Brief Outlook- Bitter Cold and Snow for Denver


Temperature at the National Center for Research Winter Weather Test Site in Marshall, Colorado (Just south of Boulder)- December 05, 2016

Edit: Ignore the (C) on the y-axis of the plot. It’s actually in Fahrenheit but the axis title didn’t chance.

Denver and the surrounding regions have already started to cool off dramatically after the passage of a cold front earlier that has caused temperatures to drop ~14°F in the last few hours. We’re still about 10°F warmer than tomorrow’s expected high temperature of 28°F which means that we still have a lot of cooling off to do tonight. In fact, we’re going to be dropping into the low teens this evening. A Winter Weather Advisory has been issued by the National Weather Service and can be found below.

Winter Weather Advisory-








As we edge closer to the storm system that will impact us tomorrow and Wednesday, some things are clear and others are still a bit fuzzy. What we know is that we will see a pretty drastic change to our weather that has been relatively mild over the last few days and we’ll wind up with frigid temperatures and snow arriving in Denver tomorrow afternoon and continuing through Wednesday. However, we still don’t know just how much snow we’ll actually be getting. There is a bit of disagreement between models, but the overall consensus is that it’s looking like 2-4″ of snow for most areas around Denver that will fall primarily between late afternoon/evening tomorrow through Wednesday morning. Snowfall will be relatively light, but heavier areas in the foothills, mountains, and to the east of Denver are expected.

A more comprehensive forecast will be available tomorrow morning so make sure to check back!

Thanks for reading!


Denver Parade of Lights 2016 Forecast


A joyful family enjoys their local Christmas Parade in Hohman, IL. Through an unprecedented  string of good luck earlier in the month, the father had received a “major award” and their son was recruited to help with the rigorous decryption of important messages. (1940, colorized)

Tonight’s the night! The 2016 Denver Parade of Lights will march past the Denver City and County Building and through the streets of Downtown Denver. First-nighters, packed earmuff-to-earmuff, will jostle in wonderment before a golden, tinkling display of mechanized, electronic joy!

Floats, marching bands, and all sorts of wild acts will fill the streets of Denver to the delight of children and adults-who’ve-had-too-much-hot-chocolate-and-Peppermint-Schnapps alike! However, what will the weather be and what will I need to wear if my Schnapps doesn’t keep me warm enough?! Don’t worry! I’ve got you covered.

Parade Tonight

Tonight’s parade and festivities will definitely be cold as will tomorrow night as well. We’ll be sitting around 26°F when the parade kicks off at 8pm and by the time it ends at its last point around 9 or 10pm, we’ll be around 21°F with wind chills as low as 17°F. Now, bear in mind that these are wind chills for all of Denver and that the winds are really amplified by the tall buildings downtown which means that the temperatures could feel another 5° colder. Some light snow is also possible late this afternoon and early this evening which means road surfaces could be wet or icy. Make  sure that you plan ahead and give yourself extra time, if needed.

Parade Tomorrow

With an earlier start and a sunny day ahead of it, temperatures at the kickoff of the parade tomorrow should be about 10° warmer than they will be tonight at 36°F and a balmy (in comparison) 30°F at the end of the parade. With that being said, there is a higher chance of wind chills tomorrow that could make the forecasted temperatures feel about 5° colder than reality. Tomorrow’s ramp up to the parade promises to be drier as well with sunny skies to get rid of any moisture left on the concrete and asphalt surfaces. It should make for easier watching with the ability to sit on the sidewalk for the kiddies.


A young boy fulfills his dream of speaking with Santa about his love of football only to realize, after the conversation, that his real desire is weaponry.


Overall, it will be cold for either parade and they both will require bundling up and hand warmers. However, the parade at 6pm tomorrow looks to be a little warmer and, more importantly, drier. We all know how hard it is to stay warm if you’re wet and it will be downright impossible if you’re wet and temperatures are in the 20s and 30s. So, if warmer weather is a factor for your voyage to the parade, tomorrow might be the best route. If you’re like me and enjoy pretending that you’re lost in a arctic wasteland and the only salvation is the soft glow of electric sex gleaming in the… ok, that Christmas Story quote doesn’t work here. Let’s try that again. If you’re like me and enjoy pretending that you’re lost in a arctic wasteland and the only salvation is the soft glow of electric lights and the anxious anticipation of seeing Santa in his sleigh, Friday might be right up your alley.

