/27 -6 9 -14 11/13
AVG. MAXIMUM 51.2 52.1 -0.9 50.6
AVG. MINIMUM 25.7 24.5 1.2 21.8
MEAN 38.5 38.3 0.2 36.2
DAYS MAX >= 90 0 0.0 0.0 0
DAYS MAX <= 32 5 2.3 2.7 5
DAYS MIN <= 32 24 23.4 0.6 22
DAYS MIN <= 0 0 0.6 -0.6 4 PRECIPITATION (INCHES) RECORD MAXIMUM 3.21 1946 MINIMUM T 1899 1901 1949 TOTALS 2.13 0.61 1.52 0.76 DAILY AVG. 0.07 0.02 0.05 0.03 DAYS >= .01 11 4.7 6.3 6
DAYS >= .10 6 1.6 4.4 3
DAYS >= .50 1 0.0 1.0 0
DAYS >= 1.00 0 0.0 0.0 0
GREATEST
24 HR. TOTAL 0.88 11/04 TO 11/05
SNOWFALL (INCHES)
RECORDS
TOTAL 11.3 8.7
RECORD NOVEMBER 42.6 1946
DEGREE_DAYS
HEATING TOTAL 789 801 -12 857
SINCE 7/1 1090 1382 -292 1254
COOLING TOTAL 0 0 0 0
SINCE 1/1 877 769 108 701
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 11/05 10/07
LATEST 05/05
....................................................
WIND (MPH)
AVERAGE WIND SPEED 10.4
RESULTANT WIND SPEED/DIRECTION 3/225
HIGHEST WIND SPEED/DIRECTION 46/350 DATE 11/17
HIGHEST GUST SPEED/DIRECTION 57/290 DATE 11/18
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.40
NUMBER OF DAYS FAIR 11
NUMBER OF DAYS PC 14
NUMBER OF DAYS CLOUDY 5
AVERAGE RH (PERCENT) 55
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 1 MIXED PRECIP 0
HEAVY RAIN 2 RAIN 3
LIGHT RAIN 3 FREEZING RAIN 0
LT FREEZING RAIN 2 HAIL 0
HEAVY SNOW 1 SNOW 8
LIGHT SNOW 11 SLEET 0
FOG 13 FOG W/VIS <= 1/4 MILE 3
HAZE 5
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
The month of December brings with it the official start of winter and oftentimes, colder and snowier weather conditions. It however can also offer unseasonably warm temperatures and bone dry conditions.
Overall December’s monthly mean temperature of 30.0 degrees (1981 – 2010 averages) makes it our coldest month. Snow is always on everyone’s mind this time of year but December is only our 3rd snowiest month behind March and November with an average of 8.5 inches of the white stuff.
We closed out November quite wet and chilly and that is expected to continue into the first part of December. Long term models then point to a continuation of above normal precipitation but near normal temperatures.
A mild October allowed for plenty of outdoor opportunities including amazing sunrises like this one in Thornton along the South Platte River. (Tony’s Takes)
Thornton’s October was an unusually warm one with daytime highs more what we would expect in September. It would also have been a dry one were it not for three days of healthy rainfall in the latter third of the month.
The overall average temperature for the month in Thornton was 54.4 degrees. Out at Denver International Airport where Denver’s official readings are taken, the average was a good bit warmer at 56.5 degrees. The 30 year historical average for October is 50.9 degrees so both locations were considerably warmer than normal.
Temperatures in Thornton ranged from a maximum of 86.8 degrees on the 11th down to 30.5 degrees on the morning of the 28th. Denver’s high and low came on the same dates at 87 degrees and 28 degrees respectively. The high reading on the 11th was a record high for the date.
In terms of precipitation, 1.54 inches fell in Thornton’s rain bucket. Denver bested us with 1.76 inches. Both beat the October average of 1.02 inches.
Snowfall was non-existent during the month. On average the Mile High City sees 4.0 inches of the white stuff in October.
Thornton, Colorado’s October 2015 temperatur?e summary.Thornton, Colorado’s October 2015 precipitation summary.
From the National Weather Service:
CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
315 PM MST SUN NOV 1 2015
...................................
...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF OCTOBER 2015...
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2015
WEATHER OBSERVED NORMAL DEPART LAST YEAR`S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 90 10/01/1892
LOW -2 10/29/1917
HIGHEST 87 10/11 83 4 83 10/15
LOWEST 28 10/28 22 6 29 10/27
AVG. MAXIMUM 70.1 65.3 4.8 69.5
AVG. MINIMUM 42.8 36.6 6.2 40.7
MEAN 56.5 50.9 5.6 55.1
DAYS MAX >= 90 0 0.0 0.0 0
DAYS MAX <= 32 0 0.4 -0.4 0
DAYS MIN <= 32 1 8.5 -7.5 4
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 4.17 1969
MINIMUM T 1934
TOTALS 1.76 1.02 0.74 0.52
DAILY AVG. 0.06 0.03 0.03 0.02
DAYS >= .01 6 5.3 0.7 5
DAYS >= .10 3 2.4 0.6 2
DAYS >= .50 2 0.5 1.5 0
DAYS >= 1.00 0 0.1 -0.1 0
GREATEST
24 HR. TOTAL 0.87 10/20 TO 10/21
SNOWFALL (INCHES)
TOTAL 0.0 4.0
RECORD OCTOBER 31.2 1969
DEGREE_DAYS
HEATING TOTAL 274 440 -166 299
SINCE 7/1 301 581 -280 394
COOLING TOTAL 16 5 11 0
SINCE 1/1 877 769 108 701
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/28 10/07
LATEST 05/05
..................................................
