Long duration event set to affect Wasatch range (UPDATED Sat. 11/20)

By:  Lionel Hutz
November 20, 2010 11:00 am | Category: Weather

In the latest round of our weekly series entitled “Hey- it snows a lot in the Wasatch” we will feature a long duration event. From Sunday until Tuesday of next week a large western trough will swing into the intermountain region and bring a prolonged period of mountain snowfall.

Saturday 11/20/10 Update

Things are looking still very good for a large and wet pacific storm to impact the Wasatch range over the next 96 hours. Starting today – later in the day- snow will begin to break out across the range along a sw flow. As the trough moves inland tonight, tomorrow snow will peak in intensity. High res gridded models show a very achievable 1.75 to 2.25 liquid equivalent precipitation by around midnight sunday. Then, as the trough moves over the great basin, a break in the snowfall should be ended by an unstable westerly flow. The latest time height diagram shows a good saturation of water vapor and pretty decent lapse rates from monday evening through at least Wednesday morning. With the orographic lifting the western slopes of the Cottonwoods should do very very well. Another 1 to 2 inches of liquid equivalent are very possible. Notably I use liquid equivalent here because with the steep vertical motion and sw flow gruapel is very likely in the first 1/2 of the storm. Accordingly total snow depth will be a little tougher to judge as graupel doesn’t really pile up.

YAY STORMS!!

ORIGINAL DISCUSSION

As we move into the weekend a large pacific trough will deepen as it swings down out off the coast of the California. As it deepens and swings into california and the west it will bring with it upper level divergence and an unstable moist airmass. Overall the system will first bring precip on a south west flow, then as the trough moves through region it will bring precip enhanced by a western flow. Precip will begin on sunday and last through at the least tuesday.

The models have a very clear that the first precipitation should begin later in the day sunday:
Trough deepening

Then the trough moves in full bore by Sunday.

As we can see clearly the beginning of the event will feature snow on a strong S/W flow. 24 hours later the strongest upper level divergence will spike as the trough remains it’s eastward progression through the intermountain west. Clearly the models have picked up on this and spiked the precip. rates in the central wasatch.

Once the trough flattens out, a moist airmass will persist. As the trough moves east, the flow will turn westerly. Given the moist airmass and the western flow, precip should remain over the Wasatch on Monday into Tuesday

And still persisting….tuesday into Wednesday.

Looking at the higher resolution time-height series for Alta-UT shows the long duration event with two spikes of upward motion that co-incide with the heightened model periods of precip- sunday night into monday and tuesday.

Adding all this up I’d suspect upper cottonwoods storm totals to reach 2-3 feet with more possible if the western flow remains steady and the vertical motion matches up.

11/18/10 Update

Models are  a little more progressive and show snow breaking out later in the day on saturday across the wasatch.  With Omega values greater than -6 likely there will be adequate instability.  Upward Vertical motion is also wvery high with spikes Sunday afternoon and night and then again tuesday early morning.  All in all things look good. 

Totals still look around 3 feet in the Cottonwoods.  However this will have to be updated when the High Res. models come in range over the weekend.

Should be a great opening weekend at Alta!

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Related Stuff:

  1. Upslope event of debatable strength set to affect North Country (Updated 2/20/10)
  2. Weekend Snows to Affect Wasatch (UPDATED ..WITH TOTALS)
  3. Long Range Thoughts: Sniffing out a Mid-Month Storm (Updated 1/16/10: Chances for significant snowfall increasing for So. VT)
  4. Wasatch Weather: Another Major Storm on the Way (UPDATED…Possible WTF))
  5. Wasatch Watch: Storm on Way for Veterans Day (Updated Totals)
  6. Long Range Thoughts: Are we in for a deep freeze?

6 Comments

  1. icelanticskier
    wrote on November 18th, 2010 at 7:58 am  
    1

    hmmmmm, wonder when high-dry time comes. bound to happen. with the wonderful start there, me thinks april could be a very good time to visit foofyland. folks will have had enough by then.

    thanx for the updates!

    rog

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  2. Patrickm
    wrote on November 19th, 2010 at 4:11 pm  
    2

    This forecast is perfect for a sea-level dweller like me! I’ll be up there from Tuesday through the Thanksgiving weekend and this looks to be the best Thanksgiving week skiing in years! Alta opened up today with 89 trails…now that’s an opening! NWS Salt Lake is thinking 3-4 feet is possible by Wednesday morning in the cottonwoods. Only problem is it will be COLD, below zero temps likely in the morning Tuesday-Thanksgiving day with highs only in the teens. Crossing my fingers this all plays out like forecasted!

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    • bottleman
      wrote on November 19th, 2010 at 5:45 pm  
      3

      You’re not really complaining about the cold, are you?!

    • Patrickm
      wrote on November 19th, 2010 at 5:57 pm  
      4

      Not complaining, just temps that cold catch my eye because I live in Louisiana most of the year! I’m just thrilled there will be great snow and can’t wait to get out there!

  3. icelanticskier
    wrote on November 20th, 2010 at 9:06 am  
    5

    hopefully you’ll be able to get to it……..

    rog

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