Wednesday and Thursday should both be mostly dry with a small chance of an afternoon shower. Then a slow-moving storm will stall near or over Colorado from Thursday night through Tuesday and it should bring at least 10 inches of snow to most mountains three feet or more in the southern and eastern mountains. Powder days are likely this weekend but I still have little confidence in isolating the times of heaviest snow.
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Showers popped up during the afternoon and evening on Tuesday and this resulted in a dusting to an inch or two at some areas (Vail snow report = 2” on Wednesday morning).
We’ll lose some moisture and energy on Wednesday so look for a drier day. I still can’t rule out a few showers during the afternoon and evening, though.
Most of Thursday should also be dry, though as our next storm approaches from the west, the wind will become gusty during the midday and afternoon hours, and we may see a few late-day showers as well.
Then, a slow-moving storm will essentially stall near or just to the south of Colorado from Thursday night through next Tuesday, and this means that some parts of Colorado could get snow for five straight days!
As of Wednesday morning when I’m typing this, our upcoming storm is swirling over the northern Pacific Ocean, just west of Washington State. You can clearly see the counter-clockwise swirl in this water vapor satellite image.
Finally, as of late Tuesday night, all weather forecast models are now generally on the same page and mostly agree on the storm’s general track and precipitation trend.
We should see an initial round of snow late Thursday evening into Friday morning, and then waves of snow (with breaks in between) will push across the state from Friday through Sunday, with lighter snow showers lingering through Monday and perhaps even into Tuesday.
Total precipitation accumulations will be impressive with this storm, and should range from 1.0 inch to upwards of 4.0 inches in southern and eastern Colorado. For perspective, the average annual precipitation in the Denver area is about 18 inches, so this storm could bring 10-15% of the annual precipitation in just five days.
While the precipitation forecast from the American GFS, European, and Canadian weather models all show the same trend, the European model’s forecast looks the most reasonable to me.
I can’t show most graphics from the European model due to licensing constraints, so below I’ll show the Canadian model instead, which looks similar to the European.
Here is the Canadian model’s precipitation forecast from Thursday night through Tuesday.
And below is the Canadian’s model’s snow forecast from Thursday night through Tuesday using a snow ratio of 1 inch of precipitation to 10 inches of snow. This will be a somewhat warmer storm, so this ratio is reasonable, though I bet the actual snow ratios could be a bit higher (and therefore we’d see higher snow totals than what is shown).
This is going to be a long-duration storm, and the key to forecasting snow amounts is to look at the general setup and not delve too far into the details. This is because the models have no clue about the details of a storm like this and are not able to accurately time each wave of precipitation.
So, backing out to look at the broad, general setup, this storm will hang to our south, which means that the wind direction at mountain top will be from the south and the east. These directions favor the southern mountains and also areas near and especially east of the divide. This gels with the precipitation forecasts I showed above, which target the southern and eastern areas of the state with the most precipitation. When the model precipitation forecast agrees with the general setup, I have at least moderate confidence in the outcome.
Lastly, since we already talked about much of this precipitation coming in waves rather than one shot of steady snow, and since we know that the models are not able to accurately predict the timing of these waves 4-5 days out, it makes sense to look at the model ensemble. A model ensemble means that the model is run many times (25-50) with slightly different factors, and then we can take an average of all of these model runs.
The graphic below shows the European model’s precipitation forecast from Wednesday morning through the next 10 days. The green bars are the ensemble forecast, which again is an average of about 50 models runs. There is a slight trend for the southern mountains (Wolf Creek) to see more precipitation then the central and northern mountains (Vail), while areas near and east of the divide (Rocky Mountain National Park) could see the highest precipitation amounts.
This is a lot of information to chew on, so here’s a quick recap:
We’ll see snow from Thursday night through next Tuesday.
The snow will come in waves. It will NOT snow steadily during the entire storm.
Total snowfall should be at least 10 inches for most mountains.
The highest snow totals should be in the southern mountains and areas near and especially east of the divide. These locations could get 30+ inches, and I wouldn’t be surprised to see reports of 40+ inches in the foothills west of Denver.
Temperatures should be cold enough for most of the precipitation to fall as snow for most mountains with a snow level around 7,000-8,000 feet.
The temperatures and snow level will be lower east of the mountains and there should be some accumulating snow in the Denver metro area. Impacts on the roads will depend on when the snow falls – nighttime will offer cooler temperatures and more likely travel impacts, though any wave of heavier snow will produce rapid accumulations.
The best powder days in the mountains will likely be on Saturday and Sunday, though the exact timing of the best powder depends on the exact timing of the waves of heavier snow, and I have zero confidence about this.
After this storm, we should see dry weather from about Wednesday April 20 through about Tuesday April 26th, and then we could experience yet another strong and slow-moving storm sometime around April 27th.
Thanks for reading and get ready for a fun five-day storm!
Steamboat, Granby, Beaver Creek, Vail, Ski Cooper, Copper, Breckenridge, Keystone, Loveland, Abasin, Winter Park, Berthoud Pass, Rocky Mountain National Park, Cameron Pass
Along the Divide
Loveland, Abasin, Winter Park, Berthoud Pass
East of the Divide
Eldora, Echo, Rocky Mountain National Park, Cameron Pass
Aspen, Sunlight, Monarch, Crested Butte, Irwin, Powderhorn
Telluride, Silverton, Durango, Wolf Creek (Telluride and Silverton are on the northern side of the southern mountains)