WIND (MPH)
AVERAGE WIND SPEED 8.8
RESULTANT WIND SPEED/DIRECTION 2/203
HIGHEST WIND SPEED/DIRECTION 29/010 DATE 10/27
HIGHEST GUST SPEED/DIRECTION 40/160 DATE 10/02
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.60
NUMBER OF DAYS FAIR 6
NUMBER OF DAYS PC 15
NUMBER OF DAYS CLOUDY 10
AVERAGE RH (PERCENT) 53
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 2 MIXED PRECIP 0
HEAVY RAIN 0 RAIN 3
LIGHT RAIN 6 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 0
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 9 FOG W/VIS <= 1/4 MILE 3
HAZE 6
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
The weather during the month of November in Denver metro area can offer just about anything. While it is normally a quiet month, it can be prone to extremes.
November is Denver’s second snowiest month and major snowstorms are not entirely uncommon. However conditions can also be quite dry.
Temperatures during the month continue to cool as we get closer to winter and by the end of the month the low temperatures routinely dip to 20 degrees or below. At times it can in fact bring conditions more like what we see in January.
Temperature – U.S. Winter Outlook: 2015-2016. Click for larger view. (NOAA)
NOAA’s Climate Prediction Center released their 2015-2016 winter outlook this morning and while a strong El Niño will play a factor in some parts of the nation, its effects here are less clear.
As we have written about before, Colorado’s geographical location well inland, shelters it some from the effects of warm, Pacific waters. Overall snowfall in Colorado during El Niño years has not trended greatly one way or another. We have however seen some of our largest storms during El Niño.
NOAA’s outlook shows a pretty typical El Niño situation with some locations of the nation expected to receive copious amounts of moisture. For us, it does point to a bit better chance of a wetter than normal period from December to February.
Read the complete text of NOAA’s outlook below. At the bottom is the video they released to accompany it.
Precipitation – U.S. Winter Outlook: 2015-2016. Click for larger view. (NOAA)
Forecasters at NOAA’s Climate Prediction Center issued the U.S. Winter Outlook today favoring cooler and wetter weather in Southern Tier states with above-average temperatures most likely in the West and across the Northern Tier. This year’s El Niño, among the strongest on record, is expected to influence weather and climate patterns this winter by impacting the position of the Pacific jet stream.
“A strong El Niño is in place and should exert a strong influence over our weather this winter,” said Mike Halpert, deputy director, NOAA’s Climate Prediction Center. “While temperature and precipitation impacts associated with El Niño are favored, El Niño is not the only player. Cold-air outbreaks and snow storms will likely occur at times this winter. However, the frequency, number and intensity of these events cannot be predicted on a seasonal timescale.”
Other factors that often play a role in the winter weather include the Arctic Oscillation, which influences the number of arctic air masses that penetrate into the South and nor’easters on the East Coast, and the Madden-Julian Oscillation, which can impact the number of heavy rain storms in the Pacific Northwest.
The 2015 U.S. Winter Outlook (December through February):
Precipitation Outlook:
Wetter-than-average conditions most likely in the Southern Tier of the United States, from central and southern California, across Texas, to Florida, and up the East Coast to southern New England. Above-average precipitation is also favored in southeastern Alaska.
Drier-than-average conditions most likely for Hawaii, central and western Alaska, parts of the Pacific Northwest and northern Rockies, and for areas near the Great Lakes and Ohio Valley.
Temperature Outlook:
Above-average temperatures are favored across much of the West and the northern half of the contiguous United States. Temperatures are also favored to be above-average in Alaska and much of Hawaii. Below-average temperatures are most likely in the southern Plains and Southeast.
Drought Outlook:
The U.S. Drought Outlook shows some improvement is likely in central and southern California by the end of January, but not drought removal. Additional statewide relief is possible during February and March. Drought removal is likely across large parts of the Southwest, while improvement or removal is also likely in the southern Plains. However, drought is likely to persist in the Pacific Northwest and northern Rockies, with drought development likely in Hawaii, parts of the northern Plains and in the northern Great Lakes region.
While it is good news that drought improvement is predicted for California, one season of above-average rain and snow is unlikely to remove four years of drought,” said Halpert. “California would need close to twice its normal rainfall to get out of drought and that’s unlikely.”
This seasonal outlook does not project where and when snowstorms may hit or provide total seasonal snowfall accumulations. Snow forecasts are dependent upon the strength and track of winter storms, which are generally not predictable more than a week in advance.
NOAA produces seasonal outlooks to help communities prepare for what’s likely to come in the next few months and minimize weather’s impacts on lives and livelihoods. Empowering people with actionable forecasts and winter weather tips is key to NOAA’s effort to build a Weather-Ready Nation.
NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter, Instagram and our other social media channels.
Updated | Federal weather forecasters released their winter outlook Thursday, and it doesn’t look good for drought-stricken northern California, Oregon and Washington state. A strong El Niño this winter is predicted to intensify the Western drought through at least January, the National Oceanic and Atmospheric Administration announced. Earlier this week, NASA released a new image of… Continue reading El Niño Won’t Relieve West’s Drought, NOAA Predicts→
With the first full month of fall here, October usually brings one of the quietest weather months in the Denver area with plenty of mild, sunny days and clear, cool nights.
October is historically the second sunniest month and conditions are generally calm.
However we also will usually see our first taste of winter during the month with the first freeze and first snowfall of the season. Temperatures as well will start to drop and by the end of the month the average nighttime lows are below freezing.
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Weather, natural disasters & climate news and information.
The month of December brings with it the official start of winter and oftentimes, colder and snowier weather conditions. It however can also offer unseasonably warm temperatures and bone dry conditions.
The weather during the month of November in Denver metro area can offer just about anything. While it is normally a quiet month, it can be prone to extremes.
With the first full month of fall here, October usually brings one of the quietest weather months in the Denver area with plenty of mild, sunny days and clear, cool nights.