Tuesday, December 22, 2015

Santa Delivers Something for Everyone

We may be amateurs, but every now and then we pull the government weather-control levers and get it right.  Despite a brief lull yesterday evening that briefly caused many of my friends to text or e-mail me to ask if the storm was over (no, it wasn't), this storm has has provided Christmas presents for all you girls and boys. Let's start with some water totals since 5 AM yesterday from automated sensors that report to MesoWest:

Northern Wasatch
Ben Lomond Peak: 3.3" (through 6 am)
Ben Lomond Trail: 2.1" (through 6 am)
Snowbasin Middle Bowl: 2.35" (through 7:15 am)

Central Wasatch
Alta-Collins: 1.01" (through 7 am)

I'm seeing some widely disparate SNOTEL measurements in the central and southern Wasatch depending on if the gauge or pillow measurement is used, so I'm not using them here.  Snow reports in Park City and Big Cottonwood Canyon, however, are much higher than those in Little Cottonwood Canyon, so it's safe to assume that Alta-Collins is one of the drier spots in the storm so far and that higher water totals were observed elsewhere.  Ditto for the southern Wasatch where the Utah Avalanche Center has raised the avalanche danger to extreme with 3.7" of water equivalent falling at 7500 feet in the mountains near Provo.  Given that Alta and Snowbird have been on top in most every storm so far this year, it seems only fair that socialist Santa spreads the wealth a little bit in this storm.

The latest radar loop [1114-1432 UTC (0414-0732 MST)] shows a nearly solid wall of returns upstream of the Wasatch Front with precipitation enhancement along much of the Wasatch Range in the now west to west-northwest crest-level flow.  

Snow levels have dropped to the valley floor.  I had a white knuckle bus ride down from the Avenues this morning as the plows hadn't been out yet and roads were snow covered with that slick snot that you get after the transition from rain to snow.  Kudos to my UTA driver for an expert descent down Virginia Street!

The models keep us in a fairly moist west to west-northwest crest-level flow through tomorrow afternoon.  Although there could be a break or two in there, it appears accumulations in the mountains will continue to be substantial.  Further, the valleys are going to see accumulations as well, ensuring a White Christmas for nearly everyone, unless someone gets skunked in a localized precipitation shadow (although that's looking unlikely).  

Let's start again with the experimental high-resolution NCAR ensemble.  Accumulations below are from 0000 UTC (1700 MST) yesterday afternoon through 0000 UTC (1700 MST) tomorrow afternoon, so keep in mind that these numbers do include last night's forecast.  Mean water totals in the central Wasatch exceed 2 inches and in the northern Wasatch are generally greater than 1.5 inches.  

The forecast plume for Snowbasin below shows the heavier precipitation last night, after which accumulation rates back off a bit through tomorrow afternoon.  From about 1200 UTC (0500 MST) this morning to 0000 UTC (1700 MST) tomorrow afternoon the total accumulation is about an inch for most members.  

At Alta Collins, the total accumulation from 1200 UTC (0500 MST) this morning to 0000 UTC (1700 MST) tomorrow afternoon ranges from 0.8 to 1.7" depending on the member.  

Given the predominantly westerly to northwesterly flow, the base of Park City probably won't do as well as yesterday, but they will get some.  The total accumulation from 1200 UTC (0500 MST) this morning to 0000 UTC (1700 MST) tomorrow afternoon is 0.4" to perhaps 0.7".  

I might drop the numbers for Snowbasin and Alta-Collins just a bit, but by and large, these water numbers look to be a pretty good hack.  For the period from 1200 UTC (0500 MST) today through 0000 UTC (1700 MST) tomorrow afternoon, let's go with 0.75-1.25 inches of water for the northern Wasatch and 1-2 inches of water for the upper Cottonwoods.  In town, Park City won't do as well as yesterday, but you'll still get some, although clearly Santa's socialist streak is over.

For the valley?  Ah, you're on your own for that.  I don't have the time!


  1. As expected Timpanogos/Sundance has been the big winner with right around 4.5" water from this storm so far! http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=slc&sid=SNM&num=48&raw=0&dbn=m&banner=header If there a a weather station higher up on Timpanogos I would not be surprised to see over 5.00" water!

  2. So where does this put us in terms of year to date of average snowfall for say Alta or Brighton? Seams like height of snow might be largest in upper BCC...

  3. I was having a hard time finding year to date average snowfall for a certain date. Do you use Meso West?

    1. Use this: http://www.wcc.nrcs.usda.gov/webmap/index.html#elements=&networks=!&states=!&counties=!&hucs=&minElevation=&maxElevation=&elementSelectType=all&activeOnly=true&hucLabels=false&stationLabels=&overlays=&hucOverlays=&mode=data&openSections=dataElement,parameter,date,elements,location,networks&controlsOpen=true&popup=&base=esriNgwm&lat=39.98&lon=-98.96&zoom=4&dataElement=WTEQ&parameter=PCTMED&frequency=DAILY&duration=I&customDuration=&dayPart=E&year=2015&month=12&day=21&monthPart=E

      Snowpack is the more important quantity rather than snowfall.

    2. Yo Ty,

      Alta has a pretty great snowfall history function on their website:


  4. Someone sent me a link to an interesting article on the "bomb" cyclone development over the Bering Sea this past weekend. I mention this because our current storm cycle appears to be in large part related to the remnants of this giant north Pacific cyclone.


    1. I'm sure there was a linkage, but I haven't had time to investigate.

    2. Actually I may have made a mistake, looks like it happened the previous weekend, so maybe no direct linkage. Although there was another huge cyclone (probably larger in size) over that area this past weekend. The article is interesting in any case.