Thanks for reading! As always, feel free to ask questions and I’ll answer as quickly as possible.


First Snowfall Forecast

The day of infinite glory is upon us! Our first snowfall of the 2016/2017 winter is falling in a few places along the front range. The mountains will be getting their fair share of the white fluffy stuff as well as they get some much neededermahgerd relief from the incredibly dry and record-breaking hot weather of the last month.

Assuming that the forecast isn’t completely wrong, we will have our first measurable snowfall of the season just four days before we would have broken the record for the latest first snowfall in Denver history. While this storm isn’t going to dump feet of snow or have you on the couch for days drinking hot cocoa and watching Netflix (it might, who am I to tell you what to do with your life), it is going to give us much needed moisture. For many of us though, this storm is not about the moisture in an increasingly dry year, it gives us  some peace of mind that winter has not forgotten us. It’s a simple reminder that we are, indeed, marching forward towards the holidays, skiing and riding the mountains, winter breaks from school, and that we’re not just stuck eternally in an endless late summer. How sweet it is!

Anyway, this is going to look like a fairly normal forecast and will be broken down into these categories-

  1. Current Conditions
  2. Storm System Timing
  3. Expected Accumulations
  4. Summary (If you don’t want the specifics, skip to this one!)


Current Conditions

Yesterday afternoon we experienced a cold front coming through the area that has kept our temperatures falling for about 12 hours now. Current temperatures are in the mid-30s around the front range and humidity has increased steadily. Yesterday’s cold front brought plenty of cloud cover as we can currently see blanketing the metro area in a wonderful sheet of grey this morning. Snow and rain have just barely started making their way onto the front range and can be seen on the radar image below. Right now we can see plenty of snowfall in the mountains and, although there is some green in areas like Longmont, Westminster, and to the west of Boulder, that is most likely radar noise and not actually rainfall.


Radar Image: 10:00am MST Nov 11, 2016 — Blue signifies snow and green signifies rain, darker colors means heavier snow/rain.

Storm System Timing

The latest model runs show rain and snowfall beginning around town at approximately 11am MST. Initial thoughts were that we were going to get a period of rain followed by a longer period of snowfall that would last until roughly midnight. However, with the cooler temperatures around the metro area, it’s looking like the switch from rain to snowfall should happen sooner rather than later and there’s a good possibility that light snow will be falling in time for the evening rush hour commute. The snow still looks to finish off right around midnight and cloud cover should be clearing out shortly thereafter. I’m so happy to be able to say this… be prepared for very cold temperatures tonight. Most of the front range will be down into the teens and low twenties. Don’t be caught unprepared!

Expected Accumulations

Right now we’re right on par with what we’ve been expecting over the last few days, 1-2″ for the Denver area, 2-4″ for areas south and west along the foothills, and 3-6″ at most mountain locations along the I-70 corridor. There is a possibility for some higher amounts on the high mountain peaks like Echo Mountain, Breckenridge, and Vail, but it isn’t going to effect much down here. Keep in mind that despite the snowfall accumulation predictions, we might not actually see that much laying on the ground because the ground temperature is exceedingly warm from our record breaking temperatures. You will still probably see some accumulation on patio furniture and things of that nature (Don’t tell Kyle Clark), but it won’t be on everything.

You might notice that on the snowfall map there is a lot more snow out east, this is not a glitch. The northeastern plains of Colorado are expecting more snow than the Denver metro area. Make sure that you are prepared for poor driving conditions if you are headed out that way!


Expected snowfall amounts from this storm


This storm has already brought us cooler temperatures and they will continue to stay low today and will be downright frightful tonight with lows in the teens and low 20s.  Snowfall beginning soon will bring 1-2″ for most areas and 3-4″ for a lucky few. Other than wet roads, there shouldn’t be much impact from this storm system today. However, tomorrow 3bbf5610b9b464b562e30cfddc491f39morning could yield a few icy conditions after roads have cooled a bit and remained wet overnight. My best advice for this storm is to enjoy it. We’re a week away from Thanksgiving and are FINALLY getting cold weather!

