A Very White Christmas (Thursday AM update)

Monday, December 24, 2012 at 4:59 pm

Thursday AM update:

Light snow continues to fall this morning and should continue throughout the day, especially on northwestward facing slopes. Snow should start to taper off this evening. Area resorts reporting anywhere from 6-20″ so far from this storm with the majority between 14-20″. The exception is resorts on the Park City ridge which are not favored by this type of pattern and have seen 6-10 inches. We should get 3-8″ (2-4″ Park City) today to bring storm totals to 10-24+”… Pretty close to what we were expecting but it would have been nice to see a little heavier snow rates.

Full storm wrap-up and extended outlook this evening . . . WSF

Wednesday PM update:

Light snow has been falling for much of the day in the Wasatch. Accumulations have remained fairly light with 1-5″ at the base of mountains and generally 4-6″ for mid-mountain and above. Of course, some places that are favored by a SW flow have seen more than others. Snow should gradually become heavier and continue for most if not all of the night and a good portion of tomorrow as well. Not feeling too confident in our 1-2 feet prediction at this time due to how light snowfall rates have been so far but we’ll see if it will start to pick up in intensity this evening. There’s a good chance we might end up with 10-18″ with up to 2 feet in the Cottonwoods instead of 12-24″ with up to 30″ that we were thinking earlier. With that being said, if things pick up nicely tonight and we can get a long-duration of at least moderate snow, we might still hit the earlier ranges. Time will tell.

We should clear out on Friday before the next system approaches on Sunday. This system is splitting and at best might bring a couple inches. Beyond that, the GFS made a dramatic change from strong ridging through the first week of January to bringing a system in about the 3rd of the month. We’ll have to see if this system is still in future runs before we buy into this idea. Overall, it looks like a much less active pattern as we head into 2013.


Wednesday morning update:

Happy Boxing Day! Warm advection precip began overnight and has been falling off and on. This is mostly light snowfall. Snow intensity will pick up this afternoon as the weak front approaches and should continue more on than off tonight and tomorrow. All accumulations look on track… 1-2 feet in the Wasatch with up to 30″ in the Cottonwoods and other west-facing slopes. Happy shredding!

Update in the PM…WSF

Christmas morning update:

Happy Holiday to all! Hope you are either spending the day with family or, if not, at least you are skiing. Better yet, perhaps you are skiing with your family! It is a beautiful bluebird day up there with light winds and plenty of fresh snow. We predicted going into the storm 6-12″ with up to 18″ in the Cottonwoods. 48-hour snowfall totals show anywhere from 7-10″ at northern resorts, 9-15″ at Park City resorts, and 15-21″ in the Cottonwoods. Brian Head and Eagle Point even got decent snow. So it looks like we got this one just about right, maybe ever so slightly under-predicted the snow, but we usually shave off a bit from the models to account for unexpected factors that can cause a storm to not deliver. December has so far been one of the most accurate months we’ve ever predicted. Model performance has been very good. As expected, we saw small systems for the first couple weeks of the month before the transition to larger storms around mid-month. It’s been spot on!

The next trough is already approaching the area as seen on this satellite image:


This will spread clouds into the area beginning this afternoon. The structure of this storm system is rather poor, but it has several factors going for it that will give us good, if not great, snowfall totals. The first is it’s slow movement which will prolong the snowfall. The second is the abundance of moisture that it will draw into the area ahead of the trough itself. This is called warm advection. Warm advection should start light snowfall in the Wasatch by around midnight tonight and continue until Wednesday evening before the front finally reaches the area. The slow moving front should bring the heaviest snow to the area Wednesday night. The third and final factor is there will be an extended period of a cold, moist flow behind the front on Thursday/Thursday night that will create orographic and perhaps weak lake effect snowfall throughout the mountains. Overall, what we’ll be left with is an almost 48-hour event. If we can just average .5 inches of snow per hour, we can pick up 2 feet overall. My guess is favored areas like the Wasatch can do even better than that. So, with that all being said, our prediction is 1-2 feet in the Wasatch with up to 3 feet possible in orographically favored areas (Cottonwoods).

For the valleys, this event should be all snow. The light nature of the storm will make travel not as bad as it could be, but off and on snow will definitely add up and late Wednesday/early Thursday, snow could be heavy at times so be careful. Valley snowfall could reach up 6″ with up to a foot on the benches.

Skiing will be great Wednesday-Friday! So get out there and enjoy!


What a difference a year can make! Last December at this time it had been almost a month since we had seen snow and we still had three more weeks of dry weather to go before winter finally arrived. This December we’ve seen one storm after another almost all month. Today’s storm came in exactly as we expected and accumulations have pretty much been on track with 6-12″ with more in the Cottonwoods. Storm is winding down and snow should continue off and on until about 9 or 10 tonight before tapering off completely at all elevations by midnight.

Tomorrow will be blue bird with blue skies and 8-18″ of new snow at Wasatch resorts. A great Christmas indeed! The break in the action will be short-lived however as the next trough begins to enter the area as early as Wednesday morning. Snow should pick up through the day on Wednesday and continue through at least Thursday night in the mountains with off and on snow falling in the valleys. The storm isn’t particularly strong but all models show it holding together well and tracking over a favorable area for Wasatch snow. The main quality that this storm possesses that will give us good accumulations is its slow movement. The prolonged period of snow generated by a moist, persistent northwest flow should really cause the snowfall to add up by the time things are said and done on Friday.

Still difficult to pinpoint exact amounts but right now it looks like 1-2 feet is a safe bet in the Wasatch with up to 3 feet possible in favored locations like the Cottonwoods. At this time, Thursday and Friday look like great powder days but with all the fresh snow out there — you’ll be able to find untracked lines each and every day this week. Merry Christmas and Happy Shredding!


P.S. Sorry if the posts are shorter than normal this week… Family is in town and there’s a lot going on.

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  • Peter Marcy

    You do an excellent job forecasting the difficult weather systems for our area! For the longest time I followed tahoeweatherdiscussion.com and altered it a couple days etc. based on my basic knowledge of weather patterns and forecasting (which worked well in many cases)! But once I found myself living full time in the wasatch range, I realized I needed to find a more accurate and centralized forecast. Eventually through hours of searching and looking at stupid weather sites I found wsf.com and instantly was hooked. I check it daily-3 times a day for those twice a day updates. Furthermore, I wondered if you were thinking/considering going national on your forecasting? From my experience in reading your blog, you do an excellent job of realistic forecasts for such a tough area. In checking in on the tahoeweather page, I found today that they have moved to a larger server on opensnow.com. I post this link: http://www.opensnow.com/forecasts to show the other major forecasters, as well as show the current void of a Utah forecaster! something to consider! merry christmas.

  • MG

    Merry Christmas! Getting to Utah for a week of skiing at snow bird/alta starting the 30th. Looks like some of the forecasting sites are calling for a period of ridging and dry conditions after this Thursday system , lasting well into the first weeks of January. How do you see the ridging situation panning out in the long term? Thanks!

    • It looks like we’ll have a break in the snow from about Saturday, the 29th, through the first week of January. Unfortunately, at this time it looks like this dry weather should last through the first week of the month. But this is what models are currently depicting and that may change so stay tuned.

      • MG

        Thanks, At least there is ample snow pack levels.Just happy to get out of the North East!

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