An Over-Performer? Quick Peek at Latest Data Suggests Maybe So

Updated: 10:07pm

If latest data proves correct, we may have an over-performer on our hands, with the likelihood of this system busting high (>4” for Denver) rather than low (<2”) appearing more, and more likely. Generally speaking, however, we still like where we are. That’s 2 - 4”+ (locally higher amounts possible) for downtown Denver and the northern urban corridor, 3 - 6”+ east/southeast of I-25, 3 - 6” for the Front Range foothills, and 3 - 7”+ across the northeast Plains.

Below is the forecast we released earlier today, though note we’ve lowered the Bust Index from a 5 to a 3:

Winter Weather Advisory Upgraded to Winter Storm Warning
As of 9:30pm, the National Weather Service upgraded Denver to a Winter Storm Warning, and are now forecasting 5 - 10” of snow for the urban corridor. While we see that as a possibility – we continue to believe 5 - 6” will be the higher range if we “bust high” rather than 10”. Should heavy enough snow develop overnight, our forecast may go out the window completely and the NWS may end up correct. That said, It feels a bit late for us to make such a big adjustment, so for the time being we’re sticking with our earlier forecast, but emphasizing the fact that most folks are more likely to bust high rather than low.

Here is the latest HRRR model, suggesting 5” is very doable for Denver and all of the Front Range by 10am. Remember, this map is assuming a 10:1 ratio of snow to liquid, and we’ll likely be at >15:1 for this event. So, we do see how accumulations in upper single digits of inches could be possible should this storm perform to its full potential.

Weather5280 Models

The 00z GFS continues to suggest the greatest totals will be along and east of I-25, and actually looks a fair bit like our forecast, should higher amounts verify. Its initialization was much longer ago, however, and may be slow to catch up on things – if – indeed this storm is ramping up as some model guidance suggests. Here's the 15:1 snowfall forecast from the 00z GFS:

Weather5280 Models

We are currently sitting at 30°/25° at our station in Denver, with snow starting to develop along the Front Range at this hour. Coverage will continue expand over the next several hours, and become widespread during the early hours Tuesday. And, unlike previous snow events this season, with ground temperatures near or below freezing across the metro area, snow is likely to stick, including to paved surfaces, pretty much from the get-go. Bundle up in the morning, as the HRRR has most locations in the teens and low 20s by 7am -- with wind chills even colder.

Weather5280 Models

Any way you cut it, the timing of this snowfall will likely have big impacts on the morning commute. Please plan to give yourself extra time in the morning, and avoid traveling across northeast Colorado and west into the higher terrain on Tuesday if possible. The combination of wind, heavy snow, and reduced visibilities will make travel treacherous.

If this system really delivers 5 - 10" of snow, we'll accept the forecast bust and enjoy it! It's been a while since we've had a true over-performer, so... we'll see!

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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