In my opinion, there has been a lot to make just about anyone anxious lately and the holidays are coming up which can make people even more anxious. That’s why I can’t stress this enough. Even if you don’t like winter, take a page out of Linus’ book and go catch snowflakes on your tongue! It keeps you hydrated and is a great way to remind yourself that life isn’t all about nonsensical bickering!


Thanks for reading! I hope you enjoyed the forecast.


Five Day Forecast Sept 26th, 2016


Beaver Run in Breckenridge Sept 25th, 2017     Photo Credit: Megan Schwartz

Another new product today! I’ll be doing brief weekly weather write-ups on Sundays and/or Mondays for those that wanted something to be posted on a more regular basis. These will be known as “Five Day Forecasts” and will actually include an outlook for the foreseeable future past five days as well. Let me know if there’s anything that you’d like to see in them and I’ll do my best to accommodate your request!

It’s definitely cold outside this morning as temperatures hover in the 40s for most of the state and fresh snow that fell over the weekend blankets the highest mountain peaks. We are certainly living up to the Autumn season after the first official day of meteorological Fall occurred last Thursday the 22nd. A brief respite from cooler temperatures will come again this week, but will transition into cooler temperatures this weekend and early next week. However, our temperatures continue to be above the daily averages this year and we won’t see any big cool downs in the foreseeable future.

Next Five Days

Today- Abundant sun will help us see highs in the mid-70s around town today before cooling down to the mid-40s tonight under clear skies.

Tomorrow (Tuesday)- After a day of recovery from cool temperatures on Monday, highs for the Denver Metro area will be in the upper 70s and low 80s with a few stray clouds. Low temperatures at night will reflect the slight warming trend and will be in the low 50s.

Wednesday- Very similar to Tuesday with highs in the upper 70s and low 80s, mostly clear skies, and lows around 50 degrees.

Thursday- A few more clouds will build into the region as our next small weather system begins to arrive in Colorado. Highs will again be in the upper 70s and low 80s and our overnight lows will be in the mid-50s.

Friday- A low pressure system entering the state will make its way to the eastern plains and will bring a small chance of rain and thunderstorms with it. We’ll see an increase in clouds over Thursday and will have highs that are a few degrees cooler in the mid to upper 70s.


Extended Forecast

This upcoming weekend we’ll see another cool down similar to the one that we had this past Saturday and Sunday, but with one notable difference. Based off of the current model runs, the next storm system that comes into the state on Thursday will intensify on the eastern plains until it continues on its path on Monday. However, there is indication of a second storm system that will immediately follow the first one! Between these two systems, we could be looking at a few light rainy days from Saturday through Tuesday of next week. One thing is certain, we are beginning to see weather patterns that are indicative of active fall and winter weather rather than the ones that produce our boring summer weather!


As always, let me know how I can improve these posts and if you’d like me to cover anything specific.

Thanks for reading!


Denver’s Autumn and Winter Outlook

It’s no secret that the hot and sweaty dog days of summer are over. There’s fresh snow on the mountain tops, grey skies, and even a few changing leaves around town. Over the last few days we’ve noticed a big dip in temperatures around the Rocky Mountain region and we’re beginning to enter a period with seasonally average temperatures, which is a nice departure from what has become the hottest year on record across the globe. However, we seem to have returned to 90° temperatures after having similar cool downs in the last two months. So, there are some real questions


I70 Eastbound Near Frisco on September 16th, 2016

as far as weather cooler temperatures will continue and, realistically, what Fall and Winter will have in store for us.

Let’s dive into these questions, but first, we’ll examine how seasonal forecasts are made, their strengths and shortcomings. As always, I’m going to break this into sections. If you want to skip the science-y stuff and go right to the forecast! No problem, just skip ahead.


  1. Climate and Weather Models
  2. The Farmer’s Almanac
  3. El Nino/La Nina Impacts on Colorado Weather
  4. Fall and Winter Forecasts


Before we continue, something important to note is that climate and weather are NOT the same thing. Weather is short term, smaller in scale and much more erratic. Climate is long term, larger in scale (think all of Earth) and follows trends.

