Andy's Weather

Long-Duration Snow Event Heading To Colorado

12/13/19 UPDATEHeavy snow is hitting the mountains and has been for about 12-18 hours now. Upwards of a foot has already fallen on some areas like Copper, Loveland and Winter Park Ski Areas. Those areas are bracing for another 1-2′ of snow before things wind down on Monday morning. There’s a lot to update here…

Andy Stein
7 minutes

12/13/19 UPDATE
Heavy snow is hitting the mountains and has been for about 12-18 hours now. Upwards of a foot has already fallen on some areas like Copper, Loveland and Winter Park Ski Areas. Those areas are bracing for another 1-2′ of snow before things wind down on Monday morning.

There’s a lot to update here so scroll to what you find interesting – first, Avalanche Danger then mountain snow update then Denver snow update .

AVALANCHE DANGER:

Avalanche Watches and Warning Up for much of the North Central mountains. 

Avalanches, according to the CAIC, will be easy to trigger by humans. This is a very big concern as more snow is likely to accumulate and avalanche dangers will be ever-increasing. Even small avalanches can harm or kill someone so please take this seriously this weekend. 

SNOW TO COME FOR THE MOUNTAINS

First, where the snow has already fallen.
Snowfall through Friday morning
So far the snow has fallen mainly in the central and northern mountains. Where you see yellow and orange, that’s where 6″+ of snow has already fallen. There have been numerous reports of a foot of snow already falling up there! This is going to be a great ski weekend but not a great travel weekend at all. Travel will be near to impossible at times. Please plan an alternate route or be sure to take your time and have appropriate snow gear and car snow gear handy.  
The mountains are benefiting from what is called an atmospheric river. Basically, a plume of moisture originating from Hawaii is pumping in a lot of Pacific moisture into the state. We don’t typically see atmospheric rivers produce THIS much moisture for Colorado. It’s not unprecedented but it’s abnormal for sure. With that said, there will be a lot more snow to come and a lot of wind that will accompany that. 
ECMWF Snowfall through Monday 
Additional snow to come with be upwards of 12-18″ for a lot of mountain folks – especially above 9,000′.  There will be reports of storm totals of over 3 feet, but where that occurs depends on where the heaviest snow bands set up. Either way, traffic will be miserable, snow will be heavy, wind will be extremely strong and this will last for the next 3 days. 
Winds will be peaking at about 90 mph at the highest elevations but more commonly, 40-80 mph winds will be felt. Those winds will even make it down into Denver. 
DENVER SNOW
Denver hasn’t seen much snow since our big Thanksgiving snowstorm. And there are still piles of snow to confirm that. The snow that is coming for Denver is going to be fickle. The storm track and storm intensity for the snow this weekend has not been consistent. So, what I do know is that most of the models have been suggesting that this storm will be bigger for those South of Denver. Monument, Colorado Springs, Pueblo – you guys will likely see more snow than Denver but if the track of this system starts to meander a little bit more north, we could see more snow in Denver. 
Denver Snow Possibility. 
The EURO model has been the best this winter with handling snow, so I’m showing what the latest run of the ECMWF has spit out for Denver and the snow totals are up! But I’m not buying it just yet. 
Again, we will have to account for where the storm comes in at and how much moisture it brings along with it, and how much wind it brings as well. We’d like to get the Upslope wind a little stronger so we increase our snow totals. 
I’m thinking that right now we’re looking at 1-4″ across the Metro will higher amounts to the south and to the west of town. 
It will also get very cold in Denver this weekend. 
Temperature Forecast for Denver through the 22nd December. 

This isn’t frigid or record-breaking but it is going to be much colder than the previous few days. 

Enjoy the wild weekend weather and keep looking for updates! 
~ Andy 

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12/11/19 UPDATE
It seems like we haven’t talked much about a lack of snow this season. It’s been snowy snowy snowy!

Snowpack across Colorado as of December 11, 2019

In fact, ALL areas of Colorado have seen impressive snowfall already this season. Statewide, we’re running 119% above the normal for this time of the year. This incoming round of snow will add to this impressive snowpack, improve drought conditions across the region and also increase avalanche danger as well.

Upcoming Snow
The upcoming snow will come in 3 waves but there won’t be much time between each wave so it’ll seem like this is one very long-duration event. The first wave of moisture is already starting to move in.

IR imagery 

Take a look above. Notice the red arrows – that is the stream of moisture that is screaming into Colorado with 130 kt jet pumping in a lot of Pacific Moisture. This is a great set up for heavy snow, especially on the western facing slopes. Snowfall is already beginning in the high country and it will continue through Friday night with varying rates of snowfall throughout. There will be a slight lull Friday PM before another burst of energy spills in.

Winter Alerts

Winter alerts are issued for much of the western higher terrain. Areas in pink are where the most snow is expected to fall between now and Saturday.

The secondary and third burst of energy is a little bit more tricky just because of timing and actual track – on top of that, the models are different enough to leave me uncertain in some areas. Some to note: the current winter highlights are for this FIRST round of snow. There will be additional winter alerts posted for the remained of the snow expected this weekend.

WIND
This will be an extremely windy storm as well. Gusts on some of the mountain passes could exceed 70 mph. More commonly, 30-50 mph winds will be felt.

FOR DENVER
Denver is going to miss out on much of the action until we get to Saturday, Sunday, Monday. There’s a little issue with timing that needs to be ironed out but ultimately, Denver *may* see impacts from the second and third burst of snow. The first round of light snow may move into the Front Range for Saturday when light precip could fall. That final burst of energy is the one worth watching closer. Timing and exact track or still up in the air but overall, models are suggestions that Denver could end up with some decent snow by the end of the day on Sunday. Some models are suggestions 4-6″ across the city. Other models are suggesting a trace-2″ is possible. So, obviously, impacts will vary depending on the final outcome.

Denver is also going to see windy conditions on Friday when winds could gust to 45 mph.

EURO Model through Sunday 

This is a look at the 06Z run of the ECMWF. It has been handling the winter weather the best this year. It has a solid 4-6″ across Denver by Sunday evening. It also has 1-2 FEET of snow for the mountains. The mountains, by the end of the weekend, could get up to 3 feet of snow! More commonly, 18-30″ of snow will be seen in the high country.

Denver, I can’t put a definitive number down yet as to how much snow will fall but expect wintery conditions this weekend with Saturday and Sunday being a little snowy at times.

~Snow or shine
  I’m Andy Stein

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