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Following the snow, Tuesday to offer up sun but with chilly temperatures.

Tuesday, April 20th, 2021 5:08am MDT

Thornton received 3.9 inches from last night’s snow and, thankfully, it is much lighter than the stuff that fell last time. The fast-moving storm has moved out and the sun will return in its wake but it will remain quite chilly.

Mostly sunny to sunny skies will be with us this morning then a few clouds arrive later in the day. Overall conditions will be calm and dry. High temperatures will top out near the 40 degree mark, about 20 degrees below normal.

Tonight, cloud cover will increase and overnight lows will dip to the low to mid-20s.

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Monday brings another snowstorm to Thornton, Winter Weather Advisory issued

Monday, April 19th, 2021 5:05am MDT

This time of year everyone is getting quite weary of cold and snow but as Mother Nature is set to demonstrate, we are far from done with wintry conditions. The day starts out nice enough but the afternoon into tonight sees things change considerably.

Mostly sunny skies great us at dawn this morning. Clouds will be increasing through the morning and early afternoon as our next storm system makes itself felt. Winds will be becoming breezy and out of the northeast by mid-morning.

Early afternoon introduces precipitation, initially as a light, rain snow mix. After reaching a high in the low to mid-40s, temperatures will be dropping after noon. As they do, precipitation will change to all snow and increase in coverage. By about 4:00pm it will become widespread and last until midnight.

A quick 3 to 6 inches will be possible during that time. After midnight, the snow will taper off and skies will begin to clear. Overnight lows will be quite cold and into the teens.

A Winter Weather Advisory will be in effect from 3:00pm this afternoon to 3:00am early tomorrow morning. The evening commute may feel some effects from the start of the snow and conditions during the evening will degrade. All the latest on our Winter Weather Briefing Page.

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April 18 to April 24: This week in Denver weather history

Sunday, April 18th, 2021 5:07am MDT

This Week in Denver Weather History

April can truly bring just about any kind of weather to the Denver area.  From blizzards and snowstorms that are more common in the deepest part of winter to severe spring-like weather like tornadoes and hail, we can and do see it all.  Our look back at this week in Denver weather history shows all of those conditions and more.

17-18

In 1878…the wind blew violently all day on the 17th with a maximum sustained velocity of 40 mph.  Dust hung over the city like a cloud.  The relative humidity was zero nearly all day.  A terrific gale blew overnight.  There was much damage to buildings…signs…fences…etc.  Some wind gusts were so strong as to jar buildings to their foundations.  The station anemometer recorded sustained winds to 50 mph with higher gusts before it was damaged by the winds.  The winds moderated during the day on the 18th and ended at sunset.

In 1894…post-frontal rain changed to snow on the 17th around sunrise and continued through 9:00 am on the 18th. Snowfall totaled 10.5 inches…but most of the snow melted as it fell.  The high temperature warmed to only 35 degrees on the 17th after a high of 76 on the 16th.  Northeast winds were sustained to 30 mph with gusts to 32 mph on the 17th.

In 1998…more spring snow fell across metro Denver and in the foothills.  Snowfall totals included:  11 inches at Golden Gate Canyon; 10 inches at Highlands Ranch; 9 inches at Elizabeth; 8 inches at Broomfield and Morrison; and 7 inches at Chief Hosa…Evergreen…Littleton…and Sedalia. Snowfall totaled only 3.2 inches at the site of the former Stapleton International Airport.  North winds gusted to 22 mph at Denver International Airport.

17-19

In 1920…snow fell across the city continuously for 57 hours… From the early morning of the 17th until 11:40 am on the 19th.  The heavy wet snowfall totaled 18.2 inches with the greatest accumulation on the ground of 12 inches.  Winds during the storm were strong with sustained speeds in excess of 27 mph for over 40 consecutive hours…which created near-blizzard conditions.  The highest recorded wind speeds were 44 mph with gusts to 50 mph from the north on the 17th and 39 mph with gusts to 48 mph from the northwest on the 18th.  The strong winds piled the snow into high drifts which stopped all Denver traffic. Railroads were blocked with only one train entering the city on the 19th.  All interurban trains were blocked…as were the 13 trolley lines.  Thus…many workers were unable to get home at night and filled all of the downtown hotels to capacity.  No grocery or fuel deliveries were possible… Except milk and coal to hospitals and to families with babies.  No lives were lost in the city…but several people perished in surrounding districts.  Stock losses were heavy on the plains.  Temperatures during the storm were in the 20’s.

