Final Forecast- Timing, Snow Totals, and Temperatures for the December 6th Snow Storm

I’ve been keeping a close eye on this storm for quite a while leading up to today. The promise of snow and possibility of below zero temperatures after a summer that was seemingly endless filled me with endless amounts of excitement. Then again, I’m a winter person and I love cold weather, your feelings about this storm system may vary. Regardless of whether you’re excited about the cold and snowy weather, it has arrived and will make things treacherous over the next 24 hours!

Today’s forecast will be broken into the following sections-

  1. Current Conditions
  2. Storm System Timing
  3. Expected low temperatures (possibly record-breaking)
  4. Expected Snow Totals
  5. Summary

Current Conditions

visible

Visible satellite image 9:15 MST December 6th, 2016

The front range has clear skies and that has contributed to low temperatures in the low teens and even around 10°F over night.In fact, most areas are still hovering right around the 10°F mark currently, but negative temperatures lie just to our north in Wyoming and they will make their way down here by tomorrow tonight. Cloud cover is positioned over the western part of the state and, as this storm system makes its way from west to east, the front range will eventually become cloudy later this morning and afternoon as well.

Storm System Timing

Obviously this system has already started to come through the state with our big drop in temperatures over the last 24 hours and high winds last night (that reached 75mph at the NCAR Mesa Lab!). The snow associated with this storm system should start making its way  into the metro area late-afternoon around 5-6pm and will continue through most of the day tomorrow. Initially, snowfall rates will be light but should start picking up intensity around rush hour this evening. The heaviest snowfall rates should occur late tonight between 9pm and midnight while light snow and flurries will continue through much of tomorrow.

Expected low temperatures (possibly record-breaking)

screen-shot-2016-12-06-at-9-20-04-am

Forecast Temperatures at 5am MST December 08, 2016

The real story with this storm won’t be the snow totals, but the dangerously low temperatures that we’ll encounter tomorrow night (and tonight to a lesser degree). Lows around the Denver metro area are expected to dip down below zero and will be between -5°F and -10°F for most areas with wind chills that could be between -15°F and -20°F on Wednesday night. Tonight, we’ll still be cold with temperatures in the single digits and wind chills possibly below zero, but the clouds will help keep some heat near the ground whereas tomorrow night, they will not. These are dangerous temperatures and should not be taken lightly. Make sure to keep your pets inside and dress warm and in layers if you have to go outside. Also, make sure that you have an emergency kit in your car that includes a blanket. It will only take 30 minutes to incur frostbite on exposed skin in these temperatures!

Expected Snow Totals

screen-shot-2016-12-06-at-9-36-40-am

Global Forecast System (GFS) 12Z run Snowfall Totals through 8pm MST December 7th, 2016

I’m expecting 2-5″ for most areas around the front range with slightly higher amounts of 3-6″ along the foothills and more as you venture into the mountains. Bear in mind that this is 2-5″ of snow by Wednesday night. This has been a particularly challenging forecast because of the cold temperatures that will be associated with the snowfall.

Cold temperatures mean that we can get more snowfall accumulation from similar amounts of water. As an example, think of the champagne powder that falls in the mountains. It’s light, fluffy, and very “dry” snow which allows it to move easily and create those brilliant powder clouds that shoot over your head when skiing or snowboarding. By comparison, think about spring storm snowfall. It’s wet, heavy, and incredibly difficult to shovel when it accumulates on your sidewalk.

It all comes down to what is known as the snow to liquid ratio (SLR), which gives a certain amount of snow accumulation per inch of liquid water in the atmosphere. Generally we use a 10:1 ratio which means that we get 10″ of snow to 1″ of water that falls. However, spring storms can be as low as 6:1 or 8:1 and very cold winter storms can be as high as 20:1 or 30:1. For this storm, I’m expecting a SLR of approximately 20:1 due to the low temperatures. This means that we’ll see light and fluffy snow out of this storm and it won’t have a ton of moisture (easy shoveling!). Colorado needs all the precipitation that it can get!

Summary

Snow will arrive in town early this afternoon and will continue through Wednesday afternoon. While 3-6″ of snow are expected in most areas, the real hazard will be the dangerously low temperatures in single digits tonight and below zero tomorrow night. Snowfall rates will be most intense over night tonight, but light snowfall will continue through tomorrow and will make commutes slippery and dangerous. Again, make sure that you have an emergency kit in your car and stay warm, friends!

Thanks for reading! Feel free to comment or ask any questions!

-Andrew

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