Colorado Weather Forecast #129: Oct. 5 - Oct. 10, 2021

Weak storm Wednesday, stronger storm this weekend, potential for Denver's first snow of the season next week.

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Updated Mon Oct 4, 2021 11:20pm MST | Published Mon Oct 4, 2021

By Thomas Horner

Note - OutThereColorado Article Reference

OutThereColorado posted an article which referenced and misrepresented this forecast. First off, we have a newer forecast here. Go and read it! Second off, we’d like to point out some mischaracterizations in the article which are objectively different than what we stated in this forecast.

“The prediction also mentions that while a cold front is on the way, lack of precipitation could be the biggest factor in whether or not this Front Range snowfall occurs.”

  1. Our forecast never mentioned the word “cold front” in regards to the potential for snow next week.

  2. Our forecast mentioned the lack of moisture potentially being the biggest factor for snowfall, which is not the same as precipitation (available moisture in the atmosphere). Implying that our forecast states that “snowfall would be limited by a lack of precipitation” is a bad look for us.

“The forecasting service states that Denver has a 10 to 20 percent chance of snow accumulation during a storm that’s set to hit the Front Range next Wednesday, October 13.”

  1. We never stated that “Denver has a 10 to 20% chance of snow accumulation.” We stated that a single weather model had that percent chance of snow, as a reference, without any endorsement.

  2. We specifically mentioned the uncertainty of this event occurring and did not imply that “a storm [is] set to hit the Front Range next Wednesday, October 13.”

Thank you to all of our readers and supporters who enjoy a more nuanced, statistical approach to weather forecasting! And welcome, newcomers! As always, feel free to engage with us on social media (you can also comment on these articles) with feedback and questions.


Summary

After another warm day on Tuesday, we’re looking at a weak storm on Wednesday, a stronger storm this weekend, and the potential for Denver’s first snow of the season next week.

Tuesday

  • Warmer and dry.
  • Weak storm impacts south/west Colorado by late Tuesday evening / night.

Wednesday

  • Weak storm impacts the Colorado mountains.
  • Cooler, snow levels down to about 11,000ft.
  • Light to moderate precipitation which wraps up by morning. Heaviest in the San Juans. Little to no precipitation east of the Divide until the afternoon.
  • Isolated thunderstorm development across central Colorado and along/east of the Divide in the afternoon.

Thursday

  • Warming.
  • Isolated light afternoon showers.

Friday

  • Warmer.
  • Stronger storm impacts south/west Colorado by the evening/night.

The Weekend

  • Colder.
  • A few waves of rain/snow.
  • Snow level down to 8,000-9,000ft.
  • Accumulations of 2-7” across the higher elevations of Colorado, generally, with some melting.
  • Gusty in the mountains, especially on Saturday morning.
  • Minimal impacts for the urban corridor besides a cooldown.

Current Conditions

Our storm cycle wrapped up for the weekend, with some decent snow totals at elevation, though much of it has melted out. Based on observations and modeling, we still see a dusting in the Front Range and a bit more snow in the Sawatch, Elks, and Mosquito range. The southern San Juans did pretty well with this last cycle and could have some deeper areas of snow.

You can just barely make it out on today’s visible satellite imagery:

(via College of DuPage)
(via College of DuPage)

Here are some shots from a quick go at the Four Pass Loop this weekend:

Sievert Mountain (Thomas Horner)
Sievert Mountain (Thomas Horner)
Maroon Bells (Thomas Horner)
Maroon Bells (Thomas Horner)
Treasury Mountain (Thomas Horner)
Treasury Mountain (Thomas Horner)
Trail Rider Pass south side (Thomas Horner)
Trail Rider Pass south side (Thomas Horner)
Snowmass Mountain (Thomas Horner)
Snowmass Mountain (Thomas Horner)

Forecast Discussion

Colorado is now beneath some mid-atmospheric ridging, which has brought warm and dry conditions across the state.

(via WeatherBell)
(via WeatherBell)

Mid-Week Storm

These will continue into Tuesday before a weak wave traverses northeast through the region.

(via WeatherBell)
(via WeatherBell)

The greatest impacts will be felt in the San Juans and Western Slope, with only slightly cooler temperatures in other areas west of the Divide. East of the Divide, such as in the Front Range urban corridor, impacts will be minimal besides some weak thunderstorm development Wednesday afternoon and evening.

West of the Divide, we’re looking at a band of precipitation pushing from southwest to northeast on Tuesday evening, reaching central and northern Colorado by early Wednesday morning and largely dissipating by sunrise.

Blended model guidance does not show this being a particularly interesting event:

(via Pivotal Weather)
(via Pivotal Weather)

Not a lot of cold air with this storm either, so the upper San Juans are only looking at a couple inches of snow at best, though this map may be underdoing it a bit:

(via Pivotal Weather)
(via Pivotal Weather)

Other areas of the state above 11,000-12,000ft. could see snow from any showers that wander through before warming back up a bit by Friday.

Weekend Storm

Let’s take a look at the Blend’s temperature expectations for Berthoud Pass over the next 10 days:

(via ESRL)
(via ESRL)

The bigger story is clearly the weekend, when a much more organized system comes ashore and impacts the western United States.

(via WeatherBell)
(via WeatherBell)

This storm would drop the snow level to 8,000-9,000ft., with precipitation occurring from Friday night (southern/western Colorado) to Monday morning (the Divide). The amount of available moisture is in question, with some drier air intruding on Saturday and potentially limiting the extent of precipitation. Regardless, this could be the snowiest storm of the season so far for northern Colorado, though it seems unlikely that southern Colorado will do much better than our previous cycle.

(via ESRL)
(via ESRL)
(via Pivotal Weather)
(via Pivotal Weather)
(via WeatherBell)
(via WeatherBell)

The higher terrain, especially near the Divide, would likely see gusty conditions on Saturday morning as the jet dives south into Colorado.

(via WeatherBell)
(via WeatherBell)

Areas east of the Divide would see very little precipitation, though high temperatures would cool to the 60s or low 70s for the plains.

Either way, expect a wet and chilly weekend across most of the state, with autumnal weather in the foothills and urban corridor.

Long Term

We’ve been discussing the potential for something to happen in the October 13th/14th timeframe (next Wednesday / Thursday) and this looks to actually be coming together. Ensembles are now showing a strong signal for a decent storm – likely the strongest of the season – and there is the potential the setup could bring snow down to the Front Range urban corridor and high plains.

(via WeatherBell)
(via WeatherBell)

Right now, its most likely that this system would impact Colorado as an open wave, putting us in the jet left exit region (with southwesterly flow aloft) and tapping into some cold air (though its no arctic air mass). The biggest limiting factor appears to be moisture. The current Euro deterministic is not surprising, with the San Juans picking up 5-10” of snow and lesser accumulations elsewhere.

(via WeatherBell)
(via WeatherBell)

There are also more exciting solutions that are currently in play. For Berthoud Pass, the probability of this storm dropping more than 6” of snow is about 20%. In Denver, the Blend has a 10-20% chance of snow accumulation. The latest GFS run looks downright juicy, with a great setup for Front Range snow:

(via WeatherBell)
(via WeatherBell)

This would bring measurable snowfall to the Colorado high plains.

(via WeatherBell)
(via WeatherBell)

The GFS is notorious for putting exciting events in its 10 day forecast that don’t really pan out. Right now, the ensembles don’t support such a thrilling setup, but with the Canadian model also beginning to lean in that direction, we’re not going to ignore it either. Let’s not get too excited, but we’ll allow you to cautiously express some optimism over the potential for our first winter storm of the season next week.

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