Wednesday, November 25, 2015

This Storm Could Be a Turkey

Ah, it's a beautiful morning in Salt Lake.  The sun is shining.  Temperatures are around 50ºF.  Gorgeous.

The loop below shows very nicely the situation that has proven to be the bane of forecasters for so long.  As mentioned in earlier posts on this event, we have a situation of large-scale Rossby-wave breaking, with the upper-level trough forming rapidly over the Pacific States overnight last night.

All the action right now is to our north and west, although it's less impressive than I hoped it would be prior to moving into the Wasatch Front (thinking from a skier's perspective here, not a commuter's).  Each successive model run slows the system down a bit more and that continued to be the case through this morning.  Here's yesterday's NAM time-height for Salt Lake City showing frontal passage around 2100 UTC (2 PM MST) this afternoon, as well as a slug moisture in the pre-frontal southerly flow for this morning and the early afternoon.

Now here's today's.  Frontal passage is after 0000 UTC (5 PM MST) and the prefrontal environment is much drier.

Snow will eventually kick in later this afternoon over the mountains, but totals by tomorrow morning are going to perhaps only be in the 3-6 inch range in the upper Cottonwoods.  I haven't been putting any numbers on this event over the past few days as it seemed so hopelessly unpredictable, as we have discussed at length in early posts, so there's always the hope that I'm overly pessimistic, but I doubt it.  Right now, I think we'll escape the evening rush hour along the Wasatch Front without major weather problems, but keep an eye on things just in case.


  1. Who the heck keeps doing the no snow dance....

  2. The good old WRF-GFS out of the University of Washington has been showing this for several days now, love that model but not happy about the low snow totals.

  3. Why wouldn't the huge low associated with the hurricane off Mexico stall the eastward progression and pull the storm system now in the NW further south? Slower passage, more snow.

    (Please remember, I'm a Harvard lawyer, not a UofU sno guru -- give me a break and some understanding of Wasatch Weather -- which, after all, is why I retired and moved out here.

    Tommy T.

  4. How come the NAEFS snow forecast is still showing crazy high snow totals? It sounded like from your DIY forecast tools description that if anything the NAEFS should underestimate the snow since it doesn't resolve lake effect etc. very well.

    1. We don't really know what the NAEFS biases are. We're working on that at the moment. Not resolving lake effect is only one source of bias. Sorry if that writeup wasn't clear.

      I would probably expect based on subjective experience that the snowfall forecasts are probably overdone. Also, humans have a habit of looking at the higher members of the forecast ensemble, which contributes to subjective bias.