Friday, January 27, 2012

Headscratcher Snowband

One of the more interesting aspects of last-nights storm was an intense wind-parallel band that developed as the frontal band moved out of the region.

The band developed shortly after 0300 UTC (0800 PM MST) and persisted for about 3 hours.  It formed over the southeast corner of the Great Salt Lake, extended over the mountains north and east of the University of Utah, and into the eastern Uinta Mountains.  Greatest impacts were probably along I-80 between Kimball Junction and Coalville.  Tragically, the band largely missed the central Wasatch, as suggested by the 0419 UTC (0919 PM MST) radar image below.

What processes led to the development of this isolated, wind-parallel band?  700-mb temperatures were about -4ºC in the 0000 UTC sounding.  Perhaps lower it some to -7ºC for a couple hours later.  Lake temperature perhaps -2ºC.  Thermodynamically, this isn't a situation where we would expect lake effect.  Some digging is needed to understand this event.


  1. Looks like upstream orography (as per Trevor's last presentation in the department) is playing a bigger role than is traditionally thought!

  2. Surface obs implied a low-level convergence zone oriented NW-SE across the lake which might have led to this band. There was significant westerly surface wind component to the south/west of this zone, with light winds and temps a few degrees cooler on the north/east side. It seems like the Promontory Peninsula may have played a role in channeling the surface winds and focusing the convergence, with the band development perhaps initiating near Promontory Point and radar echoes appearing further downwind.