Climate and Weather Models

Trade offs, trade offs, trade offs! It’s no secret that we are not very good at predicting the weather far in advance, but few people actually know why it’s so difficult. It’s comes down to trade offs between length of prediction (how far into the future we’re forecasting) and the size of the area we’re trying to predict. Why? Why does this trade off exist? We’re going to start with something that I saw from my professor, Dr. Sam Ng, multiple times when I was in school. Get out the bongos and get ready to snap your fingers because it’s a poem! Yes, that’s right, a poem by Lewis Fry Richardson who actually changed it from someone else’s poem, but that doesn’t matter.


WRF Model of Hurricane Sandy

“Big whirls have little whirls,
That feed on their velocity;
And little whirls have lesser whirls,
And so on to viscosity.”

Ok, I know what you’re thinking, “This poem sucks”, and you’re not wrong, it does. However, it perfectly describes our current issue with weather and climate modeling. When we talk about the atmosphere we see interactions everywhere. We see the transport of temperature, moisture, soil, gases, mass, aerosols, etc. These motions don’t exist only at large planetary scales, they shrink down to be infinitely small. They also exist in three dimensions that can interact with each other! That’s a “duh!” statement, but we have to make sure that we’re on the same page. Each parameter of the environment has its own unique set of governing equations in addition to the overall equations that describe the motion and evolution of the atmosphere and current computational power isn’t enough to get long range forecasts on small scales that can predict snowfall on a neighborhood by neighborhood basis. Hence, why there are so many botched forecasts.

For example, the NCAR supercomputers that we use to run the Weather Research and Forecasting (WRF pronounced warff) model can compute 5.34 quadrillion calculations per second and yet, they are still extremely limited in their processing abilities for detailed models.

It all comes down to grid spacing within the model structure. Our most detailed operational model, the High Resolution Rapid Refresh (HRRR), operates at 3km grid spacing and forecasts out to 24 hours in the future. It is generally assumed that, in order to resolve a weather feature, three grid points are needed. This means that our most detailed model can only resolve features that are bigger than approximately 5.5 miles. Now 5.5 miles sounds small,  but it could mean the difference between the model predicting that downtown Denver will get hit and then only the areas west of Wadsworth seeing snow and Denver not getting any. Sound familiar from last year when the foothills and southern areas got snow and Denver saw almost nothing?


HRRR Model Forecast Vs. Observed Storm System- Good but not perfect

Due to its high resolution, the HRRR can only realistically be run for short forecasts in the future before it becomes computationally expensive/problematic. It is very reliable for short term forecasts and detail in small areas, but it comes at the cost of only being short term. By comparison, our climate models do very well with long range forecasting, but at the price of detail. We can accurately predict future climate patterns, but we won’t be able to have the fine details of individual weather systems and rainfall/snowfall. So, there’s that trade-off mentioned earlier. We can either use all our processing power on looking far into the future or we have to focus it on looking at very small areas. We can’t do both.


Now, this is assuming that all the data that we have pumped into these models is absolutely perfect and, you know what? It’s just not. We do a fairly good job of making measurements of the atmosphere and feeding it into the models, but the instrumentation sites are sparse and have limitations and that can create problems. Imagine an errant temperature measurement propagating forward in space and time every five minutes for thirty days! SCARY! Overall, our long range (climate) models and very short range (weather) models perform well. It’s those intermediate models that tend to have issues. So, when we are asked what the future holds and what the models are saying about seasonal weather in a particular region, it’s not as straight forward as it sounds.

The Farmer’s Almanac

For some reason, people LOVE the forecasts presented by the Farmer’s Almanac. I’m not entirely sure whether it’s due to nostalgia, good marketing, or maybe people just like to say “almanac”. It is kind of fun to say. Sounds a bit like a french pastry. “I’ll have two croissants and a raspberry almanac!” Anyway, the Farmer’s Almanac really isn’t any more reliable that any other forecast out there (maybe AccuWeather’s 90 day forecast) and its approach to forecasting weather is fairly common sense. They don’t havefarmers-almanac_0 a gypsy fortune teller tied to a weather tower or anything.

According to their webpage-

“We derive our weather forecasts from a secret formula that was devised by the founder of this Almanac, Robert B. Thomas, in 1792. Thomas believed that weather on Earth was influenced by sunspots, which are magnetic storms on the surface of the Sun.”