18

In 1877…strong winds blew all day with an average sustained velocity of 36 mph.  The maximum sustained velocity was 60 mph.  No significant damage was reported.

In 1903…northwest winds were sustained to 48 mph with gusts to 53 mph.

In 1936…light dust spread over the city from the east on southeast winds gusting to 25 mph.  The surface visibility was reduced to about 2 miles at times.

In 1940…this date marked the start of the longest period without snow…200 days…through November 3…1940.  A trace of snow fell on both April 17…1940…and November 4…1940.

In 1963…strong winds were prevalent all day across metro Denver.  West-northwest winds gusting to 60 mph produced some blowing dust at Stapleton Airport.

In 1971…a microburst wind gust to 59 mph produced some blowing dust at Stapleton International Airport.

In 1978…high winds caused much blowing dust over the plains. Wind gusts from 80 to 96 mph were reported in Boulder with 80 mph measured on Lookout Mountain.  Northwest winds gusted to 43 mph at Stapleton International Airport.

In 2000…high winds developed in the foothills of Boulder County.  Peak wind gusts included 71 mph at the National Center for Atmospheric Research Mesa Lab near Boulder. In Aurora…three workers were injured when strong winds caused a home under construction to partially collapse. Two received minor injuries…while the third worker had to be hospitalized with severe back injuries.  South winds gusted to 47 mph at Denver International Airport.

In 2002…strong northeast winds behind a cold front gusted to 53 mph at Denver International Airport where some blowing dust briefly reduced the visibility to 3 miles.

18-19

In 1884…a major storm dumped 13.8 inches of snowfall on downtown Denver.  Most of the snow…10.0 inches…fell on the 18th.  Light rain on the early morning of the 18th changed to heavy snow at 8:00 am and became light after 2:00 pm but continued until 4:00 am on the 19th.  The snow melted nearly as fast as it fell.  There were only 3 inches on the ground early on the morning of the 19th.

In 1941…heavy snowfall totaled 8.4 inches over downtown Denver.  Northeast winds were sustained to 17 mph.

In 1993…sporadic high winds occurred across metro Denver. Significant wind gusts included 97 mph at Rollinsville… 80 mph in southwest Boulder…and 55 mph at Stapleton International Airport.  The strong winds snapped a pine tree top…about 15 feet long and 8 inches in diameter…which crashed through the roof of a church in Evergreen…causing one thousand dollars in damage.  Wind gusts of 50 to 60 mph caused structural damage to 3 homes under construction in Broomfield.  Northwest winds gusted to 55 mph at Stapleton International Airport.

In 1995…the second spring storm of the month dumped heavy snow in the foothills.  The upslope flow along with areas of thunder snow dropped 6 to 12 inches of snow in the foothills west of Denver and Boulder.  Snowfall totaled 4.6 inches at the site of the former Stapleton International Airport…but most of the snow melted as it fell.  East winds gusted to 29 mph at Denver International Airport on the 18th.

18-20

In 1966…sub-freezing temperatures caused thousands of dollars in damage to fruit trees across metro Denver. Minimum temperatures were in the teens each morning and failed to reach above freezing on the 19th.  The low temperature of 13 on the 20th set a new record minimum for the date.  Snowfall totaled 5.7 inches at Stapleton International Airport during the period.

19

In 1899…northwest winds were sustained to 48 mph with gusts as high as 60 mph in the city.

In 1941…the last snow of the season…0.4 inch…occurred… Marking the end of the shortest snow season…167 days. The first snow of the season…a trace…occurred on November 4…1940.

In 1954…strong gusty winds raked metro Denver for most of the day producing some blowing dust.  At midday…a severe dust devil was sighted in the Westwood area of southwest Denver.

