Minor forecast adjustments as we await first flakes, heavy snow across Northeast Colorado tonight into Tuesday

Not too much change to the going forecast, only minor adjustments as we try to figure out what ultimately this thing is going to do. A Winter Storm Warning goes into effect at 8pm this evening, and will continue into Tuesday afternoon. From the National Weather Service in Boulder:

  • WHAT...Heavy snow expected. Winds gusting as high as 40 mph.

  • WHERE...From the Denver metro area and Castle Rock north to Boulder and Longmont, Greeley, and Fort Morgan.

  • WHEN...Snow will develop this evening and will become heavy by late evening. The heavy snow will continue into Tuesday morning, then diminish.

  • IMPACTS...Travel will become very difficult to impossible tonight. This may occur in areas north of Denver and near the foothills by mid evening, and will be a bit later across the rest of the area. Road closures and impassable side streets and rural roads are likely.

As has been the case for many days now, the highest confidence forecast with this system is north and northwest of Denver –– areas like Boulder, Loveland, Fort Collins, all have the potential to do very well with this system, as do foothill communities at higher elevations to the west of the northern urban corridor.

We will leave Denver in the 6 - 12" range as there's not enough reason to make big changes here. However, the city (especially say south of I-70) remains in the high bust potential zone. Could Denver end up more in the 4 - 8" range? Yes, it's on table and always has been. However, we aren't quick to change forecasts without very good support to do so, and for now too much high-end potential still there for Denver to make any changes.

Our biggest change was to pull the 8 - 14" range west a bit from our forecast yesterday, as data has trended toward a more upslope-heavy event, i.e. favoring areas at or against higher elevations along and west of I-25 vs those east across the Plains.

Here is a our latest forecast map:

Timing still looks good. Rain and snow are already showing up across the norther portions of the state, which is a trend that continues through the afternoon. Coverage and intensity increases as we head into Monday night, with the heaviest snow along the urban corridor still expected between 7pm tonight and noon Tuesday.

Here is the latest temperature, precipitation probabilities, and wind forecast for Denver. Surrounding areas follow a similar trajectory, with northern Colorado (Fort Collins) seeing PoPs a bit earlier, and Colorado Springs a bit later:

Again, despite our nerves around the Denver forecast, and our minor adjustment to totals north/northeast... overall impacts remain the same. This will be a significant storm for many communities across Northeast Colorado, and travel will not be advised overnight tonight and into the day Tuesday until the system begins to clear Tuesday afternoon.

The latest HRRR model shows pockets of heavy snow showers developing as early as mid afternoon for the areas north of Denver, before perhaps a brief pause before things get going in earnest tonight. We'll see if that materializes, but some potential for trouble spots already for your evening commute a possibility.

Here's it's latest forecast for 6pm this evening, heavy snow north of Denver:

By midnight we see snow becoming more widespread from Denver north, west, and east (even a little something moving through the Springs!):

By tomorrow morning it is still snowing up and down the Front Range, but the heavier snow is starting to work east:

With this particular model showing snow coming to an end for us by midday or early afternoon, a timeline that seems reasonable:

It'll be an exciting 24 hours. Please keep us posted how things shake out at your place in the comments below... and if you can avoid travel until tomorrow evening or better yet Wednesday, please do!

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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