Apart from the rest of their “secret formula”, which I’m fairly sure is just a fancy way of saying “climatology”, sunspots can be an indicator of weather patterns. EVERYTHING in our atmosphere is driven by solar radiation. Without it, we’re not evaporating water for clouds, temperatures would remain constant and fronts wouldn’t exist (neither would high and low pressure centers), nothing would be happening. So, when a sunspot appears and releases increased amounts of solar radiation, chances are high that we’re going to see additional warming. This is a gross oversimplification of the processes involved, but it conveys the point.

Now, there’s another possible explanation for the love of The Farmer’s Almanac and that’s what’s known as confirmation bias. Many people swear that it’s the only accurate source for weather and, after hearing that enough, others start to believe it and will look for ways (intentionally and unintentionally) to show that it is right. So, when it nails a forecast, everyone praises the Farmer’s Almanac like they did with the “Polar Vortex” outbreaks. However, when Boston had its record breaking snowfall in the 2014/2015 winter, the Almanac had failed to predict it and no one paid attention to it. A prime example of confirmation bias where you only search for data that supports what you already believe. Realistically, it is a good source of rough estimates, but it’s no better than any other source at predicting weather.

As a side note, the Polar Vortex really doesn’t travel into America. Al Roker is an idiot. The Polar Vortex is named for the region that it circles which is…. the north pole. What Al Roker was referring to was an Arctic Cold Front which brings very cold arctic air southward.

El Nino/La Nina Impacts on Colorado Weather


Higher than normal sea-surface temperatures (yellow and red) west of South America during the 1997 El Nino

This is something that needs to be touched on from time to time to remind, even myself, to be aware that there are problems with attributing Denver’s weather to ENSO (El Nino Southern Oscillation). Briefly, increased sea surface temperatures that extend westward for northern South America are classified as El Nino years. Conversely, La Nina years are times with cooler sea surface temperatures. Most often we hear people attribute big snow storms to one or the other.

“This 34 inch blizzard is awesome! I knew El Nino would come through!”

However, looking at the impacts of El Nino or La Nina on a single weather event in Denver isn’t realistic. In fact, there is almost a perfect 50/50 split of Denver’s largest blizzards between El Nino and La Nina years. That’s not to say that it doesn’t effect the weather. It effects weather patterns in a big way and can bring differences in temperature and moisture to different areas, but as far as Denver is concerned, there has never really been a correlation drawn between the ENSO cycle and our weather. This means that all those “We’re transitioning into a La Nina year so we can expect _______!” statements simply aren’t true.

Fall and Winter Forecasts

Over the last week, we’ve seen an extended period of 60 and 70 degree temperatures around the Denver metro area. While a resurgence of mid-80s temperatures will occur this weekend and into the beginning of next week, it looks like our 90 degree days are behind us as we will again see 70s late next week. The current models are showing a typical cool down over the next few weeks and seasonal high temperatures, but they’re also showing almost no precipitation at all. Unfortunately, that looks like a trend that will continue all winter.


Probabilities of higher or lower temperatures from October to December. Orange and reds are above average, blues are below average temperatures.


Probabilites of increased or decreased precipitation. Greens are above average, yellows are below average.

Right now, Denver is looking at a warmer than average winter according to the latest model runs and, unfortunately, that includes the Rocky Mountains as well. The figures above show increased temperature across most of the USA and an equal chance (EC) for above or below normal precipitation. One area of concern is that even if we get plenty of snowfall in the mountains, the warmer temperatures will ensure that it melts off faster and that our water supply is lower come summer. If the current observable trends are any indication, we could be entering into another drought stage later this winter and spring but only time will tell. So, from a climate/seasonal perspective, more of the same. Record breaking heat and drought over much of the United States.

As far as Denver is concerned, it looks like we’ll be warmer than average through all of winter based off of the latest models and information. How much snow or rain we’ll get has yet to be seen, but a wet winter isn’t looking particularly promising.

As always, if you have any questions, feel free to ask here or on Facebook and I’ll get back to you!

Thanks for reading!


