Less than 24 hours ’til liftoff

Monday, November 5, 2012 at 7:46 am

Thursday PM update . . .

Winter Storm Watch in the Wasatch and Uintas is now a Warning, meaning snowfall is imminent. Winter Weather advisories hoisted for the valleys as well. All our predictions from earlier still look good for snowfall totals. NWS is now in line with exactly what we’ve been calling for since Sunday, 1-2 feet with more possible in favored locations of the Wasatch and Uintas.

Here is a look at total QPF as depicted by the NAM through the weekend:

As you can see, a large swath of 1-1.5″ of liquid precip is forecasted for the Wasatch. With snow ratios at 15-20:1 we can expect 15-30 inches of snow from this. GFS isn’t quite as bold so stuck with the conservative 1-2 feet but, yes, there is a possibilty for more than that.

Full update in the AM! WSF

Thursday AM update . . . .

We are now just one day out from the onset of precipitation. Everything is still on track and our previous discussions still stand as the going forecast. In fact, this has been one of the most uneventful weeks leading up to a system. Literally nothing has changed since we first started talking about the details of this storm over a week ago. The timing is still for the initial front to move in tonight with precipitation starting tomorrow morning and then continuing on and off with orographic lift and good instability moving through the area through Sunday morning. No need to change the original snowfall forecast we’ve been projecting for the last few days — 1-2 feet still looks likely for the high Wasatch with the possibility for more on northwest facing slopes and areas that may get enhancement from lake effect snow, including the Cottonwoods.

The valleys should also see widespread snow accumulations with 2-6 inches possible down to the valley floor with 5-10″ on the benches. Again, if an area gets under a decent lake effect band, they could locally see greater accumulations. This is most likely in Davis County and northern Salt Lake County on Saturday and Salt Lake Valley and Tooele Valley on Sunday morning.

This is a very cold system, which will allow snow to really pile up quickly. It will also allow resorts to make snow for at least four straight days. With that being said, it is not ideal for base building. It would be nice to have a little more wet snow on bottom but we’ll take what we can get.

A quick look beyond this storm shows us clearing out with a gradual warm up early next week. We then will have a chance for a weaker system on Thursday or so of next week with a possible stronger system next weekend. It doesn’t look like we’ll be returning to an extended period of dry and sunny weather anytime soon. And I don’t think too many of you will be overly upset by that. More tonight . . .



Wednesday PM update:

12z and 18z model runs were consistent, NAM looks very good for giving the Wasatch a good old walloping. This afternoon was the last warm and pleasant one we’ll have for a while with temps reaching over 70 at the SLC airport. We likely won’t see that again until the Spring. Tomorrow will be another warm day but won’t feel nearly as pleasant with cloud cover and winds picking up ahead of the front. Still expecting 1-2 feet in the high mountains with the possibility for more than that in places.

It all starts Friday!

Update tomorrow… WSF

Wednesday AM update (8 AM):

Today’s discussion is highlighted by the simple fact that everything is still on track. In a situation such as this, no news is good news. Last night the NWS hoisted a Winter Storm Watch for the Wasatch and Western Uintas. It was inevitable, just as it is inevitable that they will upgrade that to a Winter Storm Warning. WSF was curious to see what snow amounts they would forecast, as the NWS usually waits till about 72 hours out from the the event to make exact snowfall predictions, and their Wasatch forecast called for 1-3 feet. What this tells me is they are seeing the same thing as I am. Since Monday morning we’ve been saying 1-2 feet with more possible in favored locations. NWS is also seeing that 1-2 feet is a safe bet, but if we get an extended period of really good orographics and maybe some lake effect , as the models suggest we might, we might have a distinct possibility to hit 3 feet in places. It is highly likely that the valleys of Northern Utah will see some type of winter weather highlight. Whether it is an Advisory or Warning remains to be seen. The semantics don’t really matter though.

Last night’s 00z run of the NAM is finally in decent range for Friday. Yesterday, we were a little too far out for the NAM and it was showing Friday as mostly dry for Northern Utah. We knew this was just an issue with the model over-extending itself (NAM is a short range model), and sure enough, it’s latest run is now showing fairly vigorous energy moving into Northern Utah during the day on Friday. Precip may start as rain at the lowest elevations Friday morning but should turn to snow quickly. The mountains will see all snow and it should pile up on Friday with 6-12″ likely by nightfall at most resorts in Northern Utah. Like we mentioned yesterday, we think there may be a break Friday night as we wait for the best instability associated with the cold pool aloft to enter the area. This will happen on Saturday and we should see orographically enhanced and perhaps lake effect snowfall all day on Saturday and probably through Saturday night. This period could yield another 1-2 feet on top of what we see on Friday in the mountains. So how much total? This is the current thinking:

Wasatch Mountains above 7,000 ft: 1-2 feet with up to 3 feet in favorable locations
Wasatch Valleys/Front Benches: 6-12″
Wasatch Front Valleys: 3-6″

We will clear out on Sunday with only cold temperatures remaining. Ski resorts should utilize Sunday and Monday to make snow while it’s still cold. Models still hinting at a system moving in for the middle of next week but the best energy could miss us to the north and therefore it will likely be much weaker and probably warmer than the first system. We’ll look at that more in the coming days.



