Comparison of a modified 18z NUCAPS sounding in far southern MN suggested a fairly accurate temperature profile (surface temperatures in southern MN were warmer than up at MSP.). NUCAPS did miss a pronounced dry layer around 700 mb, while it was too dry higher up especially around 500mb.
We also noticed some erroneous gridded NUCAPS precipitable water data round 16z across the Midwest (values of 3 to 4 inches). These looked more reasonable with the pass at 18z.
There was also 120 to 150% 850mb and 925mb RH.
The only satellite pass around that time was Metop-A. While the soundings were yellow, they generally were ok and didn’t match the gridded data.
– Barry Allen