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All posts by Thornton Weather
October 15 to October 21: This week in Denver weather history
Snow and wind are two common conditions we see this time of year and our look back at this week in Denver weather history certainly has those type of events. Also notable is a surprising October hail storm 13 years ago that went into the books as one of the costliest in history.
From the National Weather Service:
13-16
In 1873…smoke from several large forest fires in the mountains made the air very hazy in the city.
15
In 1871…a terrible wind occurred during a snow storm in the foothills above Boulder. Damage was minor.
In 1878…high winds reached sustained speeds of 60 mph at times.
In 1911…post-frontal northwest winds were sustained to 41 mph with gusts to 43 mph.
In 1948…strong winds struck the Boulder area. Winds averaged 50 mph at Valmont just east of Boulder. Wind gusts in excess of 60 mph were recorded at the Boulder airport. Wind gusts to 40 mph briefly reduced the visibility to 1 1/2 miles in blowing dust at Stapleton Airport.
In 1980…a rare October tornado touched down in Boulder… Damaging a vocational training building and throwing three nearby cars together damaging them extensively. A mile and half away several camper vehicles were thrown 200 feet. The storm also produced 1 inch diameter hail in the Boulder area.
15-16
In 1928…a thunderstorm produced hail shortly after midnight on the 15th. Rain changed to snow by evening. Through the afternoon of the 16th…the heavy snowfall totaled 7.3 inches in the city. North winds were sustained to 23 mph on the 15th.
In 1984…the heaviest October snowstorm in several years hit eastern Colorado with a vengeance. The storm was known as the “Bronco Blizzard” since it occurred during a nationally televised Monday Night Football game in Denver. One to two feet of snow fell near the foothills in west metro Denver with 2 to 3 feet in the foothills. Wind gusts up to 55 mph whipped the snow into drifts as high as 4 feet. The storm closed schools…roads…and airports. I-70 was closed both east and west of Denver. I-25 was closed south to Colorado Springs. Flights were delayed for several hours at Stapleton International Airport. Power outages were widespread. Snowfall totaled 9.2 inches at Stapleton International Airport where north winds gusting as high as 40 mph caused frequent surface visibilities of 1/4 to 1/2 mile in moderate to heavy snow and blowing snow overnight. The high temperature of only 35 degrees on the 15th was a record low maximum for the date.
15-17
In 1989…an autumn snowstorm hit metro Denver with 2 to 6 inches of snow. Snowfall totaled 4.4 inches at Stapleton International Airport where the maximum snow depth on the ground was only 3 inches due to melting and north winds gusted to 25 mph on the 15th. The heavy wet snow caused leafy branches to sag onto power lines…resulting in a number of power outages. Five thousand homes were blacked out in Boulder on the 16th. Up to a foot of snow fell in the higher foothills with 19 inches recorded at Echo Lake.
16
In 1878…high winds reached sustained speeds of 60 mph.
In 1998…one of the costliest hail storms to ever hit metro Denver caused an estimated total of 87.8 million dollars in damage to homes…commercial buildings…and motor vehicles. At the time the storm was ranked as the 7th costliest ever. The hailstorm…rare for so late in the season…began over portions of Arvada…Wheat Ridge…and northwest Denver where mostly pea sized hail accumulated up to a depth of 6 inches near I-70. Several accidents were attributed… At least in part…to the hailstorm. Snowplows had to be called out to clear several city streets. The storm intensified as it moved to the east…into the Denver and Aurora areas. Large hail…up to 2.00 inches in diameter pounded east and southeast metro Denver. Two inch diameter hail fell in the city of Denver and at Buckley Field. Hail as large as 1 1/2 inches was measured in south Denver with 1 inch diameter hail in northern Aurora.
In 1999…upslope conditions produced snow across metro Denver with heavy amounts in the nearby foothills. Snowfall totals included: 9 inches at Eldorado Springs; 8 inches at Genesee… Golden Gate Canyon…Littleton and near Morrison; 7 inches near Nederland; and 6 inches in Louisville. Snowfall totaled 3.6 inches at the site of the former Stapleton International Airport.
16-17
In 1990…strong downslope winds raked the eastern foothills. Wind gusts from 60 to 75 mph were common. Strong winds in metro Denver resulted in wave damage to a dock used to moor several private sail boats at Cheery Creek Reservoir. Damage was confined to the dock and two anchor cables. A northwest wind gust to 43 mph was recorded at Stapleton International Airport.
Continue reading October 15 to October 21: This week in Denver weather history
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October 8 to October 14: This week in Denver weather history
Denver has yet to get a taste of wintry weather this year as we continue what has been a very dry period the last few months. In the past that hasn’t always been the case and our look back at this week in Denver weather history shows that heavy, winter-like snowstorms can and do strike in October.