Severe Storms for Denver Today with Large Hail and Possibly a Weak Tornado or Two



We’re in the heart of Colorado severe weather season and leading up to this point, we’ve been relatively quiet. The occasional severe storm with hail or strong wind has swiped across the metro area before heading out east, but our severe weather seems to be a lot quieter than at this same time last year. Today, however, that looks to change. Denver and the surrounding areas have an Enhanced risk of thunderstorms today as put out by the Storm Prediction Center. This is something that generally only happens once or twice per year in Denver and is generally a good indication that we are in for some intense weather.



Timing and Risks


A line of storms has already developed to the south and west of Denver along the foothills and looks to be growing to the north. We’re going to start seeing storms develop around Denver and they’ll really pick up in intensity around noon.

Currently, it’s looking like the most significant storms will come through the area around noon and will be followed by a secondary push around 4pm after which storms will continue through tonight. The area at highest risk for damage from the storms is southeastern of Denver in areas like Highlands Ranch, Parker, Centennial, and extreme southeastern Aurora.

The atmosphere has plenty of moisture at the mid to upper levels which means that our most significant threat will be large hail. The latest models show that we lack a lot of the lower level shear (rotation from wind) to support intense tornadoes, however, we will have a southeasterly component to our wind which means that the Denver Convergence Vorticity Zone (DCVZ), which is an area where winds of opposing directions create rotation, will exist to the east of Denver. This area that extends northward along the I-25 corridor from Castle Rock to Denver and eastward from Denver to Limon is notorious for spawning weak landspout tornadoes and should be watched closely this afternoon. With that said, hail will be the primary threat followed by possibly strong and damaging winds. The NWS has not issued a tornado watch at this time. Tornadoes should be limited and, based off of current models, will be weak if they develop at all.

Severe Thunderstorms Today for Denver and Parts of Northeastern Colorado



Tornado near Cheyenne Wells, Colorado May 9th, 2015

Well, we’ve arrived in severe weather season and, while it has been roaring in the central high plains for a while, it’s starting to pick up in Colorado now. We’ve already seen a few tornadoes in extreme eastern Colorado and now it looks like the hail, wind, and tornado threats are starting to move to the west and will be in the front range before too long. While June is typically the busiest month for severe thunderstorms and tornadoes in Colorado, May has its fair share of wild weather events and serves as an introduction for the season.

Today we’ll start our severe weather season for the Denver metro area with a small chance of some hail and high winds although any significant hail and any tornadoes should stay to the east of town along I-76. High moisture in the region will feed storms that currently look like they’ll start on the eastern side of the metro area. On days when we see southeasterly winds (from the southeast), a feature called the “Denver Cyclone” tends to develop which is a broad circulation of air caused by our unique terrain that spins counter-clockwise. The Denver Cyclone aids in the development of thunderstorms and can develop areas of colliding air that produces tornadoes around Aurora, Parker, and Elizabeth. Today, however, any tornado threat should be along I-76.

Understanding Thunderstorm Threats

Below is the Storm Prediction Center’s storm outlook for today. The different categorical outlooks are familiar for those that have lived in places like Texas, Oklahoma, and Kansas. However, those of us that have lived in Colorado or in other locations may not be as familiar with the classification system. The Denver area and the northeastern Colorado plains is under a slight risk area which means that there could be hail between 1-2″, damaging winds, and one to two tornadoes. The I-76 corridor is under an enhanced risk for severe storms which means that severe storms will be fairly widespread, damaging hail and wind reports will be common, and a few tornadoes are possible. A graphic describing severe thunderstorm threats has been added below. The threat category colors correspond to the colors on the map.

Screen Shot 2016-05-24 at 9.46.11 AM

SPC’s Severe Weather Outlook for May 24, 2016



Storms will develop to the east and north of the Denver area early this afternoon between 1-2 pm local time. These storms will intensify and will follow the I-76 corridor to the northeast and will eventually turn into a line of storms that exits the state into Nebraska and Kansas. A primary storm will have the possibility to produce large hail, strong damaging winds, and a few tornadoes. Towns in the immediate impact area include Akron, Brighton, Brush Lochbuie, Fort Morgan, Holyoke, Sterling, Wiggins, Wray, Yuma.

Updates will be made during the day as storms occur. Ask any questions that you have.