Tuesday AM update:

For the last 5 days or so models have been showing the front entering Northern Utah late Thursday evening and moving the SLC area around midnight. Now both the NAM and GFS are showing a delay in the onset of precipitation until late morning Friday. Not a ton of moisture with the initial front but could see a brief period of moderate to heavy snow in the mountains and lighter snow in the valley during the day Friday. There may be a break after the front on Friday evening before the instability and moisture associated with the cold pool move into the area. Friday night and Saturday we’ll see the best dynamics and the best orographics for widespread moderate to heavy snowfall. There will be a good chance for lake enhancement or a lake effect band downwind of the lake. Best guess right now would be east-southeast of the lake. Over southern Davis County and Northern Salt lake County toward Park City. We’ll have to monitor the lake effect situation as we get closer as it is notoriously difficult to forecast.

When we look at the two aspects of this system, the front and instability behind the front, we can split the system into two separate parts to make our snowfall predictions. The initial front on Friday looks like it will put down 4-8″ for the mountains and only a couple inches in the valleys. Then the cold pool on Saturday has potential to drop up to 6″ in the valleys with more than that possible under lake effect band if one sets up. The mountains will likely see over a foot of snow on Friday night-Saturday night time frame. There isn’t incredible moisture associated with the system. But the direction of the flow aloft will allow for good orographics and the cold air will create very high snow:water ratios so just 1 inch of liquid qpf will likely yield 18 inches of snow.

With all that in mind, by midday Sunday, WSF expects the following totals:

1-2 feet above 7,000 ft. (with possibly more in orographically favored areas or under lake effect band)
6-12 inches in mountain valleys / high benches of Wasatch Front
Up to 6″ on valley floors

Next week is still a little unclear but it’s looking like we may be clipped by another system mid-week however it looks weaker/warmer. We’ll keep our focus on the storm at hand for now.



Monday PM update:

00z model runs were slightly slower with onset of precip, so we may have to wait until later Friday morning before snow starts falling. Good news for morning commute.

Everything still looks good in the models. If anything, we think our snowfall totals from this morning could be low for the mountains. But until the NAM is within range to give us a more precise QPF forecast, going to stick with the conservative estimate of 1-2 feet. Exciting stuff! Update tomorrow AM….


We have now been talking about this system for close to a week. It started as, “Unsettled weather looking possible for the second week of November” and has become clearer with each passing day. For several days we’ve been confident in at least some snow falling for the Wasatch, but have been reluctant to make any exact snowfall predictions. But with incredible model to model and run to run consistency, it’s time WSF makes our first prediction.

Similar to the storm we saw a couple weeks ago here in Utah, this system will drop from the Gulf of AK down the coastline of British Columbia and the Pac NW over the next several days. We will be approaching record temperatures over the next few days prior to its arrival. The initial front will drop through the area on Thursday night and could fire up some thunderstorms. Pre-frontal winds on Thursday will also be strong. After frontal passage, snow levels will quickly drop to all valley floors. Snow should continue Friday – Friday night – Saturday in the mountains with off and on snow showers in the valleys. Still some questions with regard to direction of the flow and how that will affect the amount of orographic lift we see in the mountains. Also questions with regard to if, where, and when a lake effect band may set up — we may have to wait for the NAM to get in range before we look at that. GFS tries to cut off precip a bit earlier than the EC with most precip ending by sundown on Saturday whereas the Euro keeps at least snow showers going through the day on Sunday.

You may have gathered that while confidence in a major pattern change to cold, snowy weather is extremely high, the confidence in the small scale details within the system are low and therefore make it difficult to predict snowfall amounts. But by finding a common middle ground between models, these are what WSF believes we can expect this weekend (Friday-Sunday):

Wasatch Mountains above 7,000 ft: 1-2 feet
Wasatch mountain valleys/Wasatch Benches: 6-12″
Valleys of Wasatch Front: Up to 6″

Maybe more importantly, the weather will be very cold from Friday through early next week and will allow resorts to make snow around the clock if they so choose. Models trying to figure out the overall pattern beyond the next 7 days, but right now it’s looking like we may be at least clipped by another system mid-next week.

Details will continue to iron themselves out so stay tuned . . .


P.S. We have added a Glossary link to our “Resources” page. Please utilize this if you have any questions regarding some of the weather terms mentioned in the discussion.

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4 thoughts on “Less than 24 hours ’til liftoff

  1. Prior Air Force Wx Gal

    Thanks a lot for your informative discussions! As a prior weather forecaster and now stationed out here at Hill AFB with our little family, I certainly enjoy reading your blog! The weather here in Utah is awesome! We love the changing seasons! Let it snow!!!!

  2. dante

    Just heard the national news say, ” the toughest thing to predict is the snow totals”. Thank you, WSF, for being the first to take a risk and give us a snow total forecast several days out.

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