In 1955…cold west winds at 52 mph with gusts as high as 69 mph were recorded at Stapleton Airport where blowing dust reduced the visibility to 1/2 mile.

In 1960…the second wind storm in 3 days produced sustained west winds up to 44 mph with gusts as high as 58 mph at Stapleton Airport.  Winds were strong and gusty most of the day…but no damage was reported.

In 1963…the second windy day in a row produced west- northwest wind gusts to 52 mph at Stapleton Airport.

In 1971…a tornado occurred in the southwest corner of weld County about 10 miles west-northwest of Brighton.  The storm moved through a farm yard damaging equipment and structures.  The strong tornadic winds lifted a stock tank over 2 fences into a corral 150 feet away.  Later…a tornado touched down briefly west-southwest of Buckley Field…8 miles southeast of Stapleton International Airport.  No damage was reported.

In 1985…high winds occurred in the foothills.  Winds gusted to 97 mph atop squaw mountain in the foothills west of Denver.  West winds gusted to 37 mph at Stapleton International Airport.

In 1987…a powerful cold front produced high winds and engulfed metro Denver in huge clouds of blowing dust that lowered the visibility to as little as 100 yards.  The cold front generated winds as high as 72 mph at Brighton…67 mph in Thornton…and 54 mph at Stapleton International Airport. Winds of 50 to 70 mph were common along the Front Range from Denver north.  The high wind gusts flipped a light plane taxiing at Stapleton International Airport…slightly injuring two people on board.  The cold front dropped the temperature from a high of 80 degrees at 3:00 pm to a low of 33 degrees at midnight.  Nearly an inch of snow…0.8 inch… Fell at Stapleton International Airport before midnight.

In 1988…a tornado touched down in Fort Lupton…following a path 50 to 75 yards wide for 2 1/2 blocks.  The twister damaged roofs on 2 schools and broke numerous windows; about 10 houses were damaged and several cars had windows blown out.  Several trees were downed.

In 1989…winds were clocked to 68 mph in Wheat Ridge. Microburst winds gusted to 35 mph at Stapleton International Airport.

In 1996…high winds gusting from 70 to near 100 mph developed in the Front Range foothills and adjacent plains.  Numerous power outages were reported as power lines and poles were downed.  The high winds blew the chimney off the roof of a house in Westminster.  Numerous homes received minor shingle damage.  Some of the stronger wind gusts included:  98 mph at Jefferson County Airport in Broomfield…91 mph atop Squaw Mountain west of Denver…and 75 mph atop Table Mesa near Boulder.  West northwest winds gusted to 45 mph at Denver International Airport.

In 2001…westerly Chinook winds…gusting as high as 40 mph at Denver International Airport…prevented the low temperature from dropping below 51 degrees…setting a new record high minimum for the date.  The high temperature of 77 degrees was not a record.

In 2005…severe thunderstorms produced large hail across metro Denver.  Hail as large as 1 1/4 inches in diameter was measured in Arvada.  Hail to 1 inch in diameter fell in Westminster…Northglenn…and Thornton.  Hail to 7/8 inch was reported near Brighton…Barr Lake…and Castle Rock. Hail to 3/4 inch fell in Elizabeth and Broomfield and near Golden…Brighton…and Fort Lupton.

19-20

In 1892…rain on the 18th changed to snow on the 19th and totaled 6.0 inches over downtown Denver into the 20th. Total precipitation was 1.56 inches.  North winds were sustained to 26 mph on the 19th.

In 1907…a major storm dumped 18.0 inches of snowfall in downtown Denver.  Much of the heavy wet snow melted as it fell.  The most snow on the ground was 7.0 inches at 6:00 pm on the 19th.  North to northeast winds were sustained to 42 mph on the 19th and to 21 mph on the 20th.  High temperatures were in the low to mid 30’s with low readings around 20.

