Wildfires

On Friday, fire activity was much lower due to colder temperatures and light winds.

However, on Friday night and early on Saturday morning, wind speeds increased and temperatures warmed, and the East Troublesome Fire and the Cameron Peak fire appear to be much more active. This increase in wind speed was well forecast and the fire growth now on Saturday morning is what we were concerned about. Most major wildfires have dedicated meteorologists who provide weather information directly to firefighting teams, so this increase in wind speed and fire spread was not a surprise to the teams on the ground.

The fire growth now on early Saturday morning is apparent by seeing the smoke plume on radar and also by using heat-tracking satellite images. I am not going to post these radar and satellite images because they will likely be out of date within an hour (the fires will keep moving) and also because these methods of fire detection are useful but not perfect when trying to identify exactly where the fires are.

For a slightly geeky but useful overview of the satellite hotspot data that some of you might be tracking using Captopo or GaiaGPS or a host of other online maps online, here's a quick and readable thread to help understand the imagery that you're seeing. The satellite hotspot data is made freely available by the government so the maps showing this data are ubiquitous, but you need to understand the limitations of the data, and that quick thread will help.

For official information about evacuations and fire locations, follow local emergency managers.

For a mix of official and unofficial information, search the appropriate hashtag on Twitter (#EastTroublesomeFire and #CameronPeakFire). 

The wind forecast around both the East Troublesome and Cameron Peak fires is for strong winds from the west on Saturday, then winds slow between Saturday 6 pm and Saturday midnight, and then winds reverse and blow from the east by Sunday morning or midday.

Saturday is going to be a very difficult day due to these winds and the potentially rapid growth of the fires. Best wishes to everyone that is working the fires and everyone affected by the fires. We just need to make it to Saturday night to get a reprieve.

Uplifting image

Temperatures on Friday were cold over the northern mountains and snowmaking was ongoing at many mountains. Here is Parker the Snow Dog at Loveland supervising the snowmaking crew. Good job wearing eye and ear protection, Parker!

Snow Sunday and Monday

I confess that I became obsessed with checking all of the updated model data for this storm over the past 24-36 hours. I was obsessed because models were still offering significantly different forecasts and I was trying to figure out the signal through the noise and how to present that information.

Here are a few summary bullet points and then I'll get into more details below.

• The storm will bring snow to most mountains with 5-10 inches on average and a few spots getting into the 10-20 inch range.
  
  
• Most factors are working against significant snow and only one factor is positive for significant snow. This means that I am keeping my expectations on the lower side.
  
  
• The snowfall comes at a time when we desperately need it to stop fire growth, though with dry weather returning after this storm we may not be able to put our wildfire risk to bed.

The American GFS model is a little faster and weaker with the storm and the European and other models are a little slower and stronger with the storm.

The CAIC WRF below seems to split the difference and the latest forecast looks reasonable (for those of you model watchers, don't trust just one forecast from one model, even high-resolution models like the CAIC WRF because this model too has flip-flopped a lot over the past day).

Saturday night: Snow stays mostly north of Colorado

Sunday: The band of intense snow stays near and north of I-70. This is the best time for intense snowfall over the fires and Steamboat.

Sunday night: The band of intense snow hits the I-70 mountains and the central mountains around Aspen and Crested Butte and Monarch. Also on Sunday night, watch for strong east winds behind the band especially just east of the divide around the East Troublesome Fire and at Steamboat where there could be another downslope wind event though hopefully not as strong as the one in September.

Monday: Intense snow is possible over the southern mountains.

 

Monday night: The snow mostly moves out of Colorado.

As I mentioned earlier, the thing that jumped out at me when looking at all the models is that despite the lovely snowy forecast maps, most factors are not aligning for intense snowfall.

• The wind direction will not be favorable for most mountains.
  
  
• Temperatures will initially be warm, then eventually too cold for big snowflakes. The time of perfect temperatures will be somewhat short-lived.
  
  
• The best combination of wind direction and energy will be over the southern part of the southern mountains where a south wind is favorable. If the storm slows and strengths a bit, this area could see deeper totals. 

The only factor that is in our favor for intense snow is the jet stream which will create a narrow band of intense snow. This positive factor can overwhelm the other negative factors for a while, which is why we'll see healthy snow totals.

Despite the varying forecasts in the models and the factors working against us, the reason I am reasonably confident that most mountains will see 5-10 inches of snow and some could go over 10 inches is the simple math of the snowfall rate under the band of intense snow and the time it takes the band to move.

If the snowfall rate under the band is 1-2 inches per hour, and the band hits most mountains for 5-10 hours, then this equates to at least 5-10 inches and a few spots could go over 10 inches if snowfall rates are on the high side or if the band stalls over a location.

In storms like this, where most factors are working against us, I like to keep expectations low, so the 5-10 inch range feels good. That said, with a narrow, intense band of snow, some mountains could get a lot more snow and there could be road closures if/when snowfall rates push above 1 inch per hour.

I hope this analysis was helpful, and thanks for digging into the details with me.

For next week, Monday will be a very cold day with snowmaking possible for most of the day and intense snow over the southern mountains.

Then the rest of next week will become warmer each day and the weather should stay dry.

Then the outlook through the first week of November shows dry weather with temperatures near or warmer than average.

This is not a very favorable long-term forecast, though temperatures early next week should be cold enough for crews to make a lot of machine-made snow and it's possible that Loveland or Arapahoe Basin will open a run in late October or early November (this is just a guess as I have no inside information).

Thanks for reading!

JOEL GRATZ

PS - We just released a new All-Access subscription. It's a Group Subscription that's only $10/person/year for four people. It works just like a family plan on Netflix or Spotify, for example. You sign up and then invite three friends or family members or complete strangers that you want to be friends with. Each person gets their own list of favorite mountains, customer alerts, etc. If you already have an All-Access subscription, you can upgrade to the Group subscription in just a few clicks. As an incentive to try it out, our friends at Powder7.com ski shop are giving away a helmet + goggle combo and the only thing you need to do to enter to win is to be an All-Access Group subscriber by October 31st. So sign up now:-) Read more info about All-Access Groups and sign up.

PPS - I'll be chatting about the forecast and answering questions on Youtube Live on Wednesday, October 28th. Mark your calendar:-) More details soon.

Geography Key

Northern Mountains
Steamboat, Granby, Beaver Creek, Vail, Ski Cooper, Copper, Breckenridge, Keystone, Loveland, Arapahoe Basin, Winter Park, Berthoud Pass, Eldora, Rocky Mountain National Park, Cameron Pass

Along the Divide
Loveland, Arapahoe Basin, Winter Park, Berthoud Pass

East of the Divide
Eldora, Echo, Rocky Mountain National Park, Cameron Pass

Central Mountains
Aspen, Sunlight, Monarch, Crested Butte, Irwin, Powderhorn

Southern Mountains
Telluride, Silverton – north side of the southern mountains | Purgatory, Wolf Creek – south side of the southern mountains