Highpoint Weather Blog

Forecast Discussion

Hello everyone and apologies for another extended break. The end of the year has brought forth a cacophony of illnesses, project deadlines, etc. and to put it simply -- props to all of you who are getting outside or even just getting acceptable amounts of sleep. This is a side gig so when life gets crazy we have to take a step back from this.

Anyways, though things haven't eased up just yet, this incoming storm has generated quite the buzz so we'll get a few words out on it.

Setup

From a larger scale perspective, a powerful low pressure system is currently coming ashore on the Pacific Coast and is expected to track eastwards across the Rockies, bringing snow to much of the western United States. Some areas are expected to see copious amounts of snow, such as the Sierra Nevadas, which have feet of snow forecasted for the next couple days.

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For Colorado, the system is moving a bit too quick and tracking a little too far north for this to be a monster storm, but powder days are likely across the state on Tuesday and Wednesday, and even Thursday for some northern areas.

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On the Front Range, chances are high that winds will be predominantly downsloping and thus snow totals along the I-25 corridor are only expected to be modest.

For the high plains in northeast Colorado, southeast Wyoming, and the Nebraska panhandle, snow totals will likely be more significant and near-blizzard conditions are on the table as the system undergoes lee cyclogenesis after crossing the Divide.

Regardless of snow, the entire region will experience a pronounced cooldown that should last the entire week, especially with chances for reinforcing shots of colder air on Thursday and the weekend.

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Still, the storm isn't too far off from being significantly stronger -- a decent slowdown or a more southerly track could change the forecast quite a bit for the Front Range and other areas of Colorado.

Let's consider the current deterministic run of the Euro -- this has surface low pressure just a bit too far north for the system to strongly impact the Denver metro area:

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However, its ensemble actually favors a more favorable southerly track:

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That more southerly track is the difference between 1-4" (current forecast for the Denver metro area) and 4-8".

Timings

As mentioned, this system could end up slowing down which would push back the start and end of snowfall by several hours. But as it currently stands, timings roughly look to be this:

Snow starts in western Colorado by 12am Monday.

On Monday morning, southwesterly flow works decent moisture into the state, resulting in heavy snow for parts of the western mountains. The San Juans -- particularly Wolf Creek -- are favored.

Snow reaches the central mountains and Divide by noon or the early afternoon.

A cold front sweeps down the Front Range / I-25 corridor on Monday afternoon.

Snow in the central and eastern mountain ranges becomes heaviest on Monday night.

The best chances for snow along the I-25 corridor are also on Monday night and Tuesday morning.

In the mountains, northwesterly flow continues along and north of I-70 from Monday night and quite possibly through Thursday morning, though dynamics and moisture may not be that robust.

An animation of atmospheric moisture captures these timings -- the initial plume of moisture with southwesterly flow on Monday morning, then drier wraparound northwesterly flow continuing into the week:

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Compare a meteogram for Berthoud Pass and Telluride airport -- Telluride has snow starting earlier, but very little after the initial wave.

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Berthoud Pass has a good chance of seeing light and moderate snowfall after the main event, even into Thursday morning.

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Snow Totals

The current amount of uncertainty in the track of the system will likely lead to substantial swings in the forecast. Here are some maps, which notably only go through Wednesday morning (the northern mountains will likely continue to get snow after that).

By looking at a probability map we can get a good idea of the magnitude of impacts for various areas:

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The maps below have labels showing the spread of snow forecasts from most weather models. It would fairly unlikely for final totals to be outside of these ranges -- but these continue to shift as more data comes in. The higher the spread, the higher the uncertainty.

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Thinking more broadly, the best skiing conditions in the western mountains may be during the day Monday (storm skiing) or Tuesday morning.

For the central and northern mountains, such as Summit County and the Park Range, Tuesday and Wednesday mornings should be nice.

Snow could hang on through Wednesday as well, with potentially another 4-8" in the Park Range for Thursday morning or 2-6" in the Summit County area.

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Next Weekend

Another weaker wave is likely this weekend which will keep us cold -- but this may not bring much snow if any. Right now, that's looking to be on Sunday if it does occur.