» Click here to read the rest of April 18 to April 24: This week in Denver weather history

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Severe Weather 101 – Severe Weather Awareness Week wrap up

Saturday, April 17th, 2021 5:00am MDT
Supercell thunderstorms like this can be beautiful - but they can also be deadly. Do you know what to do when severe weather strikes? (Stormscape Photography / FLICKR)

Supercell thunderstorms like this can be beautiful – but they can also be deadly. Do you know what to do when severe weather strikes? (Stormscape Photography / FLICKR)

Over the past week we have highlighted some of the severe weather hazards that we face in Colorado every spring and summer in our Severe Weather 101 series.  The dangers these present are significant and not to be taken lightly.

Tornadoes grab most of the headlines and certainly are a danger however others like lightning and flooding are more common and actually claim more lives.  We ask all of our readers to please, take the time to review these important articles – they could save yours and your family’s lives!

The National Weather Service has published a nice wrap up of Severe Weather Awareness Week that covers all the basics – see it below.  For more in depth information, please use the links at the bottom to view each article on our Severe Weather 101 series.  Be safe and be weatherwise!

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
600 AM MDT SAT APR 17 2021

SEVERE WEATHER AWARENESS WEEK IN REVIEW

Severe Weather Awareness Week in review…

Severe Weather Awareness Week in Colorado concludes today. During the past week we have presented information and safety rules for tornadoes, lightning and wildfires, floods and flash floods, straight-line thunderstorm winds, hail, and our warning programs.

We will now review some of the most important safety rules in our effort to build a Weather-Ready Nation.

Be weather-wise by staying informed on expected weather in your area. The National Weather Service is typically aware of the potential for severe weather many hours or even days before any severe weather watches or warnings are issued, providing forecast products to heighten your awareness. A Weather Story product is posted each day on National Weather Service Internet pages and Facebook pages which includes a map and text on possible hazardous weather expected within the next seven days.

A Hazardous Weather Outlook is also issued daily with information on possible hazardous weather through the next seven days. A watch is issued when conditions for severe weather or flooding become possible. A warning is then issued when life threatening conditions are imminent or occurring.

Tornadoes

Tornadoes can even strike in mountain areas. In 2008 on August 23rd, this rope tornado struck Park County near Eleven Mile Reservoir. Image courtesy Jerry Bivens.

Tornadoes can even strike in mountain areas. In 2008 on August 23rd, this rope tornado struck Park County near Eleven Mile Reservoir. Image courtesy Jerry Bivens.

The best way to protect yourself from tornadoes is to have a plan of action. The safest place to be if a tornado approaches is in a basement or safe room within a well-built structure, or in an underground storm shelter. If none of these options are available, move to a hallway or a small interior room on the lowest floor, usually this is a closet or bathroom. Get under a heavy piece of furniture or in a bath tub and cover yourself with blankets. Remember, the greatest risk of injury from tornadoes is from flying debris.

Modular homes and mobile homes, even those tied down, offer little protection from tornadoes. If a tornado approaches, leave those locations and seek safety in a nearby sturdy building or storm shelter.

If you are driving in open country and see a tornado, if time permits, the best thing to do is simply drive away from the tornado path. Do not take shelter beneath a highway overpass. Wind speeds may actually be higher in these areas and often become collection points for debris.

If you are caught outside and cannot seek shelter inside a sturdy structure, crawl into a culvert or lie down in a narrow ditch or ravine and cover your head. But remember that the worst place to be when a tornado threatens is outside in the midst of flying debris.

Lightning

Lightning usually kills and injures more people in Colorado than any other thunderstorm hazard. Lightning also causes many wildfires.

The best defense to protect yourself against a lightning strike is to plan ahead and avoid being caught where you might be vulnerable. Check weather forecasts prior to venturing out, especially if you are heading into the mountains. Plan outdoor activities early in the day before storms develop.

If thunderstorms threaten, seek shelter in a building or in an enclosed metal-roof vehicle, making sure all windows and doors are closed. Never seek shelter under an isolated tree. During thunderstorms, stay off corded telephones, away from electrical devices, and away from plumbing. Also get out of shower stalls, bath tubs, swimming pools and lakes when lightning is nearby.

You should wait at least 30 minutes after the last sound of thunder before resuming outdoor activities. When thunder roars…go indoors.

