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Forecast Update | Mar. 12–15, 2021

Another update on expectations and totals for the storm this weekend.

Header image: Thomas Horner

How are we doing so far? Read our latest storm update here.

Again, just to reiterate, please read our article Snowpocalypse or Fauxpocalypse? A Guide to Powerful Spring Storms on the Front Range if you haven’t already.

Our storm system is currently crossing into Arizona and the weather east of the Continental Divide in Colorado has really started to deteriorate.

(via College of DuPage)

Another day of weather model adjustments have brought excitement and disappointment. While they’ve been entertaining to watch, our forecasting has been done with a very steady hand. Our expectations are largely unchanged from a couple days ago, as we have been careful to not get particularly hyped on this storm.

Consider the GFS runs today, which have continued to spark fervent discussion in forecasting circles due to its abysmal snow totals and high temperatures in Denver:

(via WeatherBell)

Meanwhile, the ECMWF has plugged right along in its consistent guidance for a more interesting event:

(via WeatherBell)

The models run-to-run don’t impact our forecast that much. Large changes in the ensembles do, and these haven’t really changed, besides some movement in the GEFS which we’ve weighted lowly anyways.

Thus, our expectations for this storm remain more or less the same. We think a significant “boom” or “bust high” is more unlikely than ever, but it could still happen. Conversely, the potential for a dud or “bust low” is notably higher, but we believe that we remain on track for a more “moderate” solution — where the Denver metro area gets a “modest” 1–2 feet of snow and the foothills get 2–4+ feet.

Again, we’re hoping you’ve been following along with our articles that have described the formation, anatomy, and impacts of these kind of storms, so that you know why forecasters across the board are struggling to hammer out more specific totals and why we’ve been careful to mostly talk about the storm in terms of its general impact. We are fully expecting some surprises, and perhaps, some disappointment.

Also, one thing that we probably didn’t make explicit enough was that the timetable of the storm was pushed back by about 12 hours once the GFS moved off a more progressive solution a couple days ago. Snow wont really start in the metro area until well after midnight (e.g. Saturday morning), and probably not become strong until the afternoon, with the storm wrapping up on Monday morning.

With all that said, lets forecast some things we can be fairly certain of:

Travel between the Front Range and the mountains is going to be very difficult, if not outright impossible at times

Conditions wont be as bad west of the tunnel, but likely still be pretty terrible at times until you get west of Vail Pass. With the heaviest snowfall occurring later on Saturday and well into Sunday morning, be careful if you’re thinking of heading up to the mountains. You may not be able to get back down if you make it up on Saturday morning, due to closures for accidents, safety, and avalanche blasting. GoI-70 suggests closures are highly likely between Saturday afternoon and Sunday afternoon.

Conditions should be incredibly difficult as soon as you get up the hill west of Golden. Speaking of skiing…

The mountains will likely not pick up as much snow as weather models and weather apps are calling for (even ours!)

This is just how these sorts of storms go. In general, these tend to be significantly overforecasted, with final totals often disappointing. When we look at historical analogs for storms similar to these, we don’t see snow totals much higher than a foot of snow west of the Divide — accumulations are often in the single digits.

That said, the amount of moisture and energy in these systems cannot be ignored, and if things come together in the High Country, there is the potential for very high totals. We just don’t think it’s likely, and want to keep your expectations in check so that you don’t brave awful driving conditions and huge lift lines for 4" of snow. If we do see some epic powder reports — well, we’re sorry, but trying to be realistic here.

Snow will be wet and heavy in the city

This will be a major factor that could make or break the forecast (and make shoveling difficult). Snow will melt and compact quite a bit, especially on Saturday, which certainly effect reporting of accumulations.

There will be bust highs and lows everywhere

Wherever the dry slot sets up is going to bust low. Consider this run of the HRRR:

(via weathernerds.org)

If this verifies, northeast Colorado would report pretty paltry totals from the storm, while 30 miles west on I-76, we could be looking at our expected 1–2 foot total.

We also worry about downsloping off the Cheyenne Ridge (lower totals in Fort Collins and Loveland) and the foothills, or the presence of warmer air than expected.

Conversely, the presence of a barrier jet, local terrain features, colder air, stronger bands of snow, the TROWAL, etc. could cause relatively small areas to bust their forecast high — potentially by a lot.

Overall, our forecast is a rough expectation but we are sure there will be some interesting reports across the board when all is said and done.

Timings

On the Front Range, snow will really get going on Saturday morning and intensify rapidly into the afternoon.

(via ESRL)

Snow will remain consistent but begin to taper off as we get later into Sunday, before only pockets of light and moderate snow remain by Monday morning.

Forecast

Our forecast thus remains largely unchanged from yesterday. Notable highlights include:

  • Denver County and eastern suburbs: 12–18" (bust low potential as you go east)
  • Western and southern Denver metro: 18–24" (bust low potential as you get closer to I-25)
  • Foothills and high terrain east of Divide: 2–3ft with pockets of 4–5ft possible
  • Divide resorts (A-Basin, Loveland, Winter Park): 7–15" (bust high potential)
  • Most other resorts: 6–12", generally — mostly some bust high potential

For a map, we like how the latest HRRR looks overall, but don’t read into it too much:

(via weathernerds.org)

Here are our updated tables. Note that the forecasted totals are handwritten by us, and may not line up with the probabilistic guidance (the percentages) — those are created with a statistical post-processing of weather models.

Note that the San Juan resort forecasts have dropped since yesterday, as we’re not including today (since today is over) — we’ll see how they did tomorrow morning.

Written by
Thomas Horner (@thomaschorner)

Website and app with automated, high-resolution forecasts for mountains, climbing areas, and ski resorts (+ backcountry) with elevation switcher, uncertainty visualization, and more:
https://highpointwx.com

Frequent updates, graphics, and general stoke:
Twitter / Instagram / Facebook: @highpointwx

If you enjoy our forecasts and/or website, please consider becoming a Patron to help keep the lights on. Thank you!

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Weather forecasts and articles for the recreating in the Colorado high country — mountains, ski resorts, and crags.

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Highpoint Weather Forecasting Team

Highpoint Weather Forecasting Team

The Highpoint Weather forecasting team — weather nerds who like to play outside.

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