Wednesday, November 24, 2010

Record cold and lessons for DLE forecasting

The 12Z KSLC sounding is now available and it came in with a 700 mb temperature of -23.3C, which is the lowest observed in November since at least 1956.

It is presently 14F at KSLC, -3 at Alta Base, and -17 on top of Mount Baldy.  Don't be fooled by the warm temperatures downstream of the GSL and in the northern Salt Lake Valley where there's some cloud cover.  It is much colder in the southern Salt Lake Valley, Tooele Valley, Rush Valley, and West Desert.  Especially cold spots in the valleys include Bluffdale (1F), and Clover (-13F).

With regards to the Dreaded Lake Effect, the wimpy stuff in the radar above has developed in the last hour or two and represents all that we got last night.  Yeah, we had a HUGE lake-700-mb temperature difference, but check out how dry the boundary layer is in the KSLC sounding above.  No matter how big the lake-700-mb temperature difference is, you still need additional ingredients to bake the lake-effect cake.  Without those ingredients, increasing the lake-700-mb temperature difference is like taking an additional vitamin C pill in the morning when what you really need is some B-12 to go with it.  Making this even more difficult is that the models still struggle forecasting those ingredients - especially moisture.  I haven't verified this carefully, but a quick look at forecast and observed soundings suggests that we came in drier than yesterday's NAM suggested.


  1. I noticed that the recent models have coldest air staying well to the north... now forecasting a 700-mb temp of -21 C instead of -24 or -25 over SLC for 00Z this afternoon as suggested a couple days ago. Some of the earlier runs showed the coldest of the air mass (over Montana and southern Alberta) wrapping back around a deep trough centered near eastern Idaho today. Now it looks like the coldest air remains east of the Continental Divide instead, so obviously we didn't get our record low maximum.

  2. It's a record at 700 mb, but that's not where the people live.

    Does anyone know the record low maximum for today? What are the records for November, today, and tomorrow?