Floods and Flash Floods

The Big Thompson Flood in 1976 claimed the lives of 144 Coloradoans and serves to remind us of the dangers of floods. (USGS)

The Big Thompson Flood in 1976 claimed the lives of 144 Coloradoans and serves to remind us of the dangers of floods. (USGS)

When flooding or flash flooding is possible, you should remain alert and be ready to quickly evacuate to higher ground or climb to safety. Flash floods often occur suddenly and without warning. You need to follow some basic flood safety rules:

  • Do not camp or park your vehicle along streams and washes, particularly during threatening conditions.
  • If you are near a river, be aware of water levels and be prepared to move to higher ground if river levels rise.
  • Do not enter areas that are already flooded.
  • If walking or fishing along a river, be aware that erosion from swift running water can cause river banks to collapse.
  • Never let your children play around high water, storm drains, viaducts or arroyos.

At least half of all flash flood fatalities are vehicle related. While driving your automobile, look out for flooding at highway dips, bridges and low areas. Two feet of moving water will carry away most vehicles. Never attempt to drive across a flooded road. And be especially cautious at night when it is difficult to see flood dangers.

Strong Straight-Line Winds

Straight-line winds from thunderstorms, including microbursts, can become quite strong, even reaching speeds in excess of 100 mph in extreme cases. When thunderstorms approach, high winds can suddenly develop, causing things on the ground to become swift moving airborne missiles with a potential force to injure or kill. As with any thunderstorm, seek shelter before the storm arrives.

Hail

This is one of the largest recorded hail stones which is more than 7 inches in diameter and fell in Nebraska in 2003. (NOAA)

This is one of the largest recorded hail stones which is more than 7 inches in diameter and fell in Nebraska in 2003. (NOAA)

Large hail can pose a danger to animals and people. Hail also produces considerable damage to crops and personal property each year in Colorado. Again, get indoors before thunderstorms arrive. A fall of small hail can suddenly change to a fall of very large ice missiles which can injure or kill. Make efforts to protect personal property before storms threaten.

Warning Notification

When thunderstorms threaten, tune to NOAA All-Hazards Weather Radio, The Weather Channel, or your local radio or television stations. Also check the Internet web site from the National Weather Service office serving your area. And if you have a relatively new cell phone you should receive Tornado and Flash Flood Warnings on your phone if you are in the area of the warning.

During threatening weather days, plan the actions you will need to take so that you will be prepared if dangerous weather conditions actually develop.

NOAA’s National Weather Service wishes you a safe severe weather season.

Severe Weather Awareness Week in Colorado concludes today. During the past week we have presented information and safety rules for tornadoes, lightning and wildfires, floods and flash floods, straight-line thunderstorm winds, hail, and our warning programs.

 

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Thornton’s weekend starts out cold with some snow, ends warm and clear

Friday, April 16th, 2021 5:01am MDT

A little bit of a mixed bag of weather for us over the three day period. Today and tomorrow we will be shaking off our most recent storm but Sunday looks to be nice.

As of 4:00am Thornton had received 5.8 inches of snow. Some additional, light accumulations will be possible today, mainly before noon. After that, more flakes may fall but little / no accumulation is expected. Highs today will top out only in the mid-30s. Tonight, it will be mostly cloudy with a few flurries possible. Overnight lows will be in the mid-20s.

Saturday will see some improvement but still not be all that great. Highs will be in the mid-40s. It will be mostly cloudy initially but then gradual clearing will follow in the afternoon. Some light flurries with no accumulation will be possible. Saturday night, skies will begin to clear and overnight lows drop to the mid-20s.

Sunday will be the nicest day of the period. Look for sunny skies above with calm, dry conditions. Highs will be in the mid-50s.

Have a great weekend!

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Severe Weather 101 – Lightning and lightning safety

Friday, April 16th, 2021 3:08am MDT
This is NOT the time to be outside. (michaeljames / FLICKR)

This is NOT the time to be outside. (michaeljames / FLICKR)

Of all the weather types associated with thunderstorms – hail, tornadoes, floods, etc – lightning is usually the most dangerous. In the United States there are an estimated 25 million cloud to ground lightning flashes each year and each one is a potential threat to life and property.

