Colorado Daily Snow

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By Joel Gratz, Founding Meteorologist Posted 5 years ago April 30, 2018

Snow on Wednesday & Thursday (May 2-3)

Summary

Winter will not go quietly as a storm will bring snow to all of Colorado from Tuesday through Thursday. The southern mountains have the best chance for 6-12+ inches. The remaining open resorts in the northern mountains could get powder, but amounts are much less certain. The best time to ski deeper snow will be on Wednesday in the south and Thursday everywhere.

Short Term Forecast

On Monday, a slow-moving storm is entering Utah, and this storm will wobble and swirl around for a few days, eventually bringing snow to Colorado from Tuesday through Thursday.

On Tuesday, expect showers. Snow accumulations will be random. A few mountains will get accumulations, but temperatures will be warm so snow will be confined to areas above 10,000 feet.

On Tuesday night, the first part of the storm should bring intense snow to the southern mountains with snow levels lowering to 7,000 feet by Wednesday morning.

On Wednesday, the storm will gain some strength as it crosses Colorado, and we should see snow showers during the day.

On Wednesday night, as the storm moves over northeastern Colorado, the northern mountains will have a chance to see intense precipitation. The only open resorts (Arapahoe Basin, Loveland, Mary Jane (Winter Park)) are located in the northern mountains.

On Thursday, snow showers should continue, though, with the high-angle sunshine of early May, snow may not accumulate very much even as snowflakes fall from the clouds.

What does all of this mean for accumulations?

Below is the probability that an area receives more than 0.5 inches of precipitation, based on 51 versions of the European weather model. This is precipitation, not snow, and only the higher-elevation areas will get the snow. This late in the season, 0.5”+ of precipitation should translate into about 6+ inches of snow. Image from weathermodels.com, and thanks to weather5280.com for posting this map and making me think of posting it here.

Notice that the highest chances for higher accumulations are in the southern mountains and east of the divide over the eastern foothills and plains near and north of Denver. Also, don’t get hung up on the exact placement of the pixels – this is a lower-resolution model that doesn’t perfectly capture the terrain in Colorado.

Translating the precipitation above to snowfall, the average of all 51 versions of the European model shows the following. The best chance of deeper totals is in the southern mountains and in the northeastern mountains. Image from weatherbell.com

Remembering the last storm, though, which underperformed our expectations in the northern mountains, I took a closer look at the snow forecast on Wednesday night in the northern mountains. Each image below shows a different forecast from the European model, with the image on the left being the most recent forecast. Look at the variability in the snow forecast for the area circled in red!

I want to learn from my mistake during the last storm, so, for the upcoming storm, I went deeper into the data, looking for the cause of the variability in the snow forecast over the northern mountains.

What I found was that of all the precipitation forecast in the northern mountains for the upcoming storm, about 50-60% of the precipitation will be driven by convection (localized, thunderstorm-like precipitation) and about 40-50% of the precipitation will be driven by the larger-scale storm.

This is a very important detail because the forecast of convective precipitation is much LESS certain than larger-scale precipitation.

Think about summertime thunderstorms – we often know that they will occur, but it’s virtually impossible to know exactly where they will occur. And thunderstorms can produce a lot of precipitation in little time, which means that one area can get a lot of precipitation while another adjacent area is nearly dry. Again, our current ability to predict the exact location of these thunderstorms is limited.

What this means is that it's a BIG deal that over 50% of the forecast precipitation over the northern mountains is forecast to come from convection.That massively lowers my confidence in the snow forecast over the northern mountains.

Conversely, in the southern mountains, only about 20% of the forecast precipitation is forecast to come from convection, meaning that 80% of the precipitation will be driven by the larger-scale storm. This increases my confidence in the higher snow forecast over the southern mountains.

Wrapping this together…

* I have higher confidence that the southern mountains will get 6-12+ inches of snow from Tuesday night through Thursday. The best time to enjoy the powder (not at resorts because they are closed) will be on Wednesday and potentially Thursday morning as well.

* I have much lower confidence that the northern mountains will get more than 6 inches. While these mountains could see some accumulation from showers on Tuesday afternoon and Wednesday, the best chance for precipitation will be on Wednesday night into Thursday. The best time to enjoy powder (Arapahoe Basin, Loveland, and Mary Jane are still open) will be on Thursday. Remember my discussion about a lot of this snow coming from convection, which massively decreases my confidence in the snow forecast for the northern mountains. Within the northern mountains, areas closest to and east of the divide, at the higher elevations, likely have the best shot for the deepest snow. Models consistently show Cameron Pass as getting higher amounts of precipitation

Extended Forecast

I do not see another cold storm with widespread snow in our immediate future.

Thanks for reading!

JOEL GRATZ

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Geography Key

Northern Mountains
Steamboat, Granby, Beaver Creek, Vail, Ski Cooper, Copper, Breckenridge, Keystone, Loveland, Abasin, Winter Park, Berthoud Pass, Eldora, Rocky Mountain National Park, Cameron Pass

Along the Divide
Loveland, Arapahoe Basin, Winter Park, Berthoud Pass

East of the Divide
Eldora, Echo, Rocky Mountain National Park, Cameron Pass

Central Mountains
Aspen, Sunlight, Monarch, Crested Butte, Irwin, Powderhorn

Southern Mountains
Telluride, Silverton – north side of the southern mountains | Purgatory, Wolf Creek – south side of the southern mountains

About Our Forecaster

Joel Gratz

Founding Meteorologist

Joel Gratz is the Founding Meteorologist of OpenSnow and has lived in Boulder, Colorado since 2003. Before moving to Colorado, he spent his childhood as a (not very fast) ski racer in eastern Pennsylvania.

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