Colorado Weather Discussion #130: Oct. 6, 2021

Snow totals from Wednesday's wave, Denver's last 80+ degree day?, weekend updates, and another look at snow chances for Denver and the mountains next week.

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Updated Wed Oct 6, 2021 8:30pm MST | Published Wed Oct 6, 2021

By Thomas Horner

This is an update for our current valid forecast, please consult that article for more details about the future weather forecast.

Snow has fallen in the higher reaches of the southern and central Colorado mountains today, but as we expected, accumulations have been a dusting to a couple inches, with the largest impacts in the San Juans.

A weak Denver Cyclone made an appearance today, with cooler temperatures to its northwest. A convergence boundary associated with the cyclone was visible on radar:

(via Radarscope)
(via Radarscope)

Denver International Airport hit a high temperature of 85 degrees today – and this may have be the last 80+ degree day of the season. The Blend has highs just under 80 through Friday before we enter a stormier pattern starting this weekend and lasting through most of next week.

We’re still on track for one of our coldest storms of the year this weekend.

(via Pivotal Weather)
(via Pivotal Weather)

Moisture is limited, however. The most abundant moisture is available during Friday, when temperatures are warmer. Snow totals aren’t too impressive on most models, however, we would expect to see some reports of 4-8” in the higher reaches of the San Juans, central Colorado mountains (the Elks), and maybe the Flat Tops or Park Range. The lower bounds are still pretty low, especially below treeline, where appreciable snow totals are more on the unlikely than likely side.

The biggest story is the storm mid next week – around October 13. This is the real deal, and we’ve been watching snow chances for Denver creep up into the “somewhat likely” range, despite the GFS abandoning its prospects for a significant snow storm in the city. In the mountains, guidance is still all over the board, but the range of outcomes is pretty exciting.

Deterministic models have been going back and forth, as expected. Will next week’s storm be an open wave (no snow for the lower elevations)? Will it be a closed low centered over southern Colorado (nice cold upslope for Denver)? Some cyclogenesis further north (a few flakes for Denver)? All those options are still on the table. The GFS has not shown a strong upslope storm for the Front Range in its past few runs, but the Euro and Canadian models have largely flipped towards that scenario – still, the ensembles reign supreme in accurately conveying the uncertainty and potential of outcomes with the current data that we have.

Guidance from the Blend has been creeping Denver’s snow prospects up – we’re trending towards the real possibility that Denver could see some appreciable snow next week.

When bias/ground-truthing statistical algorithms are applied to the data, we see that the 75th percentile has an inch of snow for Denver – so prospects are looking decent. However, the most likely solutions still have Denver missing out on the flakes – but the trend is good if you want to see snow! For the mountains, we could see some really nice totals, but again, without having a good grasp on the storm track, it’s impossible to say who may win out with next week’s storm, though we’re leaning towards the San Juans. We’ll keep you updated!

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