Fresh snow, clean air on the way (Thursday AM update)

Thursday, January 24, 2013 at 7:36 am

Thursday AM update:

Everything still looks good from last night’s discussion so no need to update. Freezing rain is falling along the Wasatch Front this morning, making for a treacherous commute. Drive safe and slow. Stay home if possible. Update tonight.

Wednesday PM:
I was hoping things would become clearer this afternoon and for the most part they have. But this is still a very complicated pattern so it might sound confusing. I’ll break this down into three parts…

Part 1 will move into the area tomorrow morning… this will bring a round of snow to the high elevations of the Wasatch with rain/snow mix to the valleys. There is actually going to be a layer of well above freezing temps above the lower valleys. This will cause rain to fall that may freeze after entering the cold pools on the valley floor. Or it could turn to snow or sleet. Very difficult to forecast. But the NWS can focus on the valley details… For skiing/riding purposes, we can expect 3-8″ in the Wasatch tomorrow. Could be a surprisingly decent powder day! 12z NAM, GFS, Euro, WRF all looked good and have thus bumped up the totals from this morning. This system isn’t very strong, but has plenty of moisture to work with so it won’t take much to fire up snowfall.

Part 2 is a wave of moisture that will move into mostly southern Utah on Saturday. Models have at times suggested that the moisture will be pulled far enough north to give the Wasatch a chance at some decent snow. Right now I’d expect Saturday to feature light snow with only a couple inches for the Wasatch with more significant amounts in the mtns of S. Utah. This moisture, having tropical origins, will push snow levels up from the valleys.

Part 3 is actually a series of disturbances that is part of one large trough. This will move into the area on Sunday and could bring periods of snow to all elevations Sunday-Wednesday. It will also clear out the inversions completely. This is the “part” of the forecast that looks most promising to deliver significant amounts as we’ll have decent moisture, decent dynamics, cold temps and a long duration event. Still too early with too many questions to start talking amounts but I’m not afraid to throw out at least the possibility of significant snow. We certainly could use it.

More tomorrow AM . . .


Lots to talk about today so let’s get right to it. The first system will start breaking down our ridge today and we should see an increase in high level clouds and a few breezes. Unfortunately, it looks doubtful we’ll get the winds down to the valleys enough to blow out the stagnant air. The cold front will weaken as it breaks down the ridge but when it moves through Utah tomorrow morning, it would have enough moisture left for light snow in the mountains. I expect 1-3″ for the Wasatch. The lower valleys will likely be below snow level, however with the cold air in place on the valley floor, what we might see is the precip re-freezing near the surface levels. This could mean a mix of snow, sleet, and freezing rain. Long story short, tomorrow morning’s commute could be interesting. Due to the faster movement of the front than expected 24 hours ago, I would think that tomorrow might be the better ski day rather than Friday with a couple inches of fresh snow possible. Not much, but still a nice change from the hardpack.

The next feature to affect our weather will be a secondary low lifting through Southern Utah late Friday and Saturday. Don’t think the Wasatch will see much from this but the mountains of Southern Utah could do quite well as it has plenty of tropical moisture to work with. Up north, we’ll likely see a few clouds and a chance for further snow showers during the day Saturday.

The final piece of energy is still being handled differently by each model. The GFS (and several other models) still hold on to the idea of a cut-off low dropping to our west late this weekend. This was the general idea first put forth by the Euro earlier this week. The Euro now, however, keeps the system as a more traditional consolidated trough that slowly works its way through the area between Sunday-Tuesday. The GFS would severely limit precip in the Wasatch if it holds and we’d likely only see light to moderate amounts of snow. The Euro, however, would bring more significant snowfall to the Wasatch. It’s going to be interesting to see the 12z runs of each model to see what direction they are headed. Either way, we’ll likely finally scour out the valley cold/smog pools. An afternoon update sounds good to keep everybody up-to-date.

Beyond Tuesday of next week it looks like we’ll ridge up again for at least a few days. This does not look to be nearly as dominant of a ridge and may break down by about the 5th or 6th of February. Of course, as always, looking this far into the the forecast is very speculative but it’s fun to do all the same. MJO looks like it’s really starting to enter favorable locations so hopefully a snowy February is in the cards. Stay tuned . . .


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14 thoughts on “Fresh snow, clean air on the way (Thursday AM update)

  1. Anonymous

    Thanks, WSF! Would you say the general momentum within models in last couple days are shifting more towards Euro view or GSF at this point? Or is that simply too hard to judge still?

    1. wasatchsnowcast

      It’s difficult because the models flipped so there isn’t really a trend. When the two main models (Euro and GFS) disagree, we often look to other global models to see where they stand. Right now, GFS has the most support. Euro has been more consistent however this season in the 4-6 day range. I think the 12z runs today will be very telling so stay tuned . . .

  2. Steve

    So, what do you think of the 12Z? To my untrained eye, it looks like it’s trending in wrong direction, but what do I know. Don’t know where to look for the Euro. Leaving tomorrow, so a bit anxious about what will happen in next few days. Thanks for your thoughts.

    1. wasatchsnowcast

      It shows slightly less overall moisture but seems to move the “bullseye” of QPF farther east, directly over the Wasatch. I recommend using the Precip_total parameter to view this. Viewing the forecasted QPF for the next, say, 140 hours will give you a good feel for how the models are trending. You can free outputs of the euro at several sites. A quick google search for ECMWF will return some good sites. Fool around with a few of them and you’ll find one that’s easy enough to understand. You generally have to pay to get access to Precip and some other outputs for the Euro.

  3. Matt

    Thanks, WSF. Is there any change in the outlook for Part 3 of this event? Any additional confidence that it will bring “significant” snow? HOpe so!

    1. wasatchsnowcast

      No real changes. At this point I think there’s a high chance for at least moderate snow with a fair chance for significant snow. Moderate is generally around a foot, significant would be 18″+. I’m going to do a full look through all the models this afternoon and see if I feel more confident with the system.

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