From the National Weather Service:
7-8
In 1990…the season’s first snow occurred. Snowfall amounts varied from 3 to 7 inches across metro Denver. Snowfall totaled 4.0 inches at Stapleton International Airport where north winds gusted to 29 mph.
8
In 1923…southeast winds were sustained to 44 mph with gusts to 47 mph. The strong winds persisted through the afternoon. The high temperature of 77 degrees was the warmest of the month that year.
In 1975…a wind gust to near 100 mph was recorded in Boulder. Frequent wind gusts to 60 mph were reported along the foothills causing only minor damage. West winds gusted to 45 mph at Stapleton International Airport.
9
In 1910…light smoke from forest fires in the mountains was sighted over the city.
In 1982…northwest winds gusted to 49 mph at Stapleton International Airport.
9-10
In 2005…a major winter storm brought heavy…wet snowfall to the Front Range mountains…eastern foothills…portions of metro Denver…and the Palmer Divide. Snow accumulations ranged from 8 to 26 inches with drifts from 3 to 4 feet in places. The heaviest snow occurred to the east and southeast of the city…closing most major highways in that area…including I-70 from Denver to Limon. The Red Cross opened four shelters for people who were stranded along I-70 in eastern Colorado. Since many trees had not yet shed their leaves…the storm caused significant tree damage. One woman in Denver was killed when a tree branch… 8 to 10 inches in diameter…snapped under the weight of the heavy…wet snow and struck her as she was shoveling her driveway. Xcel Energy reported power outages to about 35 thousand customers. Several incoming flights were delayed at Denver International Airport. Snow totals included: 16 inches in the foothills near Boulder…12 inches at Genesee and near Golden…22 inches near Watkins…19 inches near Bennett…17 inches southeast of Aurora…14 inches near Parker…13 inches near Castle Rock…12 inches in centennial… 11 inches in Parker…and 10 inches at Denver International Airport and in Littleton. While many areas of metro Denver received heavy snow…others experienced almost entirely rain. This included west and northwest metro Denver…Boulder…and Longmont. Rainfall amounts were significant as storm totals ranged between 1.50 and 2.50 inches. The steady rainfall triggered 3 rockslides in foothills canyons. Two of the slides occurred on State Highway 119 in Boulder Canyon and the longest slide…7 feet in length…on State Highway 74 in Bear Creek Canyon at Idledale. North winds were sustained to around 23 mph with gusts to 31 mph at Denver International Airport on the 9th. The high temperature of only 34 degrees on the 10th was a record low maximum for the date. The low temperature on both days was 32 degrees.
10
In 1901…an evening thunderstorm produced east winds to 43 mph with gusts to 48 mph.
In 1949…strong winds believed to be the worst in Boulder’s history at the time caused over 100 thousand dollars damage in the city. Peak winds were estimated to 85 mph at Valmont…just east of Boulder. High winds also occurred over most of metro Denver and caused damage to trees…window glass…and utility lines. The damage was most pronounced over the northwest metro area…including north Denver and Lakewood. Falling tree branches caused damage to parked autos and houses. Wind gusts to 70 mph were recorded at Stapleton Airport.
In 1964…lightning struck and killed a 13-year-old boy…while he was riding his bicycle along a tree-lined residential street in south Denver. Apparent microburst winds gusted to 54 mph at Stapleton International Airport.
10-11
In 1986…the first significant snowstorm of the season produced 2 to 5 inches of snow over metro Denver with 5 to 10 inches in the foothills west of Denver. Wondervu recorded the most snow from the storm…13 inches. The heavy wet snow caused numerous power outages. The storm was accompanied by strong north winds with gusts to 41 mph recorded on the 10th. The first snowfall of the season totaled 3.1 inches at Stapleton International Airport with only one inch on the ground due to melting. The strong cold front accompanying the storm cooled the temperature from a high of 73 degrees on the 10th to a high of only 33 degrees on the 11th…which was a record low maximum for the date.
10-12
In 1969…the second heavy snowstorm in less than a week dumped nearly a foot of snow across metro Denver and plunged the area into extremely cold temperatures for so early in the season. Snowfall totaled 11.0 inches at Stapleton International Airport. North winds gusting to 26 mph produced drifts up to 2 feet deep. Temperatures dipped from a high of 52 degrees on the 10th to a record low for the date of 10 degrees on the 12th. There was additional damage to trees and power and telephone lines from heavy snow accumulations and icing. Travel was restricted or blocked by drifting snow in both the mountains and on the plains east of Denver.
11
In 1997…damaging winds ahead of an approaching storm system developed in the foothills and spread across metro Denver. Winds gusted to 88 mph at conifer…71 mph at the National Center for Atmospheric Research on the mesa in Boulder… And 53 mph at Denver International Airport. Several trees and street signs were blown down with scattered power outages reported throughout metro Denver. In Arvada…a car window was blown out by a strong wind gust.
