A well defined TROWAL feature that set up over the high plains from eastern NM into western TX and KS on December 21, 2013 was captured very well by the NESDIS snowfall rate product. A composite radar reflectivity loop in the first image below summarizes the overall evolution of this feature between 12 UTC on December 21st and 00 UTC on the 22nd (click image to loop and enlarge). Initially temperatures were too warm for snow across much of the area however as a potent cold front shifted south over the region rain changed over to snow. In the area of greatest instability the snow became heavy at times from near Tucumcari, NM (KTCC) to Dalhart, TX (KDHT).
The following series of images compare hourly precipitation reports at several sites across western TX and KS with the NESDIS snowfall rate product. The first image was captured at 2040UTC and the AWIPS cursor readout at KDUX (Dumas, TX) is shown. Note the observation is reporting an hourly precipitation accumulation of 0.05 (P0005) with moderate snowfall and a visibility of 1/2SM. The cursor readout comparison with the QPE product is 0.0544 in/hr. The following sample point valid for KPYX (Perryton, TX) is reporting a visibility of 1/4SM however no weather or precipitation is available since it is only an AWOS. However, the QPE product is sampling a precipitation rate of 0.1064 in/hr which converting with a simple 10:1 snow ratio would equate to heavy snow at 1″ per hour. The next image was captured at 2236UTC and the cursor readout at KDDC (Dodge City, KS) is shown. Note the observation is reporting an hourly precipitation accumulation of 0.07 (P0007) with moderate snowfall and a visibility of 1/2SM. The QPE comparison in the readout shows a rate of 0.092 in/hr. These values are exceptionally representative of the current conditions and the latency is less than 30 minutes.
After the storm system pulled out of the region the Snow-Cloud RGB product provided a stellar view of this mesoscale band of snowfall. Modifying temperatures over the following days significantly eroded snowpack in most areas except where the heaviest snow fell. Local storm reports obtained from the Iowa State website indicated between 6 and 11 inches of snow impacted the area within the central axis of the TROWAL feature.