During the past 10 years there has been an annual average of 39 lightning fatalities in the United States. Last year, 23 people lost their lives due to lightning.

Colorado is ranked # 2 in lightning related deaths (2001 – 2010) so the danger this presents to life and property is very significant for us. It is interesting to note though that Colorado ranks only 32nd in the number of cloud to ground strikes over that same period. Which means, in short, we have fewer strikes than many other states and yet more deaths.

This highlights the fact that, quite frankly, folks here in Colorado are not aware of the dangers lightning presents and they do not take proper steps to protect themselves. One of the great things about Colorado are the outdoor activities we all enjoy, but there comes a time when we need to head indoors.

» Click here to read the rest of Severe Weather 101 – Lightning and lightning safety

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Thursday to finally bring some moisture, initially rain, then turning to snow

Thursday, April 15th, 2021 5:17am MDT

We’ve had a couple of false alarms this week, expecting showers the last couple of evenings that never materialized. Today is certain to be different with rain to be followed by snow.

Cloudy skies start us off and will be with us throughout the day. There isn’t really anything to indicate we will get a break in the coverage. High temperatures today will top out in the mid-40s around 1:00pm then begin cooling off early. Winds will be light this morning, becoming breezy in the afternoon and overnight hours.

Early afternoon will see some sprinkles of rain with coverage increasing by about 3:00pm, becoming widespread around 5:00pm. The change to snow, right now, looks to occur around 6:00pm and then light snow will be relatively constant into tomorrow morning. This isn’t going to be a big snowmaker but Thornton can expect 2 to 4 inches overnight.

Low temperatures tonight will drop to the mid-20s.

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Severe Weather 101 – Hail and Wind

Thursday, April 15th, 2021 3:06am MDT
Straight line winds can be as damaging as a tornado. This image is from a park in Tennessee. (NWS)

Straight line winds can be as damaging as a tornado. This image is from a park in Tennessee. (NWS)

During the spring and summer months in Colorado, a wide array of severe weather can strike. Tornadoes may grab all the headlines, but straight line winds and hail can do a great amount of damage in their own right – and they are more common.

Straight line winds are winds out of a thunderstorm and are classified as severe when they hit 58 mph. These winds can reach tornado and hurricane force and as a result, cause property damage and can injure and even kill animals and humans.

These winds are usually the result of air cooling rapidly due to precipitation or evaporation. As the cooler air is heavier than the surrounding warmer air, it rushes downward, accelerating toward the ground and spreads out as it hits, much like pancake batter being poured onto a griddle.

» Click here to read the rest of Severe Weather 101 – Hail and Wind

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Cool temperatures, a good bit of cloud cover Wednesday

Wednesday, April 14th, 2021 5:20am MDT

Another kind of “blah” day for Thornton. Daytime hours should stay dry but it will be cool and cloud cover pretty consistent.

Cloudy to mostly cloudy skies start us off then coverage will ease a bit up until early afternoon when it will again build. High temperatures today will top out in the mid to upper 40s.

At this time it looks like we will stay dry until the evening when we could see some light sprinkles of rain. As it gets colder, some snow but with little to know accumulation will be possible overnight. Lows tonight will dip to the low to mid-30s.

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Severe Weather 101 – Floods and Flash Floods

Wednesday, April 14th, 2021 5:05am MDT
The Big Thompson Flood in 1976 claimed the lives of 144 Coloradoans and serves to remind us of the dangers of floods.

The Big Thompson Flood in 1976 claimed the lives of 144 Coloradoans and serves to remind us of the dangers of floods.

For much of Colorado, floods and flash floods present a grave danger to life and property. These usually are the result of one of two things – spring snow melt occurring rapidly or a severe thunderstorm. Colorado is very susceptible to flash flooding and these occur somewhere every year in the state.

The waters from flash floods can move with extraordinary speed and strike with little or not warning.  Their force can be extremely destructive and when coupled with trees, dirt, rocks and other debris they carry downstream, they are deadly.

Flooding is the number one weather killer in the United States.

» Click here to read the rest of Severe Weather 101 – Floods and Flash Floods

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