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Sunday October 21st 2012 10:52am MDT

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I spent a LOT of time this morning looking at all of the models and all versions of the models, and like most things in life, the best way to move forward is to compromise. The storm I've been talking about since last week is still enroute and should bring snow to Colorado from Wednesday night through Friday. But the details are super messy...

With each storm, there are some things meteorologists can be confident about, and there are some things that are filled with uncertainty. Most people don't quite understand that there's a distinction here. Many times, people focus on only one aspect of the storm and use this as a guage of whether the forecast was correct or incorrect. But this can be misleading.

There are a few components to a winter storm forecast. Location. Timing. Temperature. Wind. Snow. For the upcoming storm, I'm pretty confident on three of these things: Location, Timing, Temperature. The big question is snow.

For location, the areas most affected will be Aspen and north and east along the continental divide and onto the urban areas of the plains.

For timing, the cold front should arrive between about sunset and midnight on Wednesday night. Colder air and snow could stick around through Friday, though it's likely that there will be two periods of storminess -- Wednesday night into Thursday morning and again Thursday afternoon into Friday.

For temperature, the cold air will drop temps by 20+ degrees and it should get down to freezing for all the mountain bases and even the urban areas on the plains. If we get enough moisture and the storm can slow down a little bit, our cold temperatures will ensure snow will fall down to the lowest elevations.

And that brings up snow. I think a few inches is a good bet for areas north of Aspen and especially the I-70 area and further north. This snow should fall Wednesday night.

The bigger question for snow is what happens east of the divide, from the foothills out onto the urban areas of the plains. While the American GFS model was gung-ho about an upslope snowstorm during yesterday's model runs (there are four model runs per day, every six hours), it has backed off this forecast this morning. Thankfully, this less-snowy forecast is more in line with the other models, including the European (ECMWF). When models start to agree, my heart rate decreases just a bit. Of course model agreement on a 4-5 day forecast is no guarantee, but as the models start trending toward one another and I look for a compromise between the snowy GFS and the less snowy ECMWF, my gut forecast is that there will be snowflakes in the urban areas on the plains and also in the foothills east of the continental divide, and this could happen twice, on Thursday and again Thursday night or Friday. Right now I'd bet against a big snowstorm, but I do think many areas will look and feel like winter by the end of the week.

All this talk of Colorado weather should not distract from the real winner of this storm, which will be the Lake Tahoe region. Probably 1-2 FEET of snow will fall there with good accumulations even down to lake level. You might be jealous of their success, but remember they went for almost two months last season with no snow, so they're owed a little something, yes?! Check out Bryan's excellent site at TahoeWeatherDiscussion.com. In a couple more weeks' we'll be welcoming Bryan as a forecaster with Opensnow (we tested it out last season and the test went great!).

Finally, since The Weather Channel is naming winter storms but feels no need to cater toward skiers (and instead wants to focus on snow that disrupts life and travel in big cities, which is understandable as that's their demographic), Opensnow.com will take it upon ourselves to name storms that make skiers and snowboarders happy. On that note, please meet Elvira!

Elvira the winter storm

Here's the map of snowfall in the US for the next five days. Hint: the west is going to turn white!

JOEL GRATZ

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