In 2013…high winds occurred in and near the Front Range Foothills. Peak gusts included: 85 mph at Rooney Road…84 mph…2 miles south of Marshall; 82 mph at Rocky Flats National Wind Technology Center and Wondervu; 79 mph at the Mesa Lab at NCAR and 75 mph…3 miles south-southwest of Boulder; 73 mph in Superior and 68 mph in Golden. The wind downed trees and power lines. As a result…scattered electrical outages affected 20000 Xcel Energy customers through the morning hours. The main outages affected the cities of Boulder…Golden and Lakewood. Smaller outages were reported in areas of Gold Hill…Ward… Westminster and Wheat Ridge.
Continue reading October 8 to October 14: This week in Denver weather history
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September 2017 weather recap: Month starts warm and dry, ends cool and damp
The month of September 2017 saw significant differences between the start and the end. The first two-thirds of the month were extraordinarily dry with temperatures well above normal. The last 10 days brought a big change though with damp conditions and much cooler conditions.
High pressure dominated the region for the first few weeks of the month. During this period when we normally see cooler temperatures, we instead saw highs oftentimes at or above 90 degrees and a couple of record high readings. Additionally, it was exceedingly dry with Thornton only received 0.03 inches of precipitation through the first 22 days of the month.
Big changes arrived and the last nine days of the month stood it stark contrast to the rest of September. Low pressure and a series of disturbances brought much cooler temperatures and much-needed precipitation, including snowfall in the high country. Seven out of the last eight days saw below normal high temperature readings and enough precipitation fell to push us to just above normal.
Thornton’s overall average temperature for the month came in at 62.4 degrees. This was a full degree cooler than Denver’s long term September average of 63.4 degrees. Out at DIA where Denver’s official measurements are taken, it was a good bit warmer with an average temperature of 65.1 degrees.
Temperatures in Thornton ranged from a high of 98.5 degrees on the third and a low of 40.9 degrees on the morning of the 29th. Denver saw their high of 97 degrees on the third as well and their coldest reading of 40 degrees on the 20th.
Two record high temperatures were officially set or tied for the Mile High City. The high temperature of 97 degrees on the third tied the record high for the date. A reading of 92 degrees on the 21st set a new record high for that date.
In terms of precipitation, Denver averages 0.96 inches during September. Thornton tallied 1.05 inches in the rain bucket while Denver bested us with 1.26 inches.
Click here to view Thornton’s September 2017 climate report.
From the National Weather Service:
CLIMATE REPORT
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
244 AM MDT SUN OCT 1 2017
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...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2017...
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2017
WEATHER OBSERVED NORMAL DEPART LAST YEAR`S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 97 09/03/2017
09/06/2013
09/05/2013
LOW 17 09/29/1985
HIGHEST 97R 09/03 91 6 93 09/05
LOWEST 40 09/20 35 5 37 09/10
AVG. MAXIMUM 79.0 78.5 0.5 82.3
AVG. MINIMUM 51.3 48.3 3.0 49.7
MEAN 65.1 63.4 1.7 66.0
DAYS MAX >= 90 9 3.4 5.6 6
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.8 -0.8 0
DAYS MIN <= 0 0 0.0 0.0 0 PRECIPITATION (INCHES) RECORD MAXIMUM 5.61 2013 MINIMUM T 1892 1944 TOTALS 1.26 0.96 0.30 0.28 DAILY AVG. 0.04 0.03 0.01 0.01 DAYS >= .01 6 6.5 -0.5 4
DAYS >= .10 2 3.3 -1.3 1
DAYS >= .50 1 0.6 0.4 0
DAYS >= 1.00 0 0.1 -0.1 0
GREATEST
24 HR. TOTAL 0.83 09/23 TO 09/23 09/12 TO 09/12
SNOWFALL (INCHES)
RECORDS
TOTAL 0.0
TOTALS 0.0 1.3
DEGREE_DAYS
HEATING TOTAL 122 125 -3 64
SINCE 7/1 130 141 -11 79
COOLING TOTAL 131 76 55 99
SINCE 1/1 880 764 116 861
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
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WIND (MPH)
AVERAGE WIND SPEED 9.6
RESULTANT WIND SPEED/DIRECTION 2/165
HIGHEST WIND SPEED/DIRECTION 40/020 DATE 09/19
HIGHEST GUST SPEED/DIRECTION 48/030 DATE 09/19
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.50
NUMBER OF DAYS FAIR 9
NUMBER OF DAYS PC 15
NUMBER OF DAYS CLOUDY 6
AVERAGE RH (PERCENT) 48
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 0 MIXED PRECIP 0
HEAVY RAIN 1 RAIN 1
LIGHT RAIN 10 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 0
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 8 FOG W/VIS <= 1/4 MILE